australian population studies 2018 | volume 2 | issue 2 | pages 1–2 © wilson, charles-edwards and corcoran 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org editorial introduction to the special section on australia’s population policy tom wilson* charles darwin university elin charles-edwards the university of queensland jonathan corcoran the university of queensland *corresponding author. email: tom.wilson@cdu.edu.au. address: northern institute, charles darwin university, ellengowan drive, darwin, nt 0909, australia published on 12 november 2018 this issue of australian population studies includes a special commentary section on australia’s population policy. population issues and population policy debates periodically find themselves in the political and media spotlight, and recent months have seen a resurgence of interest in these topics. in part this attention was the result of australia’s population officially passing the 25 million milestone in early august (abs 2018), though population issues had been gaining momentum from earlier on in the year. a number of politicians and well-known figures have advocated for lower immigration and lower population growth, with relatively few voices supporting current or higher growth rates. while much attention has, as usual, focused on annual net overseas migration totals and the overall growth rate of the population, on this occasion many commentators have also expressed concern about the growth rates of melbourne and sydney, and argued for a greater proportion of immigrants to be directed away from those centres. sensing the increased political sensitivity of the issue, the australian government created a new minister for cities, urban infrastructure and population in addition to the established portfolio of immigration, citizenship and multicultural affairs as part of the cabinet reshuffle accompanying the change in prime minister in august (parliament of australia 2018). many will be watching for population-related policy announcements from these ministers with interest, particularly in the lead-up to the next federal election. in the special commentary section of this issue three australian demographers present their responses to the question ‘what sort of population policy should australia adopt?’ (if any). the purpose is to add some academic perspectives to the wide-ranging population policy debate. all contributions underwent the same double-blind reviewing process applied to regular journal papers. peter mcdonald argues that australia already has a comprehensive de facto population policy and that the country should retain it until at least 2026, especially in light of the labour supply crunch coming in the next decade. nick parr sets out the case for australia to adopt an official population policy and focuses particularly on the skilled stream of the migration program. importantly, he also calls for more research on demographic issues to build up a more comprehensive evidence base for australia’s population policy. liz allen also argues for an official population policy which eschews http://www.australianpopulationstudies.org/ mailto:tom.wilson@cdu.edu.au 2 editorial: wilson, charles-edwards and corcoran australian population studies 2 (2) 2018 demographic targets and instead emphasises the wellbeing of individuals and communities, and long-term sustainability. references australian bureau of statistics (abs) (2018) australia's population to reach 25 million. media release. http://www.abs.gov.au/ausstats/abs@.nsf/mediareleasesbyreleasedate/c3315f52f6219de9c a2582e1001bc66a?opendocument. accessed on 8th october 2018 parliament of australia (2018) current ministry list: the 45th parliament. https://www.aph.gov.au/about_parliament/parliamentary_departments/parliamentary_library/ parliamentary_handbook/current_ministry_list. accessed on 8th october 2018. http://www.abs.gov.au/ausstats/abs@.nsf/mediareleasesbyreleasedate/c3315f52f6219de9ca2582e1001bc66a?opendocument http://www.abs.gov.au/ausstats/abs@.nsf/mediareleasesbyreleasedate/c3315f52f6219de9ca2582e1001bc66a?opendocument https://www.aph.gov.au/about_parliament/parliamentary_departments/parliamentary_library/parliamentary_handbook/current_ministry_list https://www.aph.gov.au/about_parliament/parliamentary_departments/parliamentary_library/parliamentary_handbook/current_ministry_list australian population studies 2018 | volume 2 | issue 2 | pages 59-61 © reimondos, gray and evans 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org how moving a box changed the religious landscape of australia anna reimondos* australian national university edith gray australian national university ann evans australian national university * corresponding author. email: anna.reimondos@anu.edu.au. address: school of demography, anu college of arts and social sciences, the australian national university, 9 fellows road, acton, act 2601, australia paper received 1 june 2018; accepted 20 july 2018; published 12 november 2018 this data visualisation is the winner of the australian population studies 2018 population data visualisation competition, kindly sponsored by geografia pty ltd. in this data visualisation we use the 2011-2016 australian census longitudinal dataset (acld) to examine how answers to the question on religious affiliation changed between 2011 and 2016. a question on religious affiliation has been included in every census since the first national census of 1911. it is the only question in the census which is optional, as outlined in the census and statistics act 1905, and it is also the question that has arguably attracted the most controversy over the years. up until 1991 the question on religion was in the form of an open text question. in 1991 the format changed to pre-defined check boxes listing several main religions including catholic, anglican (church of england) and uniting church. the check boxes were followed by a space for an open-text answer where people could write any ‘other’ religion that was not included in the pre-defined list. finally at the bottom was a check box for ‘no religion’. although the content and order of the pre-defined list of religions changed between 1991 and 2011, in all years up to and including 2011 ‘no religion’ was always on the bottom after ‘other’. in a public consultation on the content of the 2016 census, nearly half of the 915 submissions related to the question on religious affiliation (abs 2013). following a review, the format of the question changed and for the first time in 2016 ‘no religion’ was placed at the very top of the list of predefined religions. although the percentage of australians identifying as not having a religion has been increasingly steadily since the first census in 1911, between 2011 and 2016 the percentage stating ‘no religion’ increased dramatically from 22.3% to 30.1%. this 35% increase is significantly higher than the 20% increase between 2006 and 2011 and the 19% increase between 2001 and 2006. to observe the change in behaviour following the re-formatted question in the 2016 census we used the acld, which is a representative 5% sample (1.2 million records) from the 2011 census linked to the corresponding records from the 2016 census. we used the abs tablebuilder to cross-tabulate people’s responses to the religion question from 2011 and 2016. this table was re-formatted in stata d em og ra ph ic http://www.australianpopulationstudies.org/ mailto:anna.reimondos@anu.edu.au 60 reimondos, gray & evans australian population studies 2 (2) 2018 to create an individual record of each combination of possible religions in 2011 and 2016. the data was then inputted to and open source data visualisation framework at rawgraphs1. the resulting svg code was then further edited to create the desired image. the visualisation is shown in figure 1. on the left of the diagram is the distribution of religious affiliation in the 2011 census, in order of magnitude, and on the right are the answers given in 2016. in 2011, catholic was the dominant religious affiliation answered by 26% of the acld sample. in 2016 ‘no religion’ had become the prominent religious belief with catholics in second place. census respondents who answered ‘no religion’ in 2016 had previously identified with a wide variety of other religions. not surprisingly, the majority of those stating ‘no religion’ in 2016 had also stated ‘no religion’ in 2011. however among those who did state a religion in 2011, the percentage who switched to ‘no religion’ varied considerably. for example only 11% of those who previously stated they were catholic chose ‘no religion’ in 2016. in contrast a fairly large proportion (21%) of anglicans changed to ‘no religion’. of those who did not state a religion in 2011, just under half (46%) chose ‘no religion’ in 2016. for some religions such as eastern orthodox, islam and hinduism only a small proportion switched to ‘no religion’. for questions involving unordered categorical responses, such as the religion question in the census, the order in which the options are presented has been shown in previous research to be important. the primacy effect suggests that people may choose the first acceptable answer presented to them, particularly if the list of response categories is long (tourangeau et al. 2000). evidently the change in question format, and moving the box titled ‘no religion’ to the top of the list of pre-defined options had a significant impact on the way in which the 2016 question on religious affiliation was answered. references abs (2013) census of population and housing: consultation on content and procedures, 2016. catalogue no. 2007.0. canberra: abs. tourangeau r, rips l j, and rasinski k (2000) the psychology of survey response. cambridge: cambridge university press. 1 http://app.rawgraphs.io australian population studies 2 (2) 2018 reimondos, gray & evans 61 figure 1: answers to the question on religion in the 2011 and 2016 censuses source: australian bureau of statistics, 2011-2016 australian census longitudinal dataset australian population studies 2018 | volume 2 | issue 1 | pages 52–55 © trauer, freak-poli, kippen and mcneil 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org fifty years of plummeting cardiovascular death rates and implications for the individual james m trauer* monash university rosanne freak-poli monash university rebecca kippen monash university john mcneil monash university * corresponding author. email: james.trauer@monash.edu.au. address: epidemiological modelling unit, school of public health and preventive medicine, monash university, 553 st kilda road, melbourne, victoria 3004 paper received 5 march 2018; accepted 26 march 2018; published 28 may 2018 mortality rates have been reliably reported for many decades and provide important insights into major changes in disease burden or ‘epidemiological transitions’ (freak-poli, bi and hiller 2007; omran 1977). here we present illustrations of the dramatic shift from cardiovascular disease to cancer as the leading cause of death in australia and highlight the significance of these changes for individual australians. we obtained data on the total number of deaths and population size for the period 1907–2014 in australia from the general record of incidence of mortality (grim) books (australian institute of health and welfare 2017) and used this information to calculate death rates overall and by age group attributable to all causes, cardiovascular disease and cancer. the small proportion of deaths (generally <0.1%) for which age group was missing were assumed to be distributed as for the deaths for which age group was known. these calculated death rates were used to construct life tables, under which the complement of the all-cause mortality rate for each year was used to determine the number of persons surviving to the following year. as the data are grouped into five-year age groups, karup-king interpolation (siegel and swanson 2004) was used to obtain smoothed estimates for each year of age in the construction. full methods are presented as publicly available python 2.7 code at https://github.com/jtrauer/demography. we observed dramatic falls in cardiovascular mortality, with cancer overtaking cardiovascular disease as the leading cause of death category at the start of this century (figure 1, left panels). the fall is even more impressive when presented on a log-scale, because the steady absolute decrease represents a greater proportional decrease as rates decline. cardiovascular death rates are steadily falling across all age groups, although the youngest age brackets have the greatest variation due to the noise associated with these very low rates (figures 1, right panels). while the initial reduction in cardiovascular mortality was attributable to reductions in death rates in young adults and middle age, increasingly the falls in death rates are occurring in older age groups. although the fall appears less impressive in the oldest age bracket (85 years and above), this is attributable to the decline in death rates being offset by an increase in the age distribution of this age group. d e m o g ra p h ic http://www.australianpopulationstudies.org/ mailto:james.trauer@monash.edu https://github.com/jtrauer/demography australian population studies 2 (1) 2018 trauer j, freak-poli r, kippen r and mcneil j 53 figure 1: death rates by cause and cardiovascular death rates by age group from 1964–2014 in australia source: australian institute of health and welfare (2017). notes: left two panels show death rates standardised to the age structure of the australian bureau of statistics standard australian population 2001. right two panels show age-specific death rates attributable to cardiovascular disease. these changes have translated into massive changes in survival and cause of death (figure 2). for example, a person subject to the age–cause-specific death rates of 1964 would probably be dead before their 80th birthday, with cardiovascular disease the likely cause of death. by contrast, a person subject to the age–cause-specific death rates of 2014 would probably live to celebrate their 85th birthday, and likely die of non-cardiovascular causes before turning 90. again note that death rates for those aged 85 years and above are considered as a single age group, which was used to calculate survival from 85–89 years. therefore, our findings emphasise the need for disaggregation of this oldest age group, which has grown from a very small group to a considerable size, and continues to grow. past modelling in similar developed country settings suggests that the dramatic reductions in cardiovascular mortality are attributable both to changes in the population prevalence of predisposing risk factors and medical treatments – the latter including both clinical care for episodes of disease and secondary prevention (capewell et al. 2000; capewell, morrison and mcmurray 1999). pharmacological primary prevention has not contributed significantly to these major reductions in the past, although results from large community-based randomised controlled trials into aspirin (aspree investigator group 2013) and statins (zoungas et al. 2014) as primary preventive interventions will shed light on this potent. however, while intervention studies can quantify the 54 trauer j m, freak-poli r, kippen r and mcneil j australian population studies 2 (1) 2018 relative reduction in incident cardiovascular disease, one of the most important issues to address before recommending prevention strategies to individuals is the absolute risk of new cardiovascular disease (otto 2016). while disease-specific mortality rates do not translate directly to rates of incident disease, the dramatic reductions in cardiovascular death rates over recent decades are likely to reflect decreases in cardiovascular disease to some extent. therefore, it is essential to ensure guidelines are based on risk assessments that consider modern rates of incident cardiovascular disease by demographic and comorbidity status. cancer mortality is presented for comparison as it is the other major disease category responsible for a high proportion of deaths over recent decades. although cancer mortality appears relatively stable over this period, the aggregate rates mask important underlying trends in cancer types by gender (freak-poli, bi and hiller 2007 with non-cardiovascular mortality remaining relatively stable, it is clear that the declines in overall mortality directly parallel those in cardiovascular-specific mortality (figure 1, upper left panel). this highlights how critical these improvements have been in driving australia’s recent improvements in overall life expectancy, to the extent that falling cardiovascular mortality has entirely driven the all-cause mortality decreases. figure 2: cumulative outcomes for an australian living their life with death rates as observed in 1964, 1989 and 2014 source: australian institute of health and welfare (2017). notes: survival region represents a life-table, with cumulative contributions of three cause of death categories presented as shaded regions above. data from five-year brackets are smoothed by calculating yearly estimates using karup-king interpolation. australian population studies 2 (1) 2018 trauer j, freak-poli r, kippen r and mcneil j 55 references aspree investigator group (2013) study design of aspirin in reducing events in the elderly (aspree): a randomized, controlled trial. contemporary clinical trials 36(2): 555–564. https://doi.org/10.1016/j.cct.2013.09.014. accessed on 24 january 2018. australian institute of health and welfare (2017) general record of incidence of mortality (grim) books. https://www.aihw.gov.au/reports/life-expectancy-death/grim-books/contents/grim-books. accessed on 25 january 2018. capewell s, beaglehole r, seddon m and mcmurray j (2000) explanation for the decline in coronary heart disease mortality rates in auckland, new zealand, between 1982 and 1993. circulation 102(13): 1511–1516. http://www.ncbi.nlm.nih.gov/pubmed/11004141. accessed on 16 august 2018. capewell s, morrison c e and mcmurray j j (1999) contribution of modern cardiovascular treatment and risk factor changes to the decline in coronary heart disease mortality in scotland between 1975 and 1994. heart (british cardiac society) 81(4): 380–386. http://www.ncbi.nlm.nih.gov/pubmed/10092564. accessed on 16 august 2018. freak-poli r, b p and hiller j e (2007) trends in cancer mortality during the 20th century in australia. australian health review 31(4): 557–564. omran a r (1977) epidemiologic transition in the united states: the health factor in population change. population bulletin 32(2): 1–42. http://www.ncbi.nlm.nih.gov/pubmed/12335110. accessed on 2 march 2018. otto c m (2016) statins for primary prevention of cardiovascular disease. british medical journal (clinical research edition) 355: i6334. https://doi.org/10.1136/bmj.i6334. accessed on 24 january 2018. siegel j s and swanson d a (2004) the materials and methods of demography. uk: emerald group publishing limited. zoungas s, curtis a, tonkin a and mcneil j (2014) statins in the elderly. current opinion in cardiology 29(4): 372–380. https://doi.org/10.1097/hco.0000000000000082. australian population studies 2017 | volume 1 | issue 1 | pages 1–2 © wilson, charles-edwards and corcoran 2017. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org editorial introducing australian population studies tom wilson* charles darwin university elin charles-edwards the university of queensland jonathan corcoran the university of queensland *corresponding author. email: tom.wilson@cdu.edu.au. address: northern institute, charles darwin university, ellengowan drive, darwin nt 0909, australia published on 20 november 2017 welcome to this inaugural issue of australian population studies. the aim of the journal is to disseminate and promote high-quality peer-reviewed research which extends our knowledge and understanding of population issues in australia. in doing so, we wish to become the leading publication for australian population research. importantly, australian population studies is open access, online and does not charge fees of any kind. academic publishing is witnessing a growth in open access journals, and we are pleased to be part of this growing movement. the benefits are numerous. it brings greater visibility and impact for research, with several studies concluding that open-access papers are cited more (e.g. atchison and bull 2015; wagner 2010, 2016; wang et al. 2015). where research has been funded by the taxpayer it is available without readers having to pay further to access findings. research is also readily available to practitioners, policy makers and members of the public who typically do not have access to subscription journals, as well as to academics in countries which cannot afford such journals. all content in australian population studies is not only open access, but may be reproduced elsewhere. it is published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au), which means content may be shared and reproduced for noncommercial purposes providing the authors of the work are fully acknowledged. authors are welcome – and in fact are strongly encouraged – to upload papers published in australian population studies to researchers’ social networking sites such as researchgate. our expectation is that there will be two issues per year, published in may and november, though the annual number of issues may be reviewed in the future. the latest dates for the submission of contributions are 15th january for the may issue and 15th july for the november issue, offering relatively fast submission-to-publication turnover. contributions consist of three main types. first, we publish short research papers which should not exceed 4000 words. we do not carry full-length papers. traditional population issues, contemporary ‘hot topic’ demographic debates, policy-relevant studies, local case studies, new population datasets and relevant software and code are all suitable topics for research papers. supplementary files of data, code, detailed results and similar can accompany papers. we particularly encourage papers focusing on ‘core’ demographic processes and patterns, such as fertility, mortality, migration, http://www.australianpopulationstudies.org/ mailto:tom.wilson@cdu.edu.au 2 editorial: wilson t, charles-edwards e and corcoran j australian population studies 1 (1) 2017 population ageing, household change, population distribution, relationships, families and population policy. sometimes demography and population studies can seem like a doughnut of specialised studies with relatively little filling in the middle! second, we encourage the use of data visualisation to present demographic data in interesting, new and innovative ways. these appear as demographics. we would like this to become a key element of the journal and will announce a data visualisation competition shortly. third, we publish introductory guides which consist of an introduction to demographic methods, approaches, data, theories or software which are not well covered in the textbooks. we hope these guides will be of use to students, researchers, practitioners, teachers and others wishing to learn about demography. the common requirement for all three types of contribution is that they should be written for a wide-ranging audience and not limited to academics. many people have generously given their time and expertise to make this first issue of australian population studies possible. we wish to extend our sincere thanks to all authors, reviewers, editorial advisory board members, our copy editor ros moye, our logo designer james daley, charles darwin university library, which is providing web hosting for the journal, and the northern institute at charles darwin university, which is providing financial support. we hope you enjoy reading the first issue. we welcome feedback (via the email address shown above). finally, we encourage researchers working on population issues in australia to submit contributions for future issues. submission guidelines are available at www.australianpopulationstudies.org/index.php/aps/about/submissions. references atchison a and bull j (2015) will open access get me cited? an analysis of the efficacy of open access publishing in political science. ps: political science & politics 48(1): 129–137. wagner a b (2010) open access citation advantage: an annotated bibliography. issues in science & technology librarianship (60), viewed 30 october 2017, http://www.istl.org/10winter/article2.html. wagner a b (2016) citation impact advantages of open access (oa) articles over non-oa articles – updated 12/21/2016 with 16 new 2015–16 studies, viewed 30 october 2017, https://ubir.buffalo.edu/xmlui/handle/10477/75108. wang x, liu c, mao w and fang z (2015) the open access advantage considering citation, article usage and social media attention. scientometrics 103(2): 555–564. http://www.australianpopulationstudies.org/index.php/aps/about/submissions http://www.istl.org/10-winter/article2.html http://www.istl.org/10-winter/article2.html https://ubir.buffalo.edu/xmlui/handle/10477/75108 australian population studies 2018 | volume 2 | issue 1 | pages 56–58 © wang, corcoran, liu and sigler 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org visualising the internal migration of the mainland china-born population between australian capital cities over time siqin wang* the university of queensland jonathan corcoran the university of queensland yan liu the university of queensland thomas sigler the university of queensland * corresponding author. email: s.wang6@uq.edu.au. address: school of earth and environmental sciences, chamberlain building, the university of queensland, st lucia 4072, queensland, australia paper received 1 march 2018; accepted 16 march 2018; published 28 may 2018 over the past three decades, migration from mainland china to australia has become increasingly significant. the 2016 australian bureau of statistics (abs) census of population and housing (census) recorded a total of 526,000 china-born migrants living in australia, accounting for 2.2 per cent of the total national population, ranking it as the largest non-commonwealth foreign-born group in the country (abs 2016a). drawing on data from three australian censuses, we visualise 5-year internal migration flows of the china-born population between australian state and territory capitals. data were retrieved online from tablebuilder pro for the 2006, 2011 and 2016 censuses (abs 2006; 2011; 2016a). the mainland china-born population was defined as those residing in australia who were born in the people’s republic of china but not the special administrative regions of macau and hong kong. capital cities were spatially defined as greater capital city statistical areas (abs 2016b). our demographic is a series of three directional circular plots (abel 2016) that depict the system of internal migration flows representing the relative size and direction of internal migration movements (figure 1, page 58). the plots were created using the r statistical software and employing the package ‘circlize’ (available at: https://www.r-project.org/about.html). the circular plots represent the volumes, origins and destinations using lines of varying width and colours to capture migration flows between capital cities (figure 1). the length of each segment for a given city represents the number of migrants moving to and/or from a particular capital. for each city the direction of migration flows is indicated by an arrow pointing from origins to destinations. each capital city and the flows originating from that city are represented by a single colour (e.g. sydney is depicted in red for each of the three plots). each tick mark on the perimeter of the circle is used to represent a total of 200 migrants. we exclude the least numerically significant 30 per cent of flows from each of the circular plots. excluding these smaller flows helps to enhance the visual clarity by focussing on the main residential migration movements. d e m o g ra p h ic http://www.australianpopulationstudies.org/ mailto:s.wang6@uq.edu.au https://www.r-project.org/about.html australian population studies 2 (1) 2018 trauer j, freak-poli r, kippen r and mcneil j 57 our demographic illustrates a number of interesting internal migration patterns over the decade to 2016. • the absolute volume of internal migration between capital cities has increased 340 per cent over the decade. this increase includes migration to and from the smaller capital cities of hobart, darwin and canberra, which did not have large china-born populations in earlier decades compared to the larger capitals of sydney and melbourne. • there appears to be some stability in the internal migration trends of china-born migrants over time. more specifically, the share of migration across capital cities has principally remained the same, with sydney the largest origin and destination followed by melbourne and then adelaide. • the proportion of overall flows by capital city shows little change over time in sydney, melbourne and canberra. however, brisbane’s in-migration flows of the china-born population increase substantially over the period to 2016, reflecting a growing chinese community in brisbane and sustained migration from the other capital cities – in particular sydney and melbourne. an increase in out-migration flows is observed in both adelaide and hobart, especially over the period 2011 to 2016. out-migration from adelaide, especially in the period 2011 to 2016 may be tied to a relatively weaker job market and economic outlook (adzuna 2016; beer 2008). • sydney and melbourne both remain the largest destinations for china-born migrants. the attraction of these two cities over the other australian capitals for china-born migrants is arguably a function of denser social ties allied with a broader range of economic opportunities. there is a need to deepen our understanding of the internal migration patterns of the china-born population by capturing these movements at a range of spatial scales and unpacking the reasons under-pinning these flows. with such knowledge we will be able to better understand internal migration pathways after settlement, and how these pathways mesh with longer-term integration in australian society. acknowledgements an earlier version of this visualisation was presented at the institute of australian geographers conference in brisbane, july 2017. we thank the organisers and participants for their comments. we also thank karen borchardt at the university of queensland for help with the data collection. references abel g (2016) updated circular plots for directional bilateral migration data. https://gjabel.wordpress.com/tag/circular-plot/. accessed on may 2016. abs (australian bureau of statistics) (2006) census of population and housing – fact sheets, 2006. cat. no. 2914.0. canberra: abs. abs (2011) census of population and housing: outcomes from the 2011 census output geography discussion paper. cat. no. 2911.0.55.003. canberra: abs. abs (2016a) migration, australia, 2015–16. cat. no. 3412.0. canberra: abs. abs (2016b) australian statistical geography standard: volume 1 – main structure and greater capital city statistical areas. cat. no. 1270.0. canberra: abs. adzuna (2016) australia job market report. https://www.adzuna.com.au/blog/wpcontent/uploads/2016/03/adzuna-march-job-report-robots-by-20301.pdf. accessed on march 2016. beer a (2008) risk and return: housing tenure and labour market adjustment after employment loss in the automotive sector in southern adelaide. policy studies 29(3): 319–330. 58 wang s, corocan j, liu y and sigler t australian population studies 2 (1) 2018 source: abs 2006, 2011 and 2016 census data. note: each tick mark on the perimeter of the circle is used to represent a total of 200 migrants. figure 1: the internal migration of the mainland china-born population between australian capital cities over three census periods australian population studies 2017 | volume 1 | issue 1 | pages 69–72 © lieske 2017. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org urban, suburban and rural household density trends scott n. lieske* the university of queensland *corresponding author. scott n. lieske. email: scott.lieske@uq.edu.au. address: school of earth and environmental sciences, the university of queensland, brisbane qld 4072, australia paper received 17 september 2017; accepted 23 october 2017; published 20 november 2017 census data may be used to illuminate changing patterns in urban and regional australia, to inform policy development and to help us to better understand our surroundings. when visualised, census data can provide a straightforward means for planners and decision-makers both to identify spatial and temporal patterns and to consider the implications of those patterns for the future (coffee, lange and baker 2016). the visual presentation of census data can also allow citizens to better interpret their lived experience in australia’s capital cities and suburbs. this demographic examines change over time in numbers of households and household density for the entirety of australia. dwelling density is used rather than population density as the former shows not just where we are growing, but how we are growing. an investigation into household locations reveals trends in the preferred built forms of australian life. the methods used in this analysis for understanding changes in household density are based on kolko (2015a, 2015b and 2016), who presents a method for analysing the share of households that live in census geographies with different densities. kolko’s density classifications were developed via an online survey in the united states that asked people to describe where they lived within the constructs of ‘rural’, ‘suburban’ or ‘urban’. analysis of the survey results found the best predictor of how people describe where they live is household density. kolko (2016) used these survey results to collapse households in the united states (us) into eight density categories. converted from households per square mile to households per square kilometre (km), these eight categories are: 0–40; 41–193; 194–386; 387–578; 579–854; 855–1,930; 1,931–3,861; and 3,862+ households per square km. the low end of these density categories are largely congruent with the rural living and rural fringe rural residential development densities found in australia. in planning australia: an overview of urban and regional planning, sinclair and bunker (2007) characterise household densities in the range of 100 to 250 households per square km, the lower two suburban categories presented here, as rural fringe development. they characterise household densities in the range of 1 to 100 households per square km as rural living, a notion congruent with the rural and low-density suburban household densities presented in this study. extending kolko’s approach to the australian context, using data from the australian bureau of statistics (abs) census of population and housing for 2001, 2006, 2011 and 2016, household counts by australian statistical geography standard statistical area 2 (sa2) are presented in figure 1. d e m o g ra p h ic http://www.australianpopulationstudies.org/ mailto:scott.lieske@uq.edu.au 70 lieske s australian population studies 1 (1) 2017 figure 1: density of australian households by sa2 area, 2001–2016 source: calculated from abs 2001, 2006, 2011 and 2016 census data. these results show a broad pattern of growth across all rural, suburban and urban density categories in australia. the only exception is the second highest suburban density category, which shows a decrease in households from 2001–2006. these results suggest the variety of residential choices from rural to high density urban each hold appeal to various segments of australia’s growing population. insight may also be gained by considering the spatial pattern of these results. mcguirk and argent (2011) noted that urban expansion, peri-urban growth and population increases above the national average were occurring in australia’s four mega-metropolitan areas: geelong–melbourne– mornington peninsula in victoria; sunshine coast–brisbane–gold coast in south-east queensland; newcastle–sydney–wollongong in new south wales; and wanneroo–perth–mandurah in western australia. taking advantage of the consistent spatial units for the 2006, 2011 and 2016 censuses available in the abs 2016 time series profile (abs 2017), we can illustrate how the changes described by mcguirk and argent (2011) can occur over a relatively short period of time. figure 2 presents the household densities shown in figure 1 for two time periods, 2006 and 2016, combined into just three categories: rural (0–40 households per square km); suburban (41–854 households per square km); and urban (855+ households per square km). results are presented for two of australia’s mega-metropolitan areas: geelong–melbourne–mornington peninsula in victoria; and sunshine coast–brisbane–gold coast in south-east queensland. 0 200,000 400,000 600,000 800,000 1,000,000 1,200,000 1,400,000 1,600,000 1,800,000 2,000,000 0 -4 0 r u ra l 4 1 -1 9 3 s u b u rb an 1 9 4 -3 8 6 s u b u rb an 3 8 7 -5 7 8 s u b u rb an 5 7 9 -8 5 4 s u b u rb an 8 5 5 -1 9 3 0 u rb an 1 9 3 1 -3 8 6 1 u rb an 3 8 6 2 + u rb an n u m b er o f h o u se h o ld s household density category (households per km2) 2001 2006 2011 2016 australian population studies 1 (1) 2017 lieske s 71 figure 2: neighbourhood density categories of australian households 2006 and 2016 in the mega-metro regions of geelong–melbourne–mornington peninsula and sunshine coast–brisbane–gold coast the mapped results in figure 2 support coffee, lange and baker (2016), who found that populations were increasing beyond the middle-ring suburbs of cities and towards the outlying suburban fringe. the results are congruent also with spencer, gill and schmahmann (2015, p. 1), who observed that a ‘significant proportion’ of the population of australia’s three largest cities live at low suburban densities. they further observed: ‘australia’s reputation as … highly urbanised perhaps belies the predominance of low density development across australia’s metropolitan areas. australian cities … feature pockets of high density among a background of low density’ (spencer, gill and schmahmann 2015, p. 1). abs 2016 census data show that while urban areas are expanding rapidly in terms of population and households, suburban areas are expanding rapidly in terms of space. it appears australia is rapidly becoming a suburban nation. there is a continuing need to develop and refine our understanding of the processes, drivers and consequences of urban growth and expansion. suburbanisation in australia and other changes in household density can be linked with population growth and other demographic trends such as movement of particular age cohorts, patterns of socioeconomic advantage and disadvantage, the location of housing and employment and lags in middle and outer ring infrastructure provision (o’neill 2010; mcguirk and argent 2011). they are associated also with impacts on environmental quality, agricultural production, climate change vulnerability and resilience. the results presented in this paper also raise the issue of mega-city governance put forward by steele et al. (2011). further, the considerable expansion of suburban development between 2006 and 2016 combined with decreasing housing affordability over the same time period suggests that the issue of housing affordability will not be solved by supply alone. 72 lieske s australian population studies 1 (1) 2017 references australian bureau of statistics (abs) (2017) 2003.0 – census of population and housing: time series profile, australia, 2016, viewed 21 july 2017, http://www.abs.gov.au/ausstats/abs@.nsf/mf/2003.0?opendocument. coffee n t, lange j, baker e (2016) visualising 30 years of population density change in australia’s major capital cities. australian geographer 47(4): 511–525. doi: 10.1080/00049182.2016.1220901. kolko j (2015a) data and methodological details, viewed 4 may 2016, http://jedkolko.com/wpcontent/uploads/2015/05/data-and-methodological-details-052715.pdf. kolko j (2015b) how suburban are big american cities?, viewed 4 may 2016, http://fivethirtyeight.com/features/how-suburban-are-big-american-cities/. kolko j (2016) urban revival? neighborhood data show that u.s. suburbanization continues (wonkish), viewed 4 may 2016, http://jedkolko.com/2016/03/25/neighborhood-data-show-that-u-ssuburbanization-continues/. mcguirk p and argent n (2011) population growth and change: implications for australia’s cities and regions. geographical research 49(3): 317–335. o’neill p m (2010) infrastructure financing and operation in the contemporary city. geographical research 48 (1): 3–12. doi: 10.1111/j.1745-5871.2009.00606.x sinclair i and bunker r (2007) planning for rural landscapes. in: thompson s (ed.) planning australia: an overview of urban and regional planning. port melbourne vic.: cambridge university press; 159– 177. spencer a, gill j and schmahmann l (2015) urban or suburban? examining the density of australian cities in a global context. paper presented at the state of australian cities national conference, gold coast, queensland, 9–11 december 2015. steele w, crick f, serrao-neumann s, sharma v and wadsworth j (2011) governing the australian megalopolis: the challenge of the 200km city (and beyond). paper presented at the state of australian cities national conference proceedings. melbourne, victoria, 29 november–2 december 2011, viewed 4 may 2016, http://soac.fbe.unsw.edu.au/2011/papers/soac2011_0030_final(1).pdf. http://www.abs.gov.au/ausstats/abs@.nsf/mf/2003.0?opendocument http://jedkolko.com/wp-content/uploads/2015/05/data-and-methodological-details-052715.pdf http://jedkolko.com/wp-content/uploads/2015/05/data-and-methodological-details-052715.pdf http://fivethirtyeight.com/features/how-suburban-are-big-american-cities/ http://jedkolko.com/2016/03/25/neighborhood-data-show-that-u-s-suburbanization-continues/ http://jedkolko.com/2016/03/25/neighborhood-data-show-that-u-s-suburbanization-continues/ http://soac.fbe.unsw.edu.au/2011/papers/soac2011_0030_final(1).pdf australian population studies 2018 | volume 2 | issue 2 | pages 3-11 © mcdonald 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org commentary australia should continue its current comprehensive population policy – at least for the next decade peter mcdonald* the university of melbourne * corresponding author. email: mcdonald.p@unimelb.edu.au. address: melbourne school of population and global health, university of melbourne, vic 3010, australia paper received 15 august 2018; accepted 27 october 2018; published 12 november 2018 1. introduction the most recent official statement on a population policy for australia concluded: it is more useful for governments, businesses and communities to focus on ways of improving our wellbeing, protecting our environment and making better use of the resources we have, rather than trying to determine an absolute limit to our population and focussing efforts on restricting growth in order to not exceed this ‘limit’ (department of sustainability, environment, water, population and communities 2011: 25). in other words, australian population policy does not take the form of specification of a target population level or even a target rate of population growth. australia is not alone in this regard. while countries may have policies to increase or decrease the rate of population growth, usually because their fertility rate is regarded as too high or too low, no country in the world is aiming for a specific population number or a specific rate of population growth. does the absence of precise targets for total population and for the rate of population growth mean that australia does not have a population policy? that seems to be the popular perception based on the current debate about population, and no less an authority than the productivity commission has recently called for a population policy for australia. the commission gave its view on what such a population policy should do: the primary objective of immigration and the government’s population policy is to maximise the economic, social and environmental wellbeing of the australian community (existing australian citizens and permanent residents and their future offspring) (productivity commission 2016: 108). the first problem with this definition is that maximising the economic, social and environmental wellbeing of the australian community is the raison d’etre of all policy, including tax policy, industry policy, energy policy and education policy and, indeed, of government itself. the second problem is http://www.australianpopulationstudies.org/ mailto:mcdonald.p@unimelb.edu.au 4 mcdonald australian population studies 2 (2) 2018 that accurate modelling of all these outcomes at some undefined time in the future is impossible – that is why it hasn’t been done. the third problem is that this statement provides no concern for the wellbeing of australians and their children who arrive from the day after the modelling is done. to be practical, population policy must have more modest objectives. taking a more pragmatic approach, i argue that australia already has a sophisticated, multi-faceted and effective population policy that has five components: maximising survival; supporting families to have the number of children that they want; moderating the speed and extent of population ageing; providing the skills that australia needs to promote its economic development; and influencing population distribution. 2. maximising survival australia aims to keep its population healthy and living long lives. this policy has been particularly successful from the 1970s onwards. death rates below the age of 75 years are now so low that, for women, their total elimination would add only two years to the expectation of life of australian women. just as spectacularly, death rates for older australians have plummeted since 1970. mortality in 1970-72 was such that 54 percent of men reaching the age of 55 were dead by age 75. by 2014-16, this percentage had fallen to 20 per cent (mcdonald 2017a). this has come about through the promotion of healthier lifestyles and safer environments but also by greatly increased public expenditure on health. the national transfer accounts for australia show that, between 1981-82 and 2009-10, real per capita health expenditure on persons aged 75 years and over in australia increased by a factor of 6.4 times. as the australia population aged 75 years and over increased three times in the same period, aggregate real public expenditure on the health of persons aged 75 years and over increased by an amazing 19 times (mcdonald 2017b). australia has been able to achieve this result without undue fiscal strain because government revenue increased during this period as a result of sustained economic growth. while the policy of maximising survival leads to a larger population particularly at older ages, there are no calls to reverse the trend. 3. supporting families to have the number of children that they want today, many countries in the world express concern about the level of their fertility rate. almost all countries with a fertility rate of 4.0 births per woman or more want to reduce the rate while almost all countries with a fertility rate below 1.5 births per woman want to increase their fertility rate (unfpa 2018). most countries would like to see their fertility rate fall in the relatively narrow range of 1.5 to 2.5 births per woman. this is very sensible because sustained high fertility leads to very rapid population growth which impedes economic and social development while sustained very low fertility leads to rapid population decline and excessive population ageing (unfpa 2018). planning to keep the fertility rate within this relatively narrow band is good policy (mcdonald 2006). in the case of australia, the fertility rate has fluctuated between 1.7 and 2.0 births per woman – an ideal range – for the past 42 years. this excellent result did not just happen. its achievement has been supported by the provision to women and men at low cost of the means to control the number of children that they have, that is, access to contraception and abortion. while there remains room for improvement, australian governments have also implemented a range of policies to support families with children such as subsidised childcare, parental leave, social security payments related to australian population studies 2 (2) 2018 mcdonald 5 children, and public support for education. while paul ehrlich (bateman 2016) and sustainable population australia (white 2009) have called for a china-style, one-child policy for australia, all governments, now including china, think that a one-child policy is not a great idea, leaving aside the human rights implications. fortunately, there is strong political support in australia for policies that support families to have the number of children that they want. 4. moderating the speed and extent of population ageing in the absence of migration, reduction of mortality and a fertility rate below the replacement level of around 2.06 births per woman leads inevitably to population ageing and population decline. at 30 june 2017, 15.4 per cent of the australian population was aged 65 years and over. if net overseas migration (nom) was fixed at zero, this would rise to 26.8 per cent by 2051, a rise of 11.4 percentage points. with the level of nom of 200,000 per annum continuing until 2051, 20.5 per cent of the population would be aged 65 years and over in 2050, a rise of 5.1 percentage points1. thus, while sustained migration at the present level will not stop the population from ageing, when compared with zero migration, it reduces population ageing very substantially. put another way, with nom of 200,000 per annum between now and 2051, the number of people aged 65 and over would be only 427,000 more than if nom was zero in the same period. that is, between now and 2015, the level of nom makes almost no difference to the number of older people in 2051. in contrast, with nom of 200,000 per annum, the number of people in the working ages of 20-64 years would be 6.8 million higher than if nom was zero. those additional 6.8 million people in the working ages will make a huge difference to the standard of living of older people in 2051. nom modifies population ageing because migrants are, on average, considerably younger than the australian population but, more significantly, because migrants, before they themselves become old, will have had their children and their grandchildren. nom of 200,000 per annum from today onwards would make almost no difference to the number of deaths in australia over the next 40 years but a very large difference to the number of births. this is not because migrants have a higher birth rate than non-migrants per woman but because migrants add to the population of childbearing age. if fertility remains at 1.8 births per woman, with zero nom, the australian population would begin to fall around 2045. the question then becomes: what level of nom produces the best outcomes in relation to population ageing? to address this question, in may 2010, at the request of the department of immigration and citizenship, mcdonald and temple (2010) conducted a study to identify if there was an ‘optimal’ range for nom where the criterion for an ‘optimum’ was the impact of immigration on population ageing and, hence, upon the growth rate of gdp per capita. they concluded that this range was 165,000 to 210,000. in 2011-12, the gillard labor government set the migration planning level in the middle of this range at 185,000. a later study by the same authors set this range at 160,000 to 220,000 (mcdonald and temple 2014) and, from 2012-13 until now, the planning level has been set in the middle of this range at 190,000 making for a run of nine years in which the 1 the projections results in this section are based on the june 2016 estimated resident population and assume that fertility is constant at 1.8 births per woman and that expectation of life rises by 2015 to 85.6 years for men and 88.3 years for women 6 mcdonald australian population studies 2 (2) 2018 migration planning level has been near-constant. the study showed that between 2013 and 2053, gdp per capita would be 12 per cent higher in real terms with nom at 180,000 than it would be if nom was zero across these years. for perspective, 12 per cent is larger than the overall increase in gdp per capita in australia over the past decade. an important consideration in this modelling is that nom is not the same entity as the migration planning level. the annual planning level simply consists of the total number of people to be accepted as new permanent residents in the skilled and family streams. in addition, for many years, the australian government has set the annual permanent humanitarian intake at about 13,0002. in contrast, nom is the net outcome of numerous forms of temporary and permanent movement into and out of australia as shown in table 1. table 1: components of net overseas migration by visa/movement type, australia, 2004-05 to 2015-16 (12year aggregate) visa/movement type visa components of net overseas migration, 2004-05 to 2015-16 arrivals departures net (number) net (%) permanent 1,085,468 220,812 864,656 34.0 skilled 503,424 92,815 410,609 16.2 family 398,153 62,543 335,610 13.2 humanitarian 130,453 1,665 128,788 5.1 other 53,457 63,808 -10,351 -0.4 temporary 2,733,004 1,187,117 1,545,887 60.8 skilled 416,795 170,739 246,056 9.7 student 1,239,551 447,445 792,106 31.2 working holiday 461,312 179,371 281,941 11.1 visitor 529,629 185,910 343,719 13.5 other 85,707 203,650 -117,943 -4.6 new zealand citizens 529,722 232,060 297,662 11.7 australian citizen 904,020 1,079,413 -175,393 -6.9 other 162,600 154,269 8,331 0.3 total 5,414,814 2,873,671 2,541,143 100.0 source: australian bureau of statistics, migration, australia, 2016-17. abs catalogue no. 3412.0. notes: numbers do not add precisely due to abs randomisation process. persons may change their visa type between arrival and departure, thus affecting the net figure for any visa/movement type. for example, the relatively large negative figure for ‘other temporary’ mainly reflects people who left australia when they were on a bridging visa although they had arrived on some other temporary visa. if the measured impact of migration on gdp per capita is based on the impact of nom, how can this be reconciled with the setting of the annual permanent migration intake? the answer is that, although nom fluctuates from year to year because of surges in temporary arrivals or departures, in 2 the humanitarian program is temporarily at a higher level due to a special allocation of places to syrian refugees australian population studies 2 (2) 2018 mcdonald 7 the longer term, temporary migrants can only remain in australia if they are granted permanent residence through the permanent migration program. as the net impact of the combined movements of australian and new zealand citizens is relatively small (less than 5% of nom from 2004-05 to 2015-16, see table 1), in the long run, nom and the migration planning levels are very similar (see figure 1). nevertheless, temporary migration serves the very important purpose of providing a ready pool from which the majority of permanent residents are selected. over the past decade, by far the largest category of temporary residents has been international students and table 1 shows that this category has made the largest contribution to nom. in sum, the level of nom that has resulted from the government’s migration planning levels over the past nine years, if sustained into the future, would have a highly beneficial impact on population ageing and hence on the level of gdp per capita in australia in the years to 2051. by 2051, australia would be among the youngest countries in the oecd. the offsetting factor is that, with nom of 200,000 per annum, the total population rises by 2051 to 36 million compared with 26 million (and falling) if nom was zero – but 70 per cent of the additional 10 million people will be in the productive working ages. the implications of an additional 10 million people are considered below. figure 1: annual net overseas migration (nom) compared with the annual grants of permanent residence through the permanent migration program including humanitarian, australia, 1983-84 to 2016-17 sources: department of home affairs; australian bureau of statistics. 5. providing the skills that australia needs to promote its economic development while the total numbers in the annual migration program may be set primarily on the basis of the impact of migration on population ageing and, hence upon gdp per capita, the composition of the skilled stream is determined by perceived skill shortages in the australian labour force that cannot be met by the existing population. the skilled migration program is restricted to managers, 8 mcdonald australian population studies 2 (2) 2018 professionals, para-professionals and skilled tradespeople to ensure that immigrant workers are persons with high labour productivity. within these skill categories, the government identifies those occupations where domestic supply falls short of domestic demand and includes these occupations on the list of occupations eligible for skilled migration. a wider list of occupations is applied where the applicant is nominated by an employer or by a state or territory government. the evidence is strong that the size and composition of australia’s migration program in recent times has been associated with strong labour demand across those years. between june 2011 and june 2016, total employment in australia grew by 739,000 people. this increase was composed of 613,000 migrants who entered australia after june 2011, 278,000 additional workers over the age of 55 years who were present in australia in june 2011 and a net fall of 152,000 among people aged under 55 who were present in australia in june 2011 (mcdonald 2017c). at the same time, the unemployment rate in september 2018 was at its lowest point since april 2012. since 2011, the large immigration intake has been effectively absorbed into the australian labour force. this could not have happened if there had not been an equivalent level of labour demand. looking to the next decade, australia is facing a labour supply crunch as large numbers of babyboomers retire at the same time as the young cohorts entering the labour force ages are smaller in number than their predecessors. with zero nom from 2016 to 2026, the age group 20-34 would fall by 725,000; with nom at 70,000 it would fall by 36 thousand; and with nom at 200,000, it would rise by 413 thousand. at the same time, the population in the retirement ages would increase under all scenarios by about 1.35 million. the latest abs job vacancies data (abs 2018) show a continual rise in job vacancies from 2014 onwards, and vacancies are rising at the rate of 19.3 per cent per annum. australia has created an immigration system that is responsive to labour demand. this is nowhere more evident than in the recent trends in nom at the state and territory level. when the mining boom was at its peak, nom was historically high for the boom states of western australia and queensland. nom dropped off sharply to these states when the mining boom ended. now, nom is directed towards the boom cities of sydney and melbourne. this reflects shifts in the direction of investment by firms and a corresponding shift in labour demand. all the indications are that the number of job openings in australia over the next six years will be very high, that is, labour demand will remain very strong. using econometric modelling, shah and dixon (2018: table 4) have estimated that there will be 4.14 million job openings in australia across the eight years 2017-2024. more than half of these openings (2.27 million) represent replacement demand driven almost exclusively by retirement of the baby-boom generation. some of these openings will be filled by the next generation of young australian workers, but migration at least at the current level will be required to meet this demand. shah and dixon (2018: appendix table a1) also estimate that there will be very considerable change in the distribution of occupations over the period 2016 to 2024. this once more emphasises the need for young workers because it is much easier for younger workers, especially those who have not yet entered the labour force, to adjust to changes in demand for particular occupations. with zero nom, the number of employed 15-34 years-olds would fall by 518 thousand from 2016 to 2026 (assuming australian population studies 2 (2) 2018 mcdonald 9 constant employment participation rates); with nom continuing at 200,000, their number would increase by 425 thousand, a turnaround of close to a million young workers. thus, migration greatly enhances the capacity for the occupational composition of australia employment to respond to demand. 6. population distribution, cities and regions in australia, residents are free to move and take up residence in another location. this means that the population distribution will reflect the preferences that they make. in recent times, residents, old and new, have displayed a distinct preference to live in the major cities of sydney, melbourne and brisbane and in their satellite towns and cities. in 2016-17, 77 per cent of australia’s total population growth was in sydney, melbourne, brisbane and their satellites (newcastle, wollongong, central coast, geelong, melton, bendigo, ballarat, gold coast, sunshine coast and toowoomba). while melbourne’s population grew by more than 2,000 per week, the combined growth of the two fastest growing inland country towns (dubbo and albury-wodonga) was just 2,000 a year. as the global economy moves towards mega cities, there should not be an expectation that future growth of the australian population, in the foreseeable future, can be redirected in anything other than a minor way to regional australia. such redirection is important in keeping regional australia viable but, while the australian economy remains strong, labour demand will be strongest in sydney, melbourne, brisbane and their satellites. accordingly, most of the growth of population will be in these cities. this has been recognised appropriately in the emphasis placed by the federal and state and territory governments upon investment in city infrastructure. it should also be remembered that, in general, the provision of urban infrastructure has lagged behind population growth in australian cities. if you want the evidence, view the sombre (but highly entertaining) you tube video on the 1954 plan for melbourne (https://www.youtube.com/watch?v=mrmovhij34m). some have suggested that lowering the level of the migration program would provide a ‘breathing space’ so that infrastructure development could catch up with population growth. this is flawed logic because if, as argued above, labour demand remains very strong at least in the large cities, firms unable to fill that demand from international migration will draw instead upon the rest of australia and on new zealand. wages and opportunities will be higher in sydney and melbourne and the best talent from the rest of australia will be drawn to these cities. the infrastructure problem in the big cities would not have gone away and regional australia will lose population. and major construction of infrastructure in the big cities requires labour just as mine construction phase did in western australia and queensland during the mining boom. both labor and coalition governments over the past decade have sought to ensure that economic growth remains strong. a wealthy australia will be in a strong position to fund the services required by the growing population, to invest in new urban infrastructure and renewable energy sources, and to deal with environmental issues. in the coming years of the labour supply crunch, present australian population policy is in keeping with these objectives and should be continued at least until 2026. https://www.youtube.com/watch?v=mrmovhij34m 10 mcdonald australian population studies 2 (2) 2018 7. key messages • australia has an effective population policy – and should stick with it at least to 2026. • australia is facing a labour supply crunch in the next decade as the baby-boom retires and because the future cohorts entering the labour force at young ages are much smaller than the current young working population. • labour demand is very strong and the growth in job vacancies is approaching 20% per annum. • the occupational structure of the labour force is set to change considerably. young workers are more easily able to adapt to these changes than are older workers. • at present labour demand is strongest in the big cities. if this demand is not met by immigrants, it will be met by people moving from the rest of australia and from new zealand. • the big cities will continue to grow. there is no substitute for investment in urban infrastructure. references australian bureau of statistics (2018) job vacancies. catalogue no. 6354.0. canberra: abs. bateman d (2016) scientist calls for a one-child policy to curb population explosion. the cairns post 11 november 2016. https://www.heraldsun.com.au/news/national/scientist-calls-for-onechildpolicy-to-curb-population-explosion/news-story/6ac63d6ee1d3fff4b98a26ad5b17cabe department of sustainability, environment, water, population and communities (2011) sustainable australia – sustainable communities: a sustainable population strategy for australia. canberra: commonwealth of australia. http://apo.org.au/system/files/166281/apo-nid166281-770266.pdf mcdonald p (2006) ‘low fertility and the state: the efficacy of policy’. population and development review 32(3): 485-510. mcdonald p and temple j (2010) immigration, labour supply and per capita gross domestic product: australia 2010-2050. canberra: department of immigration and citizenship. https://www.homeaffairs.gov.au/reportsandpublications/documents/research/labour-supplygdp-2010-2050.pdf#search=peter%20mcdonald mcdonald p and temple j (2014) the long term effects of ageing and immigration upon labour supply and per capita gross domestic product: australia 2012-2062. canberra: department of immigration and border control. http://www.immi.gov.au/search/pages/results.aspx?k=the%20long%20term%20effects%20of% 20ageing%20and%20immigration%20upon%20labour%20supply%20and%20per%20capita%20g ross%20domestic%20product mcdonald p (2017a) long-term changes in mortality by age and sex in australia. powerpoint presentation to a symposium organised by the arc centre of excellence in population ageing research, melbourne town hall, 14 august 2017. mcdonald p (2017b) ageing in australia: the impact of immigration. powerpoint presentation to a seminar organised by the australian and new zealand school of government, melbourne business school, 28 november 2017. mcdonald p (2017c) international migration and employment growth in australia, 2011-2016. australian population studies 1 (1): 3-12. productivity commission (2016) migrant intake into australia. productivity commission inquiry report, 13 april 2016. shah c and dixon j (2018) future job openings for new entrants by industry and occupation. adelaide: commonwealth of australia, ncver. https://www.heraldsun.com.au/news/national/scientist-calls-for-onechild-policy-to-curb-population-explosion/news-story/6ac63d6ee1d3fff4b98a26ad5b17cabe https://www.heraldsun.com.au/news/national/scientist-calls-for-onechild-policy-to-curb-population-explosion/news-story/6ac63d6ee1d3fff4b98a26ad5b17cabe http://apo.org.au/system/files/166281/apo-nid166281-770266.pdf https://www.homeaffairs.gov.au/reportsandpublications/documents/research/labour-supply-gdp-2010-2050.pdf#search=peter%20mcdonald https://www.homeaffairs.gov.au/reportsandpublications/documents/research/labour-supply-gdp-2010-2050.pdf#search=peter%20mcdonald http://www.immi.gov.au/search/pages/results.aspx?k=the%20long%20term%20effects%20of%20ageing%20and%20immigration%20upon%20labour%20supply%20and%20per%20capita%20gross%20domestic%20product http://www.immi.gov.au/search/pages/results.aspx?k=the%20long%20term%20effects%20of%20ageing%20and%20immigration%20upon%20labour%20supply%20and%20per%20capita%20gross%20domestic%20product http://www.immi.gov.au/search/pages/results.aspx?k=the%20long%20term%20effects%20of%20ageing%20and%20immigration%20upon%20labour%20supply%20and%20per%20capita%20gross%20domestic%20product australian population studies 2 (2) 2018 mcdonald 11 unfpa (united nations population fund) (2018) state of world population 2018: the power of choice, reproductive rights and the demographic transition. new york: unfpa. white h (2009) institute one child policy for a “sustainable” australia: population control group lifesitenews.com, 24 april 2009. https://www.lifesitenews.com/news/institute-one-child-policyfor-a-sustainable-australia-population-control-g https://www.lifesitenews.com/news/institute-one-child-policy-for-a-sustainable-australia-population-control-g https://www.lifesitenews.com/news/institute-one-child-policy-for-a-sustainable-australia-population-control-g 7. key messages references australian population studies 2017 | volume 1 | issue 1 | pages 13–25 © wilson and taylor 2017. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org alternative methods of determining the number of house of representatives seats for australia’s territories tom wilson* charles darwin university andrew taylor charles darwin university *corresponding author. email: tom.wilson@cdu.edu.au. address: northern institute, charles darwin university, darwin nt 0909, australia paper received 15 august 2017; accepted 19 october 2017; published 20 november 2017 abstract background population size determines the number of seats each australian state and territory is entitled to in the house of representatives. the northern territory (nt) and australian capital territory (act) were allocated two and three seats, respectively, in the august 2017 determination, but by very small margins. both territories risk losing a seat at the next determination. this would result in them having considerably more people per member of parliament than any of the states. aims this paper (1) provides modelling to support the consideration of alternative rules for determining membership entitlement to the house of representatives which does not disadvantage the nt and act and (2) presents population projections for future determinations under the current and alternative rules. data and methods population projections for the states and territories were produced for three demographic scenarios. the resulting numbers of seats for the nt and act were calculated for each scenario under the current and proposed alternative seat entitlement rules. results under the existing rules the nt and act would only keep their current number of seats at the next determination if they experienced higher net in-migration than in recent years. under the alternative seat entitlement rules suggested, the nt and act would be very unlikely to lose any seats and would almost certainly gain seats in ensuing decades. conclusions there is a case for re-examining the way the states and territories are allocated seats in the house of representatives. key words commonwealth electoral act; constitution; house of representatives; australia; seat entitlements; population projections; northern territory; australian capital territory. http://www.australianpopulationstudies.org/ mailto:tom.wilson@cdu.edu.au 14 wilson t and taylor a australian population studies 1 (1) 2017 1. introduction population statistics play a central role in determining the number of seats in the house of representatives assigned to each state and territory. the seat allocation process is set out in the commonwealth electoral act 1918, and is based on the fundamental principle described in the australian constitution that each state is allocated a share of seats equal to its share of the national population (commonwealth electoral act 1918; commonwealth of australia constitution act 1900). various special provisions, along with the need to round fractional seat entitlements (e.g. 10.6 or 11.4 seats) to the nearest whole number, mean that the population–seat relationship is imprecise, but much of the basic principle is retained. because of changes to state and territory shares of the national population over time, the electoral act requires the australian electoral commissioner to periodically re-calculate seat entitlements. a year-and-a-day after the first sitting of the house of representatives following a general election, updated population numbers are obtained from the australian bureau of statistics (abs). new calculations of state and territory seat entitlements are then made. when the number of seats in a state or territory changes, a redistribution of electoral boundaries within that jurisdiction is initiated and the new boundaries come into effect at the next federal general election. sometimes seat entitlement calculations have generated controversy, especially in the case of the northern territory (nt). in the 2003 determination of state and territory entitlements for the house of representatives, the nt saw its entitlement reduced from two seats to just one because of a falling share of the national population (australian electoral commission 2003). but it was very close: if the nt had just 295 more people it would have retained two seats. the ensuing controversy resulted in an inquiry into representation of the territories in the house of representatives by the joint standing committee on electoral matters. the committee report recognised the greater uncertainty of territory estimated resident population (erp) calculations relative to those of the states and recommended both that the 2003 seat determination for the nt be set aside and a margin of error be incorporated in future seat determinations ‘when a territory falls short of quota’ (joint standing committee on electoral matters 2003, pp. viii–ix). the electoral act was amended the following year to incorporate the report’s recommendations and the nt retained its two seats. in the years 2013–2016 the nt again experienced population growth below the national rate (wilson 2017a) resulting in a declining share of the national population. in the recent 2017 determination the nt retained two seats, though by a very small margin (australian electoral commission 2017). if the nt were to lose a seat in the near future, about a quarter of a million people would be represented by a single member of parliament, a population to seat ratio much higher than for any of the states. the 2017 determination also gave the act an additional seat, but by a very small margin. if the act were to lose a seat, it too would be subject to a much higher population to seat ratio than any of the states. this raises two key questions: (1) might the nt and act lose a seat in the next determination?; (2) what could be changed to ensure the territories do not lose a seat in the future? this paper proposes two alternative models for seat entitlement rules and presents population and associated seat projections for the nt and act under the current and proposed alternative seat entitlement rules. section 2 of the paper describes the process for calculating seat entitlements prescribed by current legislation, and models two alternative schemes in which the territories are not australian population studies 1 (1) 2017 wilson t and taylor a 15 subject to inferior representation in the house of representatives. population projections based on various scenarios for the three schemes (current and alternative models) are presented in section 3, while brief conclusions form the final section of the paper. 2. current and alternative seat entitlement calculations 2.1 current scheme the current method for seat entitlement calculations is specified in the commonwealth electoral act 1918 as amended and in force on 21 october 2016. the 2016 amendments mean that the calculations differ slightly from those described earlier by abs (2005), corr (2016), payer and taylor (2015) and wilson, beneforti and barnes (2005). the key elements of the process are summarised in the flow diagram in figure 1. seat entitlement calculations for each of the states are relatively straightforward. first, the quota is calculated. the quota is the population required for a jurisdiction to be assigned a seat in the house of representatives. it is defined in the electoral act as the latest official population number for the six states combined, divided by twice the total number of senators for the six states (2 × 72 = 144). the number of senators is defined by legislation. while it can change in theory, for practical purposes the number can be assumed to be fixed at 72. the latest erp of each state is divided by the quota to obtain the seat entitlement, shown in figure 1 as w.f. where w represents the whole number part of the seat entitlement and f the fractional part. the seat entitlement is rounded down if the fractional part f is less than or equal to 0.5, and rounded up if greater than 0.5. if any state (but not territory) has fewer than five seats, then the australian constitution requires the number of seats to be increased to five. in practice this now only applies to tasmania (though long ago it was relevant also to other states). the calculations are more complicated for the nt and act. the populations of the territories of the cocos (keeling) islands and christmas island are included in the nt’s population. (strictly, the electoral act states that if the cocos islands and christmas island do not have sufficient population to be allocated a seat themselves they are to be included with the nt – but in practical terms they can always be regarded as part of the nt.) a similar provision applies to norfolk island whose erp is included in the act’s population until it is entitled to separate representation1; jervis bay territory is counted as part of the act. the provisional seat entitlements for the nt and act are then calculated by dividing their populations by the quota. at this point the calculations for the territories can deviate from those of the states. if the fractional part f of the unrounded preliminary seat number for the nt or act is less than or equal to 0.5, then a check is made to determine whether the population of the territory is within a specified margin of error. this margin of error allowance was introduced to the electoral act in 2004 on the recommendation of the joint standing committee on electoral matters (2003). 1 this is the first seat determination in which norfolk island’s population (most recently 1,756) has been included as part of the act due to recent changes in norfolk island’s status. however, it did not materially affect the seat determination outcome. 16 wilson t and taylor a australian population studies 1 (1) 2017 figure 1: summary of the current house of representatives seat determination calculations source: based on commonwealth electoral act 1918. notes: w.f. = whole number.fraction; se = standard error. quota = combined erp of the 6 states 2 × total no. of senators of the 6 states no. of seats = state erp = w.f. quota is the fractional part f ≤ 0.5? no. of seats rounded down to w no. of seats rounded up to w+1 is the no. of seats < 5? yes no yes no no. of seats unchanged no. of seats set at 5 nt population = nt erp + christmas island erp + cocos islands erp act population = act erp + jervis bay erp + norfolk island erp no. of seats = territory population = w.f. quota states yes no the population is increased by 2 × se of the net undercount is the fractional part f ≤ 0.5? yes no nt act no. of seats rounded down to w no. of seats rounded up to w+1 yes no is the fractional part f ≤ 0.5 and (quota × n.5 – population) ≤ (2 × se net undercount)? is the no. of seats zero? no. of seats set at 1 no. of seats unchanged no. of seats = augmented population = w.f. quota australian population studies 1 (1) 2017 wilson t and taylor a 17 the increase in population required to obtain an entitlement with exactly a 0.5 fraction is then calculated. for example, if the whole number part of the seat entitlement is 2, then this ‘threshold’ population is 2.5 × quota. if the increase required to reach this threshold population is less than or equal to twice the standard error (se) of the net undercount estimated from the last census, then the official population of the territory is taken to be its original population plus twice the se of the net undercount. the seat entitlement calculation is re-calculated using this augmented population. the same rounding process as for the states is then applied. finally, a check is made to ensure that each territory has a minimum of one seat. table 1 presents key statistics from the 2017 seat determination. the most recent official population numbers at the time of the determination were the 31 december 2016 erps published by the abs in australian demographic statistics on 27 june 2017 (abs 2017). using these data, the quota was calculated as 23,729,561 / 144 = 164,788.6181. three jurisdictions experienced changes in their number of seat entitlements. victoria gained a seat while south australia lost one. the act also gained a seat due to the margin of error allowance for its erp. the preliminary unrounded number of seats for the act was calculated as 2.4793 (column b). because the fractional part f was less than 0.5 it was necessary to determine whether the act’s population was within the permitted margin of error to get above 2.5. twice the se of net undercount from the abs 2016 census for the act was 10,694 (column c), while the additional population required to increase the seat entitlement to 2.5 was 2.5 × 164,788.6181 – 408,562 = 3410 (column d). therefore, the population of the act was increased by twice the se of the undercount to obtain an augmented population (column e) and the entitlement calculation was repeated (column f). table 1: state and territory seat determinations, 2017 jurisdiction population (a) population/ quota (b) 2 × se net undercount (c) w.5 quota – population (d) augmented population (e) aug. popn/ quota (f) seats (g) nsw 7,797,791 47.3200 47 vic. 6,244,227 37.8923 38 qld 4,883,739 29.6364 30 sa 1,716,966 10.4192 10 wa 2,567,788 15.5823 16 tas. 519,050 3.1498 *5 nt 247,512 1.5020 2 act 408,562 2.4793 10,694 3,410 419,256 2.5442 3 total – – – – – – 151 source: based on australian electoral commission (2017). note: *5 seat minimum applied. under the current legislation the nt and act have two and three seats, respectively, by very small margins. if they were to drop to one and two seats, then the population being represented by each member of parliament in the territories would be far higher than that of any of the states. there are a number of alternative ways in which the number of seats could be calculated for the territories which would prevent them from being disadvantaged in this way. we propose two alternative seat entitlement schemes, the special quota scheme and the fixed quota scheme, discussed below. 18 wilson t and taylor a australian population studies 1 (1) 2017 2.2 special quota scheme because the australian constitution provides for a minimum of five seats in any state, tasmania receives two more seats than it would be assigned simply on the basis of its population size. the effective quota for tasmania is therefore substantially lower than the actual quota and in the 2017 determination was 519,050 erp / 5 seats = 103,810. under our proposed special quota scheme the effective tasmanian quota would be applied to the nt and act, the argument being that if a state is entitled to minimum representation due to small population size, then these two territories should be afforded the same treatment. the process for the nt and act might be amended to something like this: • the number of seats which would be allocated to each territory under the regular quota is calculated. • if the minimum 5 seat provision is applied to any state, then the effective quota for that state – which could be termed the special quota – is calculated. if the minimum 5 seat provision applies to more than one state then the lowest effective quota is deemed the special quota (though in practice this is unlikely). • if (i) a territory would be allocated fewer than 5 seats by dividing its population by the quota and (ii) the minimum 5 seat provision is applied to any state, then the seat entitlement for that territory is calculated by dividing its population by the special quota. • the number of seats calculated in this way for any territory is capped at 5. the rounding up or down of fractional parts of the seat entitlement remains the same as in the current process, as does the provision of a margin of error based on the se of the net undercount from the last census. had this alternative system been in place in the 2017 determination, then the outcome would have been as shown in table 2: the nt would have achieved two seats comfortably, while the act would have been allocated four seats. the nt’s entitlement of 2.3843 would not have put it within the margin of error to be rounded up to 3. table 2: 2017 seat determinations for the nt and act under the special quota system territory population population/special quota seats nt 247,512 2.3843 2 act 408,562 3.9357 4 source: authors’ calculations. 2.3 fixed quota scheme another alternative scheme would be to keep the current seat entitlement calculation rules but with one exception: the current method of calculating the quota based on the states’ latest populations would be replaced by a fixed number. this might be, for example, 150,000 people per seat. the argument behind this approach is that each member of the house of representatives can only effectively serve a certain number of constituents. therefore, as australia’s population increases, so will the number of seats in the house of representatives. given the constitutional requirement that the total number of seats for the six states be twice the number of senators, the number of senators australian population studies 1 (1) 2017 wilson t and taylor a 19 would also have to increase. this method also has the advantage of being very simple. the seat entitlements which would have been calculated in the 2017 determination with a quota of 150,000 are shown in table 3. the nt would comfortably have been assigned two seats, while the act would have been allocated three seats. the total number of seats in the house of representatives would be 165 under this scheme. table 3: 2017 seat determinations with a fixed quota of 150,000 jurisdiction population population/quota seats nsw 7,797,791 51.9853 52 vic. 6,244,227 41.6282 42 qld 4,883,739 32.5583 33 sa 1,716,966 11.4464 11 wa 2,567,788 17.1186 17 tas. 519,050 3.4603 *5 nt 247,512 1.6501 2 act 408,562 2.7237 3 total – 165 source: authors’ calculations. note: *5 seat minimum applied. 3. projections how might the nt’s and act’s seat entitlements change in the future under the current legislation and alternative calculation schemes described above? to provide answers, population projections were produced for the states and territories from 2016 to 2051. calculations of seat entitlements for the nt and act were then made for every projection year (2021, 2026, … , 2051) under the current, special quota and fixed quota schemes. 3.1 projection methods, data and scenarios projections were prepared using the regional population projection program (reppp) (wilson 2017b). this excel/vba program incorporates a multi-regional type cohort-component model which outputs projections by sex and five-year age group for every fifth year into the future. most input data were sourced from the abs website, primarily from abs.stat (http://stat.data.abs.gov.au/). these included preliminary rebased 30 june 2016 erps, total fertility rates (tfrs) and age-specific fertility rates, state and territory life expectancies at birth, interstate migration flows, and overseas migration flows. national mortality rate projections were created using ediev’s (2008) extrapolative method based on data extracted from the human mortality database (2017). jurisdiction-specific mortality assumptions were created by scaling national mortality projections according to recent life expectancy at birth values. for all three scenarios the average tfrs of 2011–2016 were assumed to remain constant. the populations of the small territories of christmas island, the cocos islands, jervis bay and norfolk island were assumed to remain constant at their 2016 erps. the ses of net undercount from the 2016 census for the nt and act were also assumed to remain constant. http://stat.data.abs.gov.au/ 20 wilson t and taylor a australian population studies 1 (1) 2017 three scenarios with differing migration assumptions were produced: 1. current trajectory scenario, in which the net interstate migration (nim) values of 2011–2016 for the nt and act were held constant; for the states an annual average of the last 20 years of nim was assumed (but adjusted to ensure nim summed to zero across all jurisdictions). net overseas migration (nom) values from 2011–2016 were held constant for all jurisdictions. projections under this scenario demonstrate the population outcomes if the demographic ‘settings’ of the 2011–2016 period for the nt and act were to remain unchanged. 2. low migration scenario, in which nim and nom for the nt and act were held constant at the 10th percentile of their distributions over the last 20 years. assumptions for the states were the same as in the current trajectory scenario (with adjustments made to obtain zero nim when summed across all jurisdictions). projections from this scenario show the result of long-run highly negative net migration outcomes for the two territories. 3. high migration scenario, in which nim and nom for the nt and act were held constant at the 90th percentile of their past distributions. again, assumptions for the states were the same as in the current trajectory scenario (except for adjusted nim values). this scenario’s projections reveal the outcome of consistently high net migration gains for the two territories. assumptions for the scenarios are given in the appendix (table 4). projections from the three scenarios do not cover the range of all possible demographic outcomes, of course. migration for individual fiveyear projection intervals may fall outside the high–low range, and fertility and mortality are both likely to deviate somewhat from the assumptions used. however, past analyses have shown that migration is the greatest source of uncertainty about future population for both the nt and act (wilson 2012), and the high–low ranges considered here cover a wide range of plausible outcomes for the two territories. 3.2 projection results the projected populations of the nt and act according to the three scenarios are shown in figure 2. given the wide range of historical nim and nom values for these two territories, it is not surprising to see substantially different results from the high migration and low migration assumptions. figure 2: population projections for the nt and act, 2016–2051 source: authors’ projections. note: the act’s current trajectory projection is closer to its high migration projection because nom over 2011–2016 was towards the higher end its distribution for the last 20 years. australian population studies 1 (1) 2017 wilson t and taylor a 21 northern territory australian capital territory figure 3: unrounded seat entitlements for the nt and act, 2016–2051, according to three seat calculation schemes and three demographic scenarios source: authors’ calculations. 22 wilson t and taylor a australian population studies 1 (1) 2017 figure 3 illustrates the unrounded seat entitlements calculated for the nt and act if seat determinations were made on 30 june of the projection years 2021, 2026, … , 2051. the detailed calculations behind these graphs are contained in the excel workbook accompanying this paper. under the current seat entitlement rules, each territory only keeps the number of seats assigned at the 2017 determination under the high migration scenario. this is because population growth amongst the six states results in the quota increasing over time, reaching about 260,000 by 2051. under the current trajectory scenario both territories lose a seat in the 2030s but, as the graphs show, they remain very close to losing a seat for the entire preceding period. if the low migration scenario was to eventuate, both territories would probably lose a seat as early as the next determination. under the special quota scheme, the quota is determined by the size of tasmania’s population. the seat projections are therefore less robust because of uncertainty about the future of tasmania’s population. in our projections tasmania experiences only a modest amount of population growth until the early 2030s (to about 540,000), followed by gradual decline. as a consequence, the special quota never exceeds 108,000. under the ‘worst case’ scenario of low migration the nt increases from two to three seats in the 2040s and the act retains four seats through to 2051. under the high migration scenario both territories increase to five seats: the nt at the end of the projection horizon, and the act early on (noting that the special quota scheme provides a maximum of five seats). even if the slightly more optimistic abs 2012-based series b projections for tasmania were used instead (abs 2013), the ‘worst case’ low migration scenario would keep the nt on two seats, and the act on four throughout the projection horizon. under the fixed quota scheme the seat projections are determined solely by each jurisdiction’s future population. under the low migration scenario, both the nt and act remain on two and three seats, respectively, for the whole projection horizon. under the high migration scenario the nt will have gained one seat and the act two by mid-century. 4. conclusion we believe there is a case to re-examine the legislation on representation in the commonwealth house of representatives, focusing particularly on the nt and act. not only are there precedents for this, with revisions made previously to the legislation, it is also permitted under the constitution. section 122 of the australian constitution states: the parliament may make laws for the government of any territory … and may allow the representation of such territory in either house of the parliament to the extent and on the terms which it thinks fit. under the current electoral act both the nt and act are at risk of losing a seat in the house of representatives if current population trends continue. if this were to occur, then the population represented by each of their members of parliament would be greater than in any of the states. preventing future seat losses in the two territories will require much higher net migration than experienced in recent years (or very low population growth in the six states). the alternative special quota and fixed quota seat entitlement schemes proposed in this paper would prevent the territories australian population studies 1 (1) 2017 wilson t and taylor a 23 from losing seats. even under the low migration scenario, neither the nt nor the act lose seats under these two schemes; under the high migration scenario both will gain seats. the straightforward nature of the fixed quota scheme would potentially make for simpler and clearer legislation. alternatively, the special quota scheme would place the nt and act at least on a par with tasmania, in that they would be subject to the same effective special quota. the two schemes could even be combined using a standard quota of 150,000 together with the special quota applied to the nt and act. of course, there are other seat entitlement schemes which could be considered. one would be to provide a minimum of two seats each for the nt and act, a proposal made to the joint standing committee on electoral matters inquiry in 2003 but not recommended by the committee. alternatively, the two territories could be subject to the same minimum number of seats which apply to the states (5 seats), but that might be seen as being too generous to the nt. with no change to the current rules the nt and act could well lose a seat each – possibly at the next determination. importantly, should the nt be reduced to just one seat it would then be by far the most poorly represented jurisdiction in the house of representatives, with about a quarter of a million people to one member of parliament for an electorate covering 1.4 million square kilometres. on that basis alone, there is sufficient weight to consider alternative approaches, including those proposed here. key messages • there is a case for the parliament of australia to re-examine the way seat entitlements are calculated. • in the recent 2017 determination of house of representatives seats the nt and act were allocated two and three seats, respectively. however, they avoiding being assigned just one and two seats, respectively, by the narrowest of margins. • had the nt and act lost seats at the 2017 determination, the two territories would have had a much larger number of people per elected member than any of the australian states. however, projections in this paper demonstrate that under the current seat entitlement rules, the nt and act are at risk of losing a seat each at the next determination. • this paper proposes two alternative ways in which seat entitlements could be calculated for the nt and act which would prevent them from being disadvantaged. under these proposed schemes, the nt and act would be very unlikely to lose any seats at the next determination and therefore would not be disadvantaged in their representation in respect to the states. acknowledgments the authors are most grateful for helpful advice and comments on an earlier draft by australian electoral commission staff and the anonymous reviewers. all opinions and errors remain our own. 24 wilson t and taylor a australian population studies 1 (1) 2017 references australian bureau of statistics (abs) (2005) information paper: determining seats in the house of representatives – legislative requirements for provision of abs statistics. cat. no. 3107.0.55.002. canberra: abs. australian bureau of statistics (abs) (2013) population projections, australia, 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representatives seats for the northern territory. people and place 13(4): 23–33. http://www.aec.gov.au/media/media-releases/2017/08-31.htm http://www.aec.gov.au/media/media-releases/2017/08-31.htm https://www.legislation.gov.au/details/c2004c00469 https://www.legislation.gov.au/details/c2016c01022 http://www.mortality.org/cgi-bin/hmd/country.php?cntr=aus&level=1 http://www.cdu.edu.au/sites/default/files/research-brief-2015-02.pdf http://dx.doi.org/10.1155/2012/419824 http://www.cdu.edu.au/sites/default/files/the-northern-institute/territory_population_update_27-06-2017.pdf http://www.cdu.edu.au/sites/default/files/the-northern-institute/territory_population_update_27-06-2017.pdf http://www.cdu.edu.au/sites/default/files/the-northern-institute/docs/reppp-model-description-revised2.pdf http://www.cdu.edu.au/sites/default/files/the-northern-institute/docs/reppp-model-description-revised2.pdf australian population studies 1 (1) 2017 wilson t and taylor a 25 appendix table 4: summary of projection assumptions used in the three projection scenarios jurisdiction tfr e0 in 2046–51 (males; females) nim per annum nom per annum current trajectory nsw 1.88 88.0; 89.9 -17,429 66,781 vic. 1.77 88.7; 90.1 2,977 58,514 qld 1.94 87.8; 89.4 19,428 29,881 sa 1.85 87.9; 89.7 -3,089 10,649 wa 1.90 88.1; 90.4 1,582 29,436 tas. 1.97 86.3; 88.0 -763 1,176 nt 2.06 82.8; 83.5 -2,375 2,233 act 1.77 88.9; 90.7 -331 2,354 low migration nsw -16,806 66,781 vic. 3,088 58,514 qld 20,148 29,881 sa as above as above -2,978 10,649 wa 1,641 29,436 tas. -736 1,176 nt -2,795 482 act -1,561 -159 high migration nsw -19,099 66,781 vic. 2,717 58,514 qld 17,730 29,881 sa as above as above -3,385 10,649 wa 1,444 29,436 tas. -836 1,176 nt 728 2,111 act 701 3,090 australian population studies 2018 | volume 2 | issue 2 | pages 12-21 © parr 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org commentary what sort of population policy should australia adopt? suggestions for migration, fertility and population research policy nick parr* macquarie university * corresponding author. email: nick.parr@mq.edu.au. address: centre for workforce futures, faculty of business and economics, macquarie university, nsw 2109, australia. paper received 15 august 2018; accepted 27 october 2018; published 12 november 2018 1. introduction: why have a population policy? the implications of population change are wide-ranging and long-lasting. population growth, geographical distribution and compositional change affect the need for all sorts of goods and services, including housing, transport, childcare, education, health, water and energy; labour supply, income, wealth, tax revenue, and government expenditure; land use, living space, the natural environment and the effects of climate; time use; family life; national culture and identity; inequity and inequality; crime and security; and religion (e.g. argyrous et al. 2017; daley and coates 2018; hugo 2012; infrastructure australia 2018; mcdonald 2011; mcdonald and temple 2010; ong et al. 2017; pew research center 2017; piketty 2014; productivity commission 2015, 2016; treasury and home affairs 2018). the long run effect of immigration on the size and composition of australia’s population is more than just a matter of the initial ‘plus one’ per immigrant; it continues over the lifetimes of the immigrants who remain here, is added to by births to migrant parents in australia, and, over the longer run, will also reflect the survivorship, reproduction and emigration of second and higher order generation descendants (schmertmann 1992). similarly, changes to numbers of children born in any one year will affect subsequent numbers of (potential) parents, and, hence, the sizes of subsequent generations across future time. in view of breadth and duration of its various effects, the potential value of australia implementing (and progressively refining over time) an integrated national policy to direct, anticipate, monitor and respond to population change (i.e. a ‘population policy’) would appear to be considerable. 2. the scope of population policy population policy should be simultaneously broad in its range of considerations and focused in terms of its priorities. the considerations include: • the future prospects and scope for change through policy of international migration, internal movement within australia, fertility, and mortality, and the differing implications of alternative combinations of these variables for the future size and composition of national and subnational http://www.australianpopulationstudies.org/ mailto:nick.parr@mq.edu.au australian population studies 2 (2) 2018 parr 13 populations. trajectories of population change over long periods of time should be considered, and not just projected sizes for one future point in time (as occurred during the ‘big australia’ debate). this is because population change and its consequences vary over time, and because population change over any one time period will have ramifications for subsequent population change (treasury 2015; treasury and home affairs 2018; parr and guest 2014). • the implications, both more immediate and sustained over longer periods of time, of such population outcomes for key non-population outcomes, such as labour force size, participation rates and composition, income levels, housing (numbers, types and affordability), road traffic and congestion, public transport use, educational enrolments, university funding, health care need, water use and environmental degradation. • differences in the implications of population change between different geographical locations and for different population subgroups, especially disadvantaged subgroups. • compassionate and emotional grounds for particular types of immigration (i.e. humanitarian and family). • the implications of australian population change and policy for populations overseas, especially for those that are poor, endangered or persecuted. • the implications of population change for biodiversity and environmental sustainability. • population-related budgetary, planning, social, education, family, regional development, foreign aid, health, environmental and other policies. • time lags, degrees of uncertainty, potential for error, and contingency plans. • gaps in knowledge and understanding in all of the above, and how best to address them through coordinated and funded research and through development of the research community. • ministerial and departmental responsibility for the administration of population policy, and the coordination of policy formulation and implementation between australia’s major jurisdictions. for example, whether there should be a federal minister for population, and, if so, whether the portfolio will include responsibility for immigration policy, and how consultation with state and territory governments will be conducted. • the population-related implications and coherence of policy which is made primarily with considerations other than population to the fore but which also has population-related implications. • how accountability will be ensured. for example, whether political parties will provide clear indications of intended population-related direction before elections, and will adhere to such promises if elected. the rest of this brief article focuses on selected aspects of three key elements of population policy: immigration policy, fertility policy, and research policy. 14 parr australian population studies 2 (2) 2018 3. migration policy by international standards australia’s immigration is highly planned and managed (hugo 2014). current migration policy covers movement on a range of temporary visas (including student, temporary work-related, working holiday maker, and visitor), as well as eligibility for permanent visas (which is almost entirely on the basis of skill, family and humanitarian grounds), and moves in and out of australia by australian and new zealand citizens and some others (hugo 2014a, 2014b; doha 2018). not least because it is the component of population change which is the most readily changed through policy, migration policy, especially policy on the annual numbers of permanent residence visas issued, should be the cornerstone of any australian population policy. the long-run impact on australia’s population of visa grants will reflect the length of stay and longevity of the immigrants, the children they have after moving here, and the reproduction, emigration and life expectancies of their descendants in australia. thus whilst changes to temporary visa entries can have large shorterterm impacts on population, over the long run the numbers of permanent residence visas (including those issued to previous temporary visa holders) will have a much greater bearing on population growth than the number of temporary visas (abs 2018a). migration policy should align with (relatively) acceptable and feasible trajectories for future population change. it should recognise that in the more immediate future some degree of population growth and population ageing is virtually inevitable, both nationally and for australia’s largest cities, avoid zero (or negative) growth or zero ageing ‘population pipedreams’, and consider longer-run sustainability issues, as well as the more immediate implications of population change (abs 2013; martin et al. 2017; parr et al. 2016). there are both advantages and disadvantages to higher levels of immigration. higher levels of immigration, especially suitably-targeted skilled immigration, can help to increase living standards (mcdonald and temple 2010; parr and guest 2014; productivity commission 2016). whilst their perperson economic benefits tend to be smaller than those of skilled migration, there are compelling compassionate and emotional justifications for a humanitarian component and for most of the current components of australia’s family immigration stream (treasury and home affairs 2018). higher immigration and, hence, population growth, particularly in sydney and melbourne, has also been linked to ‘population problems’, including traffic congestion, housing affordability issues, localised school capacity shortage, and concerns related to the spread of higher density housing (daley and coates 2018, infrastructure australia 2018, ong et al. 2017). the economic consequences of a change to immigration numbers will depend on how that change is targeted. substantial proportions of particular occupational workforces (including accountants, and various ict professional and health professional occupations) are the product of australia’s skilled migration program. however, there are also smaller numbers of former skilled migrants working in less-skilled occupations (for example carers and aides, cleaners and laundry workers, numerical clerks, factory process workers and sales assistants and salespersons) which have never been on the lists of eligible occupations for skilled stream visas (albeit somewhat smaller percentages for primary applicants than for secondary applicants) (abs 2018b; birrell 2018; de alwis and parr 2018). it would be preferable for any reduction to the size of the skilled stream to disproportionately reduce the proportion of migrants who do not work in the stream’s eligible occupations post visa award. australian population studies 2 (2) 2018 parr 15 recent improvements in data availability, including linked visa application and census datasets, have strengthened the evidence base for assessment of the labour market outcomes of skilled stream entrants and their variation between demographic groups and geographical areas (abs 2018b). the provision of data at a finer level of detail (especially for the occupations for which the skills assessments were undertaken), facilitation of further data linkage initiatives (for example by recording tax file numbers with other visa data), and empirical analysis of the resulting data may help to inform increases in the efficiency with which skilled stream entrants fill shortages in areas of need and contribute to taxation revenue, and reduction in numbers of skilled migrants not working in skilled migration eligible occupations. the inclusion of a question measuring time-related underemployment on the census could facilitate identification of labour underutilisation at the detailed level of classification of occupations used in skilled migrant selection, and hence inform the targeting of reduction to migrant numbers. as well as its targeting, the timing of changes to total skilled stream visa numbers and the integration of migration policy with education and training policy are also important considerations. education and training is a critically important determinant of labour supply, especially for professional and other high skill occupations, such as those targeted by the skilled migration stream. in order to reduce the risk of oversupply and related graduate and immigrant skills wastage, it is important the setting of quota sizes for the occupations which are targeted by skilled migration is responsive to changes in domestic graduate supply, as well as to demand, productivity and workforce attrition trends in these occupations. however, in view of the inevitable time lags between policy initiation and change to graduate numbers, a phased approach to migrant number reduction, which is harmonised increases in graduate numbers, would be advisable. population policy should incorporate contingency plans for responses to rapid, unanticipated increases in need for critically important occupations with long education and training supply pipelines. flexible plans for increases or decreases in suitably-skilled immigrant numbers in response to sudden changes in demand for mining and other industries which operate in relatively sparsely-populated regions which lack locallyavailable labour and face volatile demand should also be formulated. the recent growth in numbers of ‘domestic’ australian higher education graduates, particularly into occupational workforces which currently rely heavily on skilled immigration, such as health, engineering and related technologies, and information technology, provides reason for reassessment of the related skilled migration occupation quotas (birrell 2018; crettenden et al. 2014; det 2018). proactive, suitably-calibrated, expansion of domestic graduate numbers, such as that recently implemented as a part of workforce planning for doctors and nurses, could potentially reduce risks of future labour shortage and thereby facilitate larger reductions to the size of the skilled migration intake (crettenden et al. 2014). however, in view of the inevitable time lags between policy initiation and change to graduate numbers, a phased approach to migrant number reduction, which is harmonised with expected future increases in graduate numbers, would be advisable. the 26% increase in australia’s annual number of births between 2001 and 2012 contributed to past increases in demand-related pressures on child care and to more recent school enrolment growth and localised school capacity shortage (abs 2014; goss 2016; guest and parr 2013; mcdonald 2011; productivity commission 2015). the prospective entry into the australian labour force of these 16 parr australian population studies 2 (2) 2018 significantly larger cohorts may contribute to supply surpluses for particular occupations in the absence of responsive changes to skilled migration numbers. the larger sizes of these cohorts could also provide a significant opportunity for strategically-targeted education and training to reduce australia’s future reliance on skilled immigration. of note is that the entry of the larger post-2006 birth cohorts into the australian labour force will roughly coincide with the baby boomer generations reaching older ages with high per capita health and aged care needs, and therefore with increased need for health care sector and aged care sector workers. slowing population growth in australia’s largest cities through a wider dispersal of new immigrant settlement should be a priority policy goal. despite australia’s large land mass and low population density, the concentration of population growth in major cities in general, and sydney, melbourne and brisbane in particular, increased between 2007 and 2017 (abs 2018c; hugo et al. 2015). in 201617 melbourne had a growth rate of 2.7% and sydney and brisbane both of 2.0%, and in combination these three cities accounted for over 70% of australia's population growth (abs 2018c). projections of the populations of sydney and melbourne reaching 8 million by 2061 appear conservative in the light of subsequent trends (abs 2013). it is the projected population sizes of the largest cities, rather than australia’s projected national population size, which i see as the more challenging prospect. a wider geographical dispersal of immigrant settlement and of population more broadly could in theory reduce the extent of transport, housing, infrastructure provision and space-related population problems in the major cities. that said, despite evidence of the improvement in immigrant labour market outcomes in regional and rural australia, with a few notable exceptions (for example byron bay, cairns, darwin, griffith, kalgoorlie, pilbara, shepparton, whitsunday), the immigrant share of population in areas which are distant from the larger cities has generally remained low (abs 2017a; hugo 2015; krivokapic-skoko and collins 2014; massey and parr 2012). the prospective geographical pattern of population ageing may assist dispersal of immigrant settlement beyond the largest cities to a degree. the working age populations of australia’s larger cities are generally younger than those in regional australia. the occupations in which larger numbers of recent skilled stream primary applicants work include accountants, nurses, certain ictrelated occupations and medical practitioners (abs 2018b). in these occupations too the percentages in the later working ages (i.e. 55 and over) are higher for regional australia than for the major cities, and higher for tasmania and generally (but usually less so) for south australia than for the other states and territories (abs 2017a). thus age-related retirement linked to the ageing of numericallylarger ‘baby boom’ cohorts, and the related need to recruit replacements, may increase the proportions of job vacancies in skilled stream eligible occupations outside sydney, melbourne, brisbane and perth. australia’s geography of population ageing will have workforce demand-side implications, as well as workforce supply-side implications, and has the potential to exacerbate health inequity. the ageing of larger ‘baby boom’ cohorts to progressively older and higher health care-using ages will necessitate a substantial expansion of the health workforce (treasury 2015; crettenden et al. 2014). older populations in regional australia, tasmania and south australia face the prospect of ‘doublewhammy’ demand-side and supply-side effects increasing the need for recruitment of immigrant (and local) health professionals beyond the larger cities. the failure of attempts to encourage australian population studies 2 (2) 2018 parr 17 australian medical practitioners to relocate from the cities makes the need for a successful migration-based solution to the prospective doctor shortage all the more pressing (carson et al. 2017). as searle (2018) argues, the most feasible approach to reducing the concentration of population growth in the largest cities involves trying to increase the share of growth of the next tier of cities by population size, such as adelaide, canberra, darwin, hobart, toowoomba, townsville, and (if reclassified to become part of ‘regional australia’ for visa purposes) newcastle. the success of ‘bullet trains’ in dispersing population growth from larger to smaller cities along rail corridors in china points to a potential population-related advantage of an australian high speed rail initiative (zheng and kahn 2014). promoting overseas student study at universities outside the largest cities and providing financial incentives for migrants (especially health professionals) to settle in regional areas of australia may help to disperse migrant settlement a little (tang et al. 2014). in terms of numbers of skilled migrant primary applicants it is the various ict-related occupations which are the most heavily skewed towards sydney and melbourne. thus reductions in quota sizes for these occupations might be expected have the greatest immediate impact in terms of reducing the concentration of numbers in the two largest cities (abs 2018b). in view of limited proven options, a coordinated and funded program of research on the experiences of immigrant settlement and retention in regional and rural australia and comparable countries overseas with a view to identifying a model for achieving a larger-scale dispersion of population is essential (collins et al. 2018; krivokapic-skoko and collins 2014; santoro and wilkinson 2015; taylor 2018). 4. fertility policy family policy and the monitoring and understanding of fertility trends should be important population policy considerations, but not for the ‘pronatalist’ reasons presented by the former howard government (parr and guest 2011). australia’s total fertility rate (tfr) has decreased since 2008 (abs 2014; 2017b). however, contrary to some the belief of some, sustained fertility at replacement level is not necessary to prevent long-run population decline. indeed, under continuation of its average tfr, immigration and life expectancy for 2011-15 over a very long time australia’s population would increase to over 130 million (parr 2018). whilst higher fertility would slow the extent of future population ageing, it would adversely affect the dependency ratio both immediately and over the longer run. higher birth rates may also adversely affect educational provision and attainment and will add to population growth (parr 2006). moreover, the feasibility of substantially increasing birth rates is questionable: the available evidence suggests the effects on birth rates of the former howard government’s introduction of the ‘baby bonus’ (and other simultaneous budgetary changes) most probably was slight (parr and guest 2011). nonetheless, whether, how many, and when to have children are life-changing decisions. the lifetime work, other financial, other time-related, and happiness-related effects of children on parents (and other family members), the lifetime effects of parents (and other family members) on child development, and the ways in which family policies, such as family benefits, child care policy, and leave-related policies, economic policies, social policies, and education policies affect them are fundamentally important issues (craig et al. 2014; guest and parr 2013; luppi and mencarini 2018; markey et al. 2015; myrskyla and margolis 2014; parr 2006; productivity commission 2015). it is also 18 parr australian population studies 2 (2) 2018 important that housing supply facilitates, rather than constrains, attainment of preferred family sizes. for all these reasons, it is supporting research to understand the drivers and family-level implications of fertility patterns, and developing evidence-based policy to enhance family wellbeing, and not birth rate change, which should be the primary fertility policy concern of an australian population strategy (mcdonald 2006). 5. conclusion: the need for population research policy in theory the policy suggestions in this article could: • help to put australia (and especially its larger cities) on a less unpalatable trajectory of population change • aid reduction (which i presume would be the more popular preference) of immigration intake and hence population growth with a view to minimising its economic cost and maximising its mitigation of population-related problems in our major cities • accentuate the value of strategically educating and training younger generations of australians, and enhance their future integration into the labour force • aid the geographical alignment of australia’s national workforce with its ageing population, and • promote the enhancement of family life in australia. however, the realisation of such outcomes will depend, at least in part, on a broad range of related research being undertaken. three key priority areas for research are: 1) forecasting fertility, mortality, trans-tasman migration, australian citizen return, international student movement, emigration, and (most importantly of all) subnational population change 2) analyses of the relationships between immigration selection criteria and immigrant labour market outcomes, workforce ageing, retirement trends, trends in education and training, and work, housing and family combination, and 3) developing experimental ideas for and analysis of immigrant settlement experience and retention outside australia’s largest cities. ensuring that the requisite research is undertaken will require establishment of a coordinated, funded program of population research and a systematic expansion of australia’s pool of suitablytrained researchers. currently, what little australian population-related research is conducted is a matter of the whim of a relatively small and ageing pool of researchers who compete against researchers from other disciplines for scarce research funding, and whose jobs are a by-product of staffing decisions which are not necessarily taken with a view to the broader national interest. the coordination and funding of the development of a next generation of demographers and other population researchers through dedicated scholarships for postgraduate and postdoctoral research is also critically important if a research-informed population policy for australia is to be sustained over time. australian population studies 2 (2) 2018 parr 19 6. key messages • in view of the wide-ranging and long-lasting implications of population change, australia should adopt a population policy. • changing the total number of permanent migration visas issued is the key policy lever though which the federal government may influence population trends. • the implementation of changes to skilled migration numbers should be phased over time and integrated with changes to education and training policy. • the growth of the population sizes of the largest cities presents a more challenging prospect than national population growth. a wider dispersal of immigrant settlement should be a priority population policy goal. • population ageing could create opportunities for achieving a wider dispersal of migrant settlement. • enhancing family wellbeing, and not birth rate change, should be the primary concern of 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fertility policy 6. key messages references australian population studies 2019 | volume 3 | issue 1 | pages 1-12 © parr 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org understanding the motivations for return migration in australia angélique parr* the university of queensland * email: angelique.parr@uqconnect.edu.au. address: po box 77, drummoyne, nsw 1470 paper received 15 february 2019; accepted 19 may 2019; published 27 may 2019 abstract background return migration is often overlooked by traditional analyses of internal migration. why people return has received even less scrutiny. relatively few migrants make a return move, so there is clearly something noteworthy about these people and their circumstances that trigger such a move. aims this paper explores why people make return moves in australia. data and methods migration histories were collected using semi-structured in-depth interviews; content analysis of interview transcripts was undertaken. results people return for a wider range of reasons than is indicated by neoclassical economic theory. some of the moves are linked to significant life events such as post-school education and employment. returns also occur for less tangible factors such as amenity and climate, connections to family, friends and the extent to which a place “feels like home” are equally important. conclusions a broader explanatory framework is required to explain why people return. the integration of migrant stories into more traditional migration analyses enriches the story of internal migration. key words internal migration; return migration; motivations; australia. http://www.australianpopulationstudies.org/ mailto:angelique.parr@uqconnect.edu.au 2 parr australian population studies 3 (1) 2019 1. introduction australia’s internal migration system is complex, comprising many types of moves over differing spatial and temporal scales. one type of move that is usually overlooked by traditional analyses is that of return migration. it is the event where people who moved to a new place of residence return to live at their former home or region at a later date (bell and hugo 2000). in some contexts it can be better conceptualised as part of circular migration rather than a discrete form of migration in its own right. return migration acts as a counterbalance to the dominant direction of migration flows between areas, and previous research has established that return migrants are a distinctly different group compared with other migrants in terms of both their demographic character and motives for moving (da vanzo and morrison 1981; long 1988; newbold and liaw 1990). our understanding of return migration is bound by the data used to observe it. in australia this is the census, and returns to a previous place of residence are observed over the five-year intercensal period. but returns may occur after an absence almost as long as a life span. while the use of geo-political boundaries can obscure its true spatial extent, migration must cover a sufficiently large distance to change the activity space within which a person functions on a daily basis (boyle et al. 1998; parr 2018). five dimensions (intensity, who moves, where, when and why) are recognised as fundamental perspectives in migration studies (bell 1992; long 1988), but one dimension, ‘why people move’, has received far less scrutiny than the other four. given that relatively few migrants make a return move (bell 1996a; parr 2018), there is clearly something noteworthy about such individuals and the specifics of their circumstances that trigger such a move. drawing on the results of a recently completed analysis of return migration in australia (parr 2018), this paper begins to fill out the missing “why” in the return migration story. the paper begins with a summary of recent research on the motivations for return migration. it then outlines the explanatory framework, the dataset and methods used in the analysis. the body of the paper recounts the stories of a group of australian residents who have made return moves. the paper concludes with a brief discussion of the implications of the findings for both migration theory and methods. 2. background substantial insight into the motivations for return has derived from studies of international migration, particularly the movement of labour migrants (lidgard and gilson 2002; reagan and olsen 2000; stalker 1994). comparatively little has been written in relation to internal migration, although the reasons for international and internal returns appear to have many similarities. king (1996) found there are many reasons, which change over the life course. a swedish study looking at people who returned to rural areas where they grew up is the most comprehensive so far (amcoff and niedomysl 2013; niedomysl and amcoff 2010). return migrants were more likely to report social reasons for moving than reasons related to employment or education. moving close to friends was important for divorcees and people returning to sparsely populated areas. studies of the impact of out-migration from rural scotland found that people return for a range of personal and employment-related reasons (stockdale 2002, 2006). other work reveals a multiplicity of motivations to return, with social connections a major factor (alexander 2005; bijker et al. 2012; stockdale 2006; wang and fan 2006). australian population studies 3 (1) 2019 parr 3 an australian study of young people who returned to tasmania noted the importance of lifestyle and being close to family (easthope 2006). having a sense of community and belonging, or ‘a place to call home’ appears to influence the decision to return (stockdale 2002). return moves may be linked to significant life events. in this paper such events are categorised into four types: economic, education, family-related and ageing. but if life events alone are responsible, the probability of returning would be considerably higher than is observed in australia (parr 2018). the reasons for return must therefore be much broader in scope than those offered by the traditional neoclassical framework, which has been criticised for not adequately explaining the reasons for internal migration (long 1991). they may range from macro-scale social, political and economic forces to micro-scale individual behaviour and preferences. the emphasis here is to gain an understanding of the motivations of the individual migrant, which can change over the life course (jeffery and murison 2011; king 1996; lundholm et al. 2004). this study draws upon four explanatory frameworks to understand the motivations for return. a life course perspective has been combined with lee’s push–pull model (lee 1966), wolpert’s (1965) place utility model and faist’s (2000) theory of meso-scale factors to argue that significant life events, in combination with other factors, will result in return migration. people tend to migrate to familiar places (boyle et al. 1998 p. 64) and the personal ties, familial ties and social networks that connect a migrant in some way to a place where they have lived in the past will have an additional strong pull (mulder and malmberg 2014). this paper proposes that such meso-scale considerations are just as important as other factors in explaining the selective nature of return migration. they create connections or moorings that act more strongly to draw a migrant back to a previous place of residence than other factors that would have them move to a new location. 3. data and methods motivational factors associated with internal migration are seldom captured in traditional data sources (stillwell and garcia coll 2000). in particular, bell (1995) pointed to the lack of information about why people move as a major deficiency of australia’s census. most previous studies of return migration have inferred the reasons from migrant characteristics (bell 1996b; currie and hallie 1988; long 1988) and it is only recently that research has begun to look at this directly. understanding more about the motivations for return migration can only be achieved by looking elsewhere to alternate data sources. this study has taken an important step by using detailed migration histories to examine this issue directly. qualitative research methodologies that study human behaviour and the social world are used to understand why people move. this paper reports on information from the migration histories of 22 people who returned to a former place of residence from elsewhere in australia. applying a purposive sampling approach, the study participants were recruited from the 50+ registry of the ageing mind initiative at the university of queensland, and networks at the new south wales department of planning and environment. eligible participants had changed residence in australia at least twice, with one of these moves being a return to a place they had lived in sometime in the past. no constraint was placed on the type of place to which they returned, such as the participant’s place of birth or where they grew up. but any change of residence had to be of at least six months’ 4 parr australian population studies 3 (1) 2019 duration and across a sufficiently large distance to alter the spatial patterns of the participant’s dayto-day life. the size of the study group ensured that the diverse range of behaviours and underlying motivations would be revealed from the migration histories. this group was not selected as a representative sample of return migrants in australia. detailed migration histories and associated stories about people’s lives were collected using a semistructured questionnaire. participants recounted the places they had lived in from birth to the time of the interview, and the life events or other circumstances associated with any moves. as an aide memoire, a life grid (bell 2005) was concurrently used during each interview to create a written record of information provided. a content analysis of the interviews revealed the migration pathways of these people, a wealth of information about the life events linked with these moves, and the underlying motivations as recounted in the migrant’s own words. information from the interviews was indexed and categorised to identify both similarities and differences. this did not follow a preset coding frame, but one that was developed while reviewing the transcripts (flowerdew and martin 2005). the study group ranged in age between 25 and 88 years and lived throughout australia, including metropolitan regions and smaller towns (see figure 1). up until the time of the interviews, the 22 migrants had made more than 230 moves in total, including 55 returns. figure 1: reference map of places where study participants lived at the time of interview source: the author australian population studies 3 (1) 2019 parr 5 4. results: reasons why people return the migration histories used in this study revealed the complex nature of human mobility and the extent to which changes of residence affected, or conversely were influenced by events, people and places. the names of all participants cited here have been changed to maintain anonymity; their age given in the text was as at the time of the interview. economic factors family and economic factors were the most frequently stated reasons for return. economic factors related mainly to employment, but employment was seldom the only reason for a return move – multiple reasons could be identified. a job often facilitated the return, rather than being the key reason for it and often explained a considerable time lag between the decision to move, and the actual return. transfers with the same employer facilitate returns. william, now 58 years old, moved frequently with his job in the armed forces to military bases scattered across australia. his employer had an expectation that staff would move about every couple of years, sometimes returning to a previous posting. natalie was one of the more mobile young people interviewed. she moved several times between melbourne and canberra, with the first return to canberra occurring after graduation. she found work using networks: ‘i had a casual job when i was studying and basically, i just walked straight back into that. so, i made sure i had that before i moved back and just moved back into the job. so, i guess it wasn’t [about going] back … unemployed and looking for a job. i went back to that casual job and then started looking for a permanent job when i got back there.’ (natalie, 33) previous research concluded that return migrants were often unemployed (morrison and da vanzo 1986). this was not evident from the interviews undertaken for this study. being unemployed may have contributed to the decision to return, but people were seldom unemployed when they moved; many had already found a job. housing was another economic factor, especially for younger participants. natalie’s recent move back to melbourne had motives other than a job transfer: ‘i had planned to get into the property market for a while. i’d wanted to buy a house and it was a bit out of my reach in canberra, whereas melbourne offered quite more options in that respect. so that was, i guess, my main motivation.’ (natalie, 33) economic necessity has forced some people to return. melanie was a young professional living in sydney who moved home in her mid-thirties because: ‘ … i was pregnant … there was no maternity leave. … there was no income going to be coming in, so … no way of supporting myself. i’m a single mum. so, it wasn’t planned [that i] move home with mum and dad at 38. that’s the last thing i wanted to do ... [but] i need their support at this point in time with babysitting and everything.’ (melanie, 41) 6 parr australian population studies 3 (1) 2019 family-related a variety of family-related reasons featured strongly in the decision to return. naomi returned to melbourne with her husband after several years in brisbane because: ‘… we were at the point in our life where we were starting to think about having kids. and we decided that it would be best to be around family … for the support network. … the only thing that would have kept us [in brisbane] would have been if my mum and dad had moved up.’ (naomi, 33) faye grew up in regional victoria and moved numerous times. her first return to ballarat was at the age of 35 with her young family, because of her ageing parents. ‘we needed to be closer to them ... they came and looked at some places [in melbourne] but they didn't want to come. they didn't want to move.’ (faye, 82) returns have also taken place because people missed family and wanted to see them more often, or as in the case of ellen, because they were homesick. ‘i came back to melbourne because i was really homesick. i didn't really adjust to sydney very well … a lot of bullying, a lot of hostility, it was quite bizarre.’ (ellen, 48) education the third dimension, education, was a contributing factor when people returned as younger adults. ellen first left melbourne aged 20 to follow a boyfriend to sydney but returned a few years later to start a writing course at deakin university. thelma left brisbane in her early twenties to attend bible college in melbourne but returned a few years later to complete her accountancy qualification. wendy returned to brisbane because of a desire to send her children to the same school that she had attended. ‘i enrolled my girls [at my old high school] when they were very young; i wanted them to get a good education, to get more attention based on their merit rather than socio-economic disadvantage.’ (wendy, 56) ageing returns related to ageing did not feature as much as expected; and returns were usually made to care for elderly parents, rather than because the return migrants themselves were aged. as well wanting to put her children through high school, wendy returned to brisbane to help care for her elderly mother. ‘i’ve got two brothers who are really busy. ... so, there’s no one really to look after mum and rather than park her in a home, which we didn’t want to do, it was about meeting her needs, and meeting my girls’ [education] needs [at the same time].’ (wendy, 58) australian population studies 3 (1) 2019 parr 7 erin was one of the few cases whose return was a lifestyle choice related to ageing, rather than a necessity. in 2003 she moved with her young family to adelaide to live closer to her father. although only in their early forties, erin and her husband were starting to think about where they wanted to be living, as they got older. they decided to settle in adelaide until ‘one day my husband came home and said, “you know what, i don’t imagine retiring down here [in adelaide]” … so he started looking for a job and six months later we moved back to sydney’. (erin, 47) the migration histories of the oldest study participants support litwak and longino’s (1987) findings that the onset of age-related disability does not result in return migration. returns had occurred some years earlier, in early retirement. the most recent moves were generally local moves into aged care facilities. ties to place a variety of factors were consistent with faist’s (2000) meso-scale explanations for return. the links to family and friends who remained behind were a particularly strong motivator. karen was a young child when her parents moved the family to dubbo, a regional city in central new south wales. but the family soon returned to sydney. ‘… [my parents] missed family and friends, and both their parents were getting on and my grandparents were getting sick, … so they wanted to go back ... they were thinking that they needed to return home to be closer with the family there.’ (karen, 46) family and friends can take pressure off the return move, providing a place to stay or some other form of support as migrants settle back in after a return move. links with other networks, particularly social ones or with previous employers also made resettling an easier process. erin and her family found their return from adelaide to sydney easier “… because we kept all the relationships going with friends and stuff. we just started up with where we left off.” (erin, 47) another strong theme to emerge was the sense that the place to which people had returned was somewhere that was very familiar and where they felt happy. such places were often where people had grown up. thinking about the places she had lived other than sydney, karen remarked: ‘sydney felt like home … the surroundings [in cairns and the central coast] were so different to what i remember in sydney as a child. i think your understanding of a place starts from when you’re a child and yeah, as you get older that anchors you to the way you think and react to certain things and i think that’s – it just was different … this isn’t where i grew up. this isn’t my familiar place’ (karen, 46) having ties to a place, or a sense of identity, was a strong theme that featured repeatedly, among migrants of all ages. ‘melbourne is my home; it’s where my friends and family are’ (leslie, 58) 8 parr australian population studies 3 (1) 2019 ‘melbourne’s my home and i love my footy’ (ellen, 48) ‘sydney is always home’ (vivian, 59) ‘once a queenslander, always a queenslander’ (henry, 74) karen is also an example of someone whose ties to a place carried across the generations. although she had many good memories of living in dubbo: ‘my parents brought the family back to sydney because dubbo didn’t feel like home. they never felt at home there. … so yeah, back to where they felt was home. … the job promotion [in dubbo] was good, young children, cheaper housing, all those things, but they just felt they wanted to come back home to the bigger city.’ (karen, 46) amenity another strong consideration was amenity. natalie’s frequent returns to canberra were not just about work or education: ‘i really liked the lifestyle in canberra. i was living quite far out of the [central] city in melbourne, so i was really feeling the distance and the lack of convenience which is not an issue at all in canberra. … i guess i’m not much of a city person so [canberra]’s got a country atmosphere but with all the advantages of living in a city … if you do feel the need for a bit of city contact, you’ve got sydney just up the road as well. so, i feel like canberra’s very wellplaced in a lot of respects … it had everything i could want … and i actually liked the weather as well, despite what everyone says about it.’ (natalie, 33) sharon (56) moved between melbourne and darwin on several occasions, for a series of short-term and contract jobs. two reasons had her looking back to these two cities time and again. the melbourne seaside suburb in which she lived had a comfortable familiarity, a sense of being home. many locals also had similar values to her. the other factor, common to both darwin and melbourne, was her affinity with the natural environment. she loved being near the ocean and living in neighbourhoods with lots of palm trees. on another occasion, sharon had lived in canberra but soon returned to melbourne because “… two to three years was enough. i was disoriented as i was too far away from the sea.” the climate of a location was mentioned by other participants as an influence on the decision to return. for example, william and his wife were happy to have a return posting to darwin as they liked the city’s climate. but climate could also push people away, encouraging a return to a previous place of residence. in 2009 leanne and her husband moved from perth to brisbane to be with their granddaughter but left two years later because “it rained all the time … so we were glad to come back to perth. the weather played a huge part on our decision to come back” (leanne, 55). another reason why karen’s parents brought their young family back to sydney from dubbo was that they did not like the temperature extremes. australian population studies 3 (1) 2019 parr 9 ‘summer, dad used to say was stinking hot and the winter freezing, and they remembered the toilet would block up, it would freeze.’ (karen, 46) other factors besides climate, a desire for a change of pace can underpin a return move. thelma spent more than 20 years living in sydney and was finally able to return home to brisbane with her family: ‘i married a sydney fellow. i produced three sydney children. and there was no way, even though i would have loved to come back to queensland, there was no way i would have initiated that. i didn't feel i had the right, to do that. but my husband was a service technician and he was driving all over sydney. it drove him barmy and he wanted to get out.’ (thelma, 72) for her part, karen was very pleased to return to sydney: ‘i was very happy to move back to sydney because i grew up there and it was familiar and it was convenient and i was young and i had the culture and the food and the shops and my work friends and that whole lifestyle. it was good.’ (karen, 46). 5. discussion and conclusions the aim of this paper was to supplement the often overlooked, but now growing, body of work about the reasons for return migration. migration histories are a rich source of information concerning return moves of people living in australia. findings revealed that people return for a wider range of reasons than is indicated by neoclassical economic theory and support the suggestions from other researchers (bell and hugo 2000; cromartie and stack 1989) that a broader more inclusive conceptual framework is needed to explain the selectivity of people who return. the framework used in this paper, which combines a life course framework with macro-scale and meso-scale explanations, is a good starting point. results reveal that the reasons why people make a return move are as varied as the people themselves. some of the moves are linked to significant life events such as post-school education and employment. returns are also linked to other, less tangible, factors such as amenity and climate. the connections to family, friends and other networks and the extent to which a place “feels like home” are just as important. these less tangible factors are much harder to measure using conventional data sources and are outside the realm of the frameworks normally used to explain return migration in developed countries such as australia. the meso-scale framework developed by faist (2000) is a very useful way to explain more of the reasons for return migration revealed in the migration histories. the motivations for return have similarities with the motives for internal migration in general. work is not always a critical reason for moving in either case. social and environmental considerations are important and the reasons for moving can be complicated. some of the motivations revealed in this paper may also explain why return migrant selectivity is not always distinct. the reasons for the 10 parr australian population studies 3 (1) 2019 return may bear no connection to the socio-demographic character of the return migrant. for example, returning to care for elderly or sick family members may not be related to age, gender, occupation or income. it may have more to do with the strength of family ties and a sense of duty to care for others in the family. the histories used in this study were not intended to be representative of the people and patterns revealed by census analyses. rather, the aim was to illustrate what could be revealed about return migration in australia using alternative methods and different data sources. the collection of migration histories is always fraught with issues. difficulties with recall of the timing of events were evident with some of the older participants and post-facto rationalisation of the choices people make is a known problem. it has been suggested that people look at their past with rose-tinted glasses to justify their decisions. there is no obvious way to get around this, but these issues need to be recognised. limitations aside, the wealth of information provided by migration histories demonstrates that this is an extremely rich source of data about return migration. it also complements the precision of quantitative analysis habitually undertaken by demographers and population geographers. the value of integrating this material with the findings derived from conventional census-based analyses is strongly encouraged and broadens our understanding of australia’s internal migration system. key messages  understanding why people return to a place helps explains the patterns of movement.  the reasons why people make a return move are as varied as the people themselves.  a job is not the only reason why people return. some returns are linked to significant life events. ties to place, family and friends, the climate and environment are also important factors.  that a place “feels like home” is also an important reason why people return.  migration histories are a rich source of information about why people return. they enhance research that traditionally relies on data from australia’s census. acknowledgements this research forms part of a larger study supported by the australian research council discovery grant dp 0451399: understanding the structure of internal migration in australia. i am grateful for the helpful comments of the anonymous reviewers on an earlier draft of this paper. references alexander j t (2005) they're never here more than a year: return migration in the southern exodus 19401970. journal of social history 38(3): 653-671. amcoff j and niedomysl t (2013) back to the city: internal return migration to metropolitan regions in sweden. environment and planning a 45(10): 2477-2494. bell a j (2005) 'oh yes i remember it well!' reflections on using the life grid in qualitative interviews with couples. qualitative sociology review 1(1): 51-67. australian population studies 3 (1) 2019 parr 11 bell m (1992) internal migration in australia: 1981-1986. canberra: australian government publishing service. bell m (1995) internal migration in australia 1986-91: overview report. canberra: australian government publishing service. bell m (1996a) repeat and return migration. in newton p w and bell m (eds.) population shift: mobility and change in australia. canberra: australian government publishing service; 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39–51 © maertens and taylor 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org improving population retention in northern australia: clues from german-born territorians anita maertens* charles darwin university andrew taylor charles darwin university * corresponding author. email: anita.maertens@cdu.edu.au. address: northern institute, charles darwin university, ellengowan drive, darwin, nt 0909 paper received 9 march 2018; accepted 4 may 2018; published 28 may 2018 abstract background population growth rates in many parts of northern australia have slowed considerably in recent years. governments are interested in identifying northern migration ‘markets’ as potential targets for a mix of marketing and policy-based approaches to improve population attraction and retention. in the northern territory (nt), german-born residents present an interesting case study. many are long-term residents (‘sticky’), highly educated, in professional jobs and say they are likely to stay. aims we profile and report on a study of german-born nt residents as one important international market for offsetting population losses. understanding factors which have contributed to the attraction and retention of this group may help to inform policies and initiatives to improve the population position of the nt and northern australia more broadly. data and methods data for the paper is sourced from the 2016 abs census of population and housing (census) and the 2017 german territorian survey (gts) conducted by charles darwin university. results german-born residents are a relatively immobile (‘sticky’) and educated population group in the nt with a high ratio of females. many of those surveyed, in particular those who had arrived as working holiday makers or tourists, exhibited little or no intention of leaving. lifestyle factors, climate and job opportunities ranked highly in decisions to stay. conclusions the study of german-born territorians holds promise for developing targetted niche migration initiatives to address skills and population deficits in the nt and northern australia. analysis of responses to the gts highlighted opportunities for recruiting skilled women and the importance of tourism as a source for labour supply and population growth. key words population retention; northern territory; northern australia; overseas migrants; german-born; german migration; female migration; labour market. http://www.australianpopulationstudies.org/ mailto:anita.maertens@cdu.edu.au 40 maertens a and taylor a australian population studies 2 (1) 2018 1. introduction northern australia, the region north of the tropic of capricorn, comprises 40 per cent of the continent’s land mass yet is home to only 5 per cent of the population. the north has been assumed by various proponents to hold untapped resources with capacity for significant economic growth and population growth to assist in underwriting national prosperity. it is the focus currently of national policies for growth and development under the developing northern australia agenda (australian government 2015). however, aspirations for the north historically have fallen short in successive ventures, and population growth rates in many parts have slowed considerably recently (figure 1). in the period 2002–2003 to 2009–2010, for example, growth was beyond 2 per cent, some 0.5 per cent higher than the rest of australia. however, by 2015–2016 population growth was estimated as in decline. while peaks and troughs have been evidenced in the past, and often associated with resource industry fairings, the current downturn is prolonged and substantial. figure 1: population growth rates for northern australia and the rest of australia, 2001–2002 to 2015–2016 source: abs cat. no. 3218.0 – regional population growth, australia (various years); note: northern australia is defined here as all of the nt and all areas north of the tropic of capricorn in queensland and western australia (australian government 2015 p. 132). complex mixes of factors, which vary between regions, have likely contributed to subdued population growth lately across northern australia. a recent report for the northern territory (nt) government (taylor and carson 2017) identified some key trends and issues impacting population change including: • major (up to 50%) absolute declines in the attraction of people from some interstate migration markets, including families with children and early career workers (especially women) • increased departures for early career women and pre-retirees, with the former accounting for 60 per cent of female resident flows to and from the nt • a long-term decline in the preference of internal migrants to gravitate to australia’s northern jurisdictions and a growing perception of high risks in doing so • the end of australia’s ‘mining boom’ • technological advances circumventing the need for some resource, construction and agricultural jobs to be located in situ australian population studies 2 (1) 2018 maertens a and taylor a 41 • structural changes to the demographic characteristics of northern populations, including workforce and general population ageing • changed labour practices for resource and other sectors with the increasing engagement of nonresident workers who are not necessarily counted in official population estimates. emergent literature on the economic demography of northern regions has highlighted similar issues affecting populations in remote and sparsely populated areas of other developed nations, such as sweden, greenland, canada and norway (see, for example, taylor 2016; carson et al. 2011). the root cause of population downturns for such places has been a loss in their capacity to attract new residents in the same numbers as during high growth periods, combined with increased departures of residents of certain age or life stages (e.g. youth in northern sweden). the loss of appeal of the north to some source markets, as evidenced particularly in the nt, has contributed to net negative migration flows for northern australia. while national migration policies help to determine the volume of international migrants settling initially in northern regions, targeted approaches need to align local ‘unique selling points’ with the mobility motivations and aspirations of identified intake markets (taylor, payer and brokensha 2015; taylor 2018). although the availability of jobs is important for population retention, the issues identified by taylor and carson (2017) highlight the increasing interplay of other factors which must be considered by governments in developing marketing and policy-based approaches to support population migration and growth. in this sense, markets may be source regions or nations or sub-populations characterised by life-stage or other segmentation (e.g. early career workers, pre-retirees or skilled migrants for specific occupations). overseas-born residents offer the potential to bolster population growth and development. while northern areas generally attract an annual share of overseas migrants broadly equivalent to their share of the national population, immigrants from some source countries appear to have a greater disposition for residency in the north than other internal or international migrants. of particular interest are migrants from source countries who continue to arrive, are present in substantial numbers and have a propensity to ‘stick’ in the north ( i.e. a longer average term of residence compared both to other migrant groups and the overall population). with a long history in the nt, german-born residents are one source of international migrants who appear to meet the criteria of relatively large numbers, continued arrivals and relative ‘stickiness’ as residents. data from the australian bureau of statistics (abs) 2016 census of population and housing (census) showed that their length of residence in the territory far exceeds most overseas-born migrant groups, with 38 per cent in 2016 having arrived between 1941 and 1980 compared with 18 per cent for other overseas-born groups. understanding the complex factors contributing to this migrant sub-group coming to and staying in the nt may provide insights for strategies to attract and retain other source markets from australia and overseas. the purpose of this paper is to report on a 2017 study of german-born territorians. in the face of nine successive years of low population growth and apparent decline in attractiveness of the nt to particular market segments, overseas-born migrants offer the potential to bolster population growth and development. our aim is to explore push–pull factors that influence population attraction and retention for this particular sub-group, with a view to informing strategies and responses for attracting other niche markets and addressing population attrition in the north. prior to reporting on the study, we first profile the german-born population of the nt through analysis of australian census data. 42 maertens a and taylor a australian population studies 2 (1) 2018 2. a profile of the german-born territorians people of german descent have a long association with the nt. their roots include early european exploration and missionary activities from the late 1800s. german lutheran missionaries were prominent in establishing and running aboriginal mission settlements in central australia. two prominent proselytisers were carl strehlow, who studied and recorded arrernte (sic. ‘aranda’) and loritja (western desert) languages in the alice springs region (kimber 2008 pp. 557–559), and friedrich wilhelm albrecht, a missionary of german–polish descent who spoke against the removal of aboriginal children from their mothers (henson 2008 pp. 8–9). the migration of german-born people to the nt continued in ensuing decades and increased post1940 as a result of dislocations associated with world war ii. the german club was established in darwin in 1967 and darwin’s famous ‘beer can regatta’ was co-founded by lutz frankenfeld, a german-born long-term resident, in 1974 (german club darwin 1987; 2002). there have also been significant flows of german-born tourists to the nt. in 2017, germany was the third ranked source market for international visitors to the nt, with 31,000 german visitors, and sixth ranked source market for visitors to australia as a whole. by 2016, there were around 1,000 german-born residents in the nt, or 0.5 per cent of the total nt population. meanwhile, 1,685 residents had at least one german-born parent and 8,734 declared german ancestry (abs 2017). in 2016, almost 70 per cent of german-born residents lived in the greater darwin area, 12 per cent in alice springs and the remainder elsewhere in the nt (tourism nt 2017). data from the 2016 census indicate that more german-born women than german-born men were living in the nt in 2016 with a ratio of 124:100. this compares to an equivalent ratio of 92:100 for the nt’s non-indigenous population as a whole and 89:100 for all european-born residents. this female dominance appears to be a recent phenomenon resulting from a plateauing in male, but not female, german migration. professionals (24%), technicians and trades workers (16%) and managers (15%) were prominent occupational classifications. german-born women had higher educational attainment than their male counterparts and other resident groups: 12 per cent of german-born women had postgraduate degrees compared to 6 per cent of their male counterparts and 7 per cent of all overseasborn nt residents. in 2016 the median age of german-born residents was 51 years. this was much higher than that for all overseas-born (38 years) and australian-born (29 years) nt residents. in terms of occupations, professionals (24%), technicians and trades workers (16%) and managers (15%) were prominent. almost 30% of all german-born women were professionals. most germanborn territorians were in relationships without children (62%), compared with all overseas-born (41%) and australian-born (32%) residents. german-born women were younger on average than their male counterparts. 3. data and methods in 2017 current and former german-born nt residents were recruited for an online survey, the german territorian survey (gts), administered by researchers at charles darwin university. the survey explored a range of demographic characteristics and pull–push factors influencing nt residency. participants were recruited via german social groups in alice springs and darwin, social media (e.g. facebook), email distribution lists and the media. complete responses were received from 135 participants. australian population studies 2 (1) 2018 maertens a and taylor a 43 the survey elicited experiences of living in the nt with a mix of multiple-choice and open-ended questions which were subsequently coded. the study was limited by small participant numbers due to the recruitment methods and online survey format described above. survey respondents tended to be younger, female and more highly educated than the nt german-born population as a whole. this was attributed in part to the survey method and higher likelihood of females participating in such studies. nevertheless, the study provides important baseline information to extend and explore key themes in association with census data. 4. results gts respondents tended to be younger, female (80%) and more highly educated (53% had a bachelor degree or above) relative to the german-born nt population as a whole. most were couples with children (47%) or couples without children (30%). this is a little at odds with the findings from the 2016 census which found that most (62%) german-born nt residents were in relationships without children, and likely reflects the recruitment method (as noted). of the 135 respondents who had migrated to the nt between 1961 and 2017, 103 (76%) were living in the territory in 2017. the geographic distribution of gts participants who still resided in the nt was consistent with the census, which recorded that two-thirds were resident in greater darwin and the remainder elsewhere in the nt in 2016. 4.1 why respondents moved to the nt the primary reason for moving to the nt for 40 per cent of respondents was employment (a job offer or work opportunities). almost 25 per cent arrived as tourists on a holiday or working holiday visa who decided to stay (figure 2). other motivations included: personal connections (13% family and friends; 10% a partner); lifestyle factors (9%); seeking an escape or adventure (5%); or study or research purposes (4%). figure 2: ‘why did you move to the nt?’ source: gts 2017. 44 maertens a and taylor a australian population studies 2 (1) 2018 reasons for coming to the nt varied considerably by gender. only 37 per cent of german-born women moved for a work-related reason, compared with 61 per cent of men. interestingly, 25 per cent of women reported that they were on a working holiday and decided to stay, compared with just 11 per cent of men. while jobs featured highly in reasons reported for migration decisions, other factors were also important, such as lifestyle (over 20% for men). in addition, one-fifth of male respondents and a quarter of female respondents cited family, friends or partners as motivations for moving to the nt. 4.2 what respondents loved most about the nt lifestyle factors received the highest score for what people loved about the nt (65%), followed by work opportunities (46%), climate (42%) and social aspects (38%) (figure 3). other responses included the attractive natural environment, low population density and cultural aspects (aboriginal culture, multicultural communities, open-minded communities). figure 3: ‘what do you love most about the nt?’ source: gts 2017. both male and female respondents noted that careers in the nt were a big drawcard for women, especially for those highly qualified for whom there were diverse career opportunities (e.g. in the arts, health and social services), good leave conditions and decent salaries. other respondents thought women might be looking for adventure in the nt with its ‘frontier’ appeal, whereas males seemed to be more work driven. 4.3 what’s not to like? climate was a major concern for many respondents, both for those still resident in the nt and for those who had left. distance from family and ageing parents were prominent reasons for exiting, with others citing a better lifestyle, work opportunities and new experiences or adventures elsewhere (figure 4, next page). the gts included a question about potential areas for improvement. cost of interstate travel was noted as the biggest problem, closely followed by the cost of housing/living (figure 5, next page). interestingly, although high costs were noted as important, this would not necessarily cause many australian population studies 2 (1) 2018 maertens a and taylor a 45 respondents to move away (figure 4). in available comment fields, over 5 per cent of respondents highlighted a need to invest in renewable energy, focus on sustainability issues and protect the environment and wildlife. figure 4: ‘why did you leave?’, ‘why would you move away?’; responses combined source: gts 2017. figure 5: ‘where do you feel the nt most needs to improve?’ source: gts 2017. note: score is a weighted average where 1 = no need to improve and 5 = extreme need to improve. 4.4 likelihood of leaving the nt when asked how likely they would be to leave the nt, 42 per cent of respondents still in the nt said they had little or no intention of leaving; 29 per cent said it was ‘somewhat likely’; and 29 per cent ‘very’ or ‘extremely’ likely. of the respondents who had arrived in the nt as working holiday makers or tourists, 84 per cent said they had ‘no intention of leaving’, and none said they were ‘extremely likely’ to leave. figure 6 (next page) presents survey results for what respondents loved most about the nt crossclassified with likelihood of leaving to identify motivations for staying or leaving. over 70 per cent of 46 maertens a and taylor a australian population studies 2 (1) 2018 those with ‘no intention of leaving’ loved the nt climate, while climate scored lowest for those ‘extremely likely’ to leave. lifestyle opportunities also received a high rating (60% or above) by all respondents, except those ‘extremely likely’ to leave. work opportunities were the biggest factor for those ‘extremely’ and ‘very likely’ to leave. in a follow-up question, respondents reported that they were more likely to migrate to other parts of australia than overseas. figure 6: ‘what do you love most about the nt?’ responses by likelihood of leaving nt, current nt resident responses source: gts 2017. 4.5 regional differences a number of regional differences were evident in the responses to some questions. climate more strongly influenced likelihood of leaving for top end residents compared to residents in central australia; proximity to asia was more of a point of attraction to those in the north and interstate travel costs an issue for those in the centre. darwin residents, in particular, saw a need to improve public transport, while climate and work opportunities scored more highly as positive factors for residents in central australia. respondents across the nt rated lifestyle and nature highly. 4.6 education and employment the gts identified that 34 per cent of german-born residents were not working in a field related to their highest educational attainment. a significant proportion of these (30%) had a postgraduate degree. some commented that they were overqualified for their current roles, positions were not in their specialised field or that it was impossible to get professions recognised or accredited in australia. respondents not in the workforce stated they were retired, full-time parents or studying. 4.7 personal relationships figure 7 shows that many female respondents (55%) were in a relationship with an australian-born partner at the time of survey. conversely, most of the male respondents in a relationship had a german-born partner (50% of all males). similar proportions of women (13%) and men (15%) stated australian population studies 2 (1) 2018 maertens a and taylor a 47 they were not in a relationship. some respondents speculated that australian partners would not be able to cope as well with ‘culture shock’, language barriers and the climate if they moved to germany together. figure 7: ‘what is the country of birth of your partner or spouse’ (if applicable)? source: gts 2017. 5. discussion 5.1 opportunities for early career women results from this study indicate that german-born nt residents are a promising sub-group for improving population growth prospects in northern communities. the relatively young age profile, education and qualifications of german-born women speak to the noted declines in arrivals and increased departures of early career female workers. although women have traditionally been viewed in (now dated) migration literature as dependants, ‘moving as wives, mothers or daughters of male migrants’ (docquier et al. 2012 p. 251), the gts demonstrates the reach and embedment of skilled female migrants into even the most remote parts of australia. highly educated female professionals in our study were able to seize appealing career opportunities, especially in the health, social care and arts and culture sectors, and embed themselves in the nt lifestyle. despite the blurring of boundaries between the male and female workforce over time, women often still seek and are recruited for jobs where they enjoy more job security and a sense of contributing to a greater good, rather than focusing on extrinsic, principally financial rewards (carson et al. 2010 p. 126). gts participants suggested that the largely resource-based territory economy did not necessarily offer jobs in fields attractive to highly qualified german men, who found more lucrative opportunities interstate or overseas. the nt’s occupational and industry mix, itself reflective of the north of australia overall, appears suited to the professional aspirations of german-born female migrants. it is likely conducive to other similar-minded international female migrant groups, and therefore an ideal market for informing population initiatives and policies for the north. 48 maertens a and taylor a australian population studies 2 (1) 2018 5.1 how does the gts compare with other studies? results from the gts were compared with a german survey on population mobility, international mobil (svr 2015), the 2006 territory mobility survey (tms) (charles darwin university 2008) of current and former nt residents and a recent study on ‘lifestyle migrants’ in northern sweden (carson, carson and eimermann 2017). compared with current and former german migrants in international mobil and all non-indigenous territorians in the tms, gts respondents’ specific migration motives stood out. while international mobil’s international german migrants moved for a diverse range of reasons including cultural motivations and paid employment, a high proportion of gts participants were previously working holiday makers and tourists. the tms recorded that over 60 per cent of respondents moved for work, comparable with international mobil findings and almost 20 per cent more than the gts. tms results, like international mobil, incorporated multiple responses, which makes the lesser stating of non-work-related factors (10% or less) for mobility decisions even more striking. while nearly 25 per cent of german-born current and former residents surveyed in the gts remained in the nt, only 8 per cent of tms respondents chose to remain in the nt after a visit. a mix of work satisfaction and lifestyle, climate and social environment factors appear to make german-born territory migrants ‘stick’ once resident in the nt. in the gts, nearly half (46%) rated work opportunities as something they loved the most about the nt, while ease of obtaining work mattered to only 8 per cent of tms respondents. while the results are not directly comparable, german-born territorians were more worried about the climate (40% versus 26%) and less concerned about remoteness in terms of distance from things (other places, shops, services) than distance from people (family, ageing parents), when compared to respondents to the tms. a recent study of predominantly german-born tourism entrepreneurs and ‘lifestyle migrants’ in remote northern sweden (carson, carson and eimermann 2017) identified comparable key migration drivers to the gts. participants fulfilled their wish for counterurban lifestyles, a better work–life balance, outdoor hobbies and escaping home countries described as ‘too crowded’: ‘a desire to look for a place with more space, fewer people and a quiet environment to enjoy experiences of solitude, peace and personal freedom’ (carson, carson and eimermann 2017 p. 11). gts respondents similarly were often ‘lifestyle migrants’ tired of the big cities who enjoyed the simplicity and low population density of the nt with nature at their doorsteps, space and opportunity for adventure. they described the nt as ‘different’, fulfilling their need for adventure and a counter-urban lifestyle. unique work opportunities and a good work–life balance were also cited as reasons for remaining. german-born territorians appeared stickier (42% had little or no intention of leaving) than respondents to the international mobil study, where around 41 per cent of germans abroad planned to return home and only a third planned to remain overseas (svr 2015 p. 52). while some gts respondents considered a move away from the nt in the future, most of these thought they would stay in australia (68%) rather than returning overseas (12%). hence, although some will inevitably leave, german migrants to the nt are contributing to ‘brain circulation’ through labour mobility (svr 2015 p. 17) and embeddedness in communities. they will continue to benefit the nt, whose strength lies in its multicultural, skilled, resilient population that is committed to local communities, invested in environmental sustainability and empowers the territory through knowledge flows and international connectivity. australian population studies 2 (1) 2018 maertens a and taylor a 49 6. conclusion population challenges for the north of australia are not limited to growth per se, but include longterm structural changes that impact its attractiveness to certain migration markets. moreover, changing technologies and workforce practices for major industries and projects are reducing requirements to locate jobs in situ (taylor and carson 2017) and demographic ageing is seeing relatively large numbers of pre-retirees leave and be replaced with more transient residents. a male dominance continues in the overall population, although this varies according to location. in this context, there are clearly no ‘silver bullet’ levers for governments or industry to turn around population growth rates. the key appears to be in making incremental improvements to population growth through targeting markets within australia and overseas that are more likely to be attracted and retained by the unique lifestyle and opportunities of the north. our study has demonstrated that german-born migrants hold promise as one such international source market and may attract more long-term residents through chain migration. many have stayed, formed relationships and started families in the nt. while the availability of jobs has no doubt played a pivotal role in enabling this, a range of other factors are identified in the study. in a 2016 radio interview, darwin’s german club president ralf scharmann said many germans he knew couldn’t imagine living anywhere else (plitzco 2016). data from the gts shows that german-born nt residents have particular attributes that define their migration patterns, including diverse reasons for arrival and specific career expectations. recruitment efforts may benefit by being focused on these attributes across population groups and job types (carson et al. 2010), as well as collaborating and exchanging knowledge with other peripheral regions across the world such as northern sweden, which may attract similar migrants. there is still ample opportunity to build on existing studies that examine the attraction and retention of migrants. the internet and social media provide powerful new tools for data gathering. gts responses highlight opportunities for recruiting skilled women, in particular, by marketing attractive careers, competitive salaries, employment conditions and career progression opportunities, and adding unique nt selling points to the mix. policymakers should also consider solutions to areas for improvement raised in the gts, such as recognition of education and qualifications and a better support system for newly arrived skilled migrants who lack existing networks. the high number of gts participants who arrived as working holiday makers and tourists and expressed little or no intention of leaving also highlights the importance of tourism as a positive market force and suggests a positive association with permanent migration. finally, as remarked by respondents across the nt, the territory has the advantage of an attractive natural environment, a sunny climate and multicultural, friendly communities. while many immigrants will eventually move interstate or return overseas, these factors will ensure that a substantial number will ‘stick’ around for the long term. key messages • german-born residents are a relatively immobile (‘sticky’), highly educated and female dominated population group in the nt. • factors contributing to the attraction and retention of the german-born market segment may be applicable to other markets: not least ‘lifestyle’, multiculturalism, employment and environment. 50 maertens a and taylor a australian population studies 2 (1) 2018 • the nt’s particular occupational and industry mix seemed well suited to the professional and lifestyle aspirations of female german migrants participating in the gts. • the high number of gts participants who arrived initially in the nt as tourists and expressed little or no intention of leaving, highlights the contribution and importance of the tourism industry to population stabilisation and growth. • this study is an ideal baseline to inform further northern initiatives and policies to progress attraction and retention prospects. acknowledgements the authors would like to thank the many current and former german-born territorians who provided valuable insights in their survey responses and helped recruit other participants with great enthusiasm. danke schön! references abs (australian bureau of statistics) (2017) 2016 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(2016) treffpunkt: deutscher klub darwin. sbs german radio. 1 april. https://www.sbs.com.au/yourlanguage/german/en/audiotrack/treffpunkt-deutscher-klubdarwin. accessed on 7 october 2017. svr gmbh (forschungsbereich beim sachverständigenrat deutscher stiftungen für integration und migration) (2015) international mobil: motive, rahmenbedingungen und folgen der ausund http://www.northernaustralia.gov.au/files/files/nawp-fullreport.pdf http://www.northernaustralia.gov.au/files/files/nawp-fullreport.pdf https://doi.org/10.1080/15022250.2017.1339503 https://www.sbs.com.au/yourlanguage/german/en/audiotrack/treffpunkt-deutscher-klub-darwin https://www.sbs.com.au/yourlanguage/german/en/audiotrack/treffpunkt-deutscher-klub-darwin australian population studies 2 (1) 2018 maertens a and taylor a 51 rückwanderung deutscher staatsbürger. studie des svr-forschungsbereichs, des bundesinstituts für bevölkerungsforschung (bib) und der universität duisburg-essen, gefördert von der stiftung mercator. https://www.svr-migration.de/publikationen/international-mobil/. accessed on 9 august 2017. taylor a (2016) introduction: settlements at the edge. in: taylor a, carson d, ensign p, huskey l, rasmussen r and saxinger g (eds) (2016) settlements at the edge: remote human settlements in developed nations. gloucester, uk: edward elgar; 3–24. taylor a (2018) heading north, staying north? the increasing importance of international migrants to northern and remote australia. migration and border policy working paper, no. 7. the lowy institute for international policy, sydney. https://www.lowyinstitute.org/sites/default/files/documents/taylor%20%20increasing%20importance%20of%20international%20migrants%20to%20northern%20and%2 0remote%20australia_web.pdf. taylor a and carson d (2017) synthesising northern territory population research: a report to the northern territory department of the chief minister. darwin: charles darwin university, northern institute. taylor a, payer h and brokensha h (2015) a demographic profile of international migrants in northern australia. research brief. issue rb06, 2015. darwin: northern institute, charles darwin university. http://www.cdu.edu.au/northern-institute/ni-research-briefs. accessed on 22 february 2018. tourism nt (2017). international visitation to the northern territory: year ending september 2017. http://www.tourismnt.com.au/corporate/research/latest-visitor-data. accessed on 22 february 2018. https://www.svr-migration.de/publikationen/international-mobil/ http://www.cdu.edu.au/northern-institute/ni-research-briefs http://www.tourismnt.com.au/corporate/research/latest-visitor-data australian population studies 2018 | volume 2 | issue 1 | pages 1–13 © markham and biddle 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org recent changes to the indigenous population geography of australia: evidence from the 2016 census francis markham* the australian national university nicholas biddle the australian national university * corresponding author. email: francis.markham@anu.edu.au. address: centre for aboriginal economic policy research, the australian national university, 24 kingsley street, acton, act 2601, australia paper received 15 february 2018; accepted 3 may 2018; published 28 may 2018 abstract background the indigenous population of australia has grown very rapidly since the first tabulation of census statistics about indigenous people in the 1971 abs census of population and housing (census). understanding the size and location of the indigenous australians is important to the state for service delivery and policy, and for indigenous peoples themselves. aims this paper summarises changes to population geography of indigenous australians between 2011 and 2016. it describes the growth in the estimated population, and its changing geographic distribution. the paper derives a measure of ‘unexpected population change’: the spatial mismatch between demographic projections from the 2011 and 2016 census counts. data and methods census data and population projections are tabulated and mapped. results indigenous people now comprise 3.3 per cent of the total australian population, or 798,381 persons. this population grew by 3.5 per cent each year between 2011 and 2016, a rate of growth 34 per cent faster than that explained by natural increase alone. both aspects of growth were concentrated in more urban parts of the country, especially coastal new south wales and southeast queensland. for the first time, fewer than 20 per cent of indigenous people were recorded as living in remote areas. conclusions indigenous population growth continues to be remarkably rapid. future research is required to understand the correlates and causes of population growth beyond that explained by natural increase. key words indigenous population growth; identification change; abs census; indigenous population geography; australia. http://www.australianpopulationstudies.org/ mailto:francis.markham@anu.edu.au 2 markham f and biddle n australian population studies 2 (1) 2018 1. introduction a detailed understanding of the indigenous population in australia is a matter of great interest to policy makers and indigenous peoples. for example, knowledge of the size, composition and characteristics of the indigenous population are used to inform government policy (e.g. the ‘closing the gap’ strategy), service delivery (e.g. the national partnership agreement on remote service delivery), resource allocation (e.g. the state-based redistribution of revenue from the federally levied goods and services tax (gst)) and advocacy for social justice (e.g. calma 2006). tabulations and estimates derived from the australian bureau of statistics (abs) census of population and housing (census) provide the best available information on the size and composition of the indigenous population of australia, albeit imperfectly. consequently, a detailed understanding of indigenous population change between 2011 and 2016 is of value to policy makers, service providers and indigenous peoples. the definition of the ‘indigenous population’ is a contentious one, and the questions in the census have arguably never met the needs of that population itself. indeed, the notion of an ‘indigenous population’ is a colonial construction which has been used to exclude indigenous people and discriminate against them (dodson 2003). for example, one primary imperative for counting the indigenous people in federated australia was the implementation of the nation’s discriminatory constitution which necessitated that indigenous persons be excluded from official population estimates produced for constitutional purposes (arcioni 2012; chesterman and galligan 1997). in practice, this meant that all people who were reached by census collectors were asked to complete a census form that included a question on ‘race’ requiring respondents to state their ‘proportion’ of aboriginal heritage. those who stated that they were ‘more than half’ aboriginal were excluded from most published population statistics (abs 2011). while this constitutional requirement was removed by a federal referendum in 1967, the census has continued to ask australian residents about their indigenous origin and is likely to do so for the foreseeable future. although questions designed to identify indigenous people have been included in every australian census, it has only been since 1971 that indigenous people have been included in the census count. the purpose, wording and administration of census questions designed to identify the indigenous population have changed considerably over time. the 2011 and 2016 census questionnaires asked about each person in the household: ‘is the person of aboriginal or torres strait islander origin?’ respondents were offered the response options of ‘no’, ‘yes, aboriginal’ and ‘yes, torres strait islander’, and were advised ‘for persons of both aboriginal and torres strait islander origin, mark both “yes” boxes’. it is important to note that this ‘standard indigenous question’ does not perfectly capture aboriginal and torres strait islander notions of indigeneity or many administrative definitions of the indigenous population. however, as walter and andersen (2013) insist, recognition of the colonial nature of these categories need not entail the abandonment of statistics about indigenous peoples. rather, they argue for the reframing of statistical collections and their interpretations in a manner that reflects indigenous standpoints. this paper adopts the abs census definition of aboriginal and/or torres strait islander peoples to explore indigenous population change in australia. the purpose of this paper is to provide an overview of the changing size and spatial distribution of the indigenous population of australia, comparing the results of the 2011 and 2016 censuses. the paper summarises three key aspects of the intercensal change: australian population studies 2 (1) 2018 markham f and biddle n 3 • the growth in the estimated population of indigenous australians • the changing geographic distribution of aboriginal and torres strait islander persons • ‘unexpected’ population change, or the spatial mismatch between demographic projections from the 2011 and 2016 census counts. 2. indigenous population increase the indigenous population increased rapidly between 2011 and 2016. in the 2016 census, 590,056 people were counted as aboriginal, 32,345 were counted as torres strait islander and 26,767 were counted as both aboriginal and torres strait islander. combined, 649,171 people were counted as indigenous, an increase of more than 100,000 people, or 18.4 per cent, since 2011. this count of the indigenous population compares with 21,341,231 persons who identified as not being of aboriginal or torres strait islander origin, resulting in the indigenous population making up 3.0 per cent of those who answered the indigenous origin census question, an increase from 2.7 per cent in 2011. the census count underestimates the number of aboriginal and torres strait islander people to a much greater degree than it underestimates the number of other australians. the abs postenumeration survey (pes), which re-interviews around 0.5 per cent of australian households nationally, is used as the basis for producing population estimates (as distinct from population counts tabulated from the census). in 2016, the pes sampled around 800 households from 33 discrete indigenous communities. the indigenous population estimate from the pes attempts to correct for at least three types of census undercount (abs 2017a): • first, a significant proportion of census records do not have a response to the indigenous status question (6.0% in 2016) and some of these individuals are likely to be of aboriginal and torres strait islander origin. records with indigenous status not stated come about either because that particular question was skipped over on the census form or because no census form was received for a dwelling that census collectors deemed to be occupied on census night. in the latter case, census collectors impute the existence of a certain number of residents, but do not answer the indigenous status question for these individuals. • second, some individuals are missed by the census – they simply do not appear on any household’s census form. this could be because they were omitted from a completed census form because census collectors missed their dwelling, or because census collectors mistakenly thought their dwelling was unoccupied. • third, a number of individuals who are listed as not being of aboriginal or torres strait islander origin on the census form later state that they are of aboriginal or torres strait islander origin when asked in the pes several weeks later, a survey that is administered face-to-face to most participants. after the pes is released, the abs further adjusts the population estimate by backdating the censusnight estimate to 30 june and estimating the number of residents temporarily overseas and thus outof-scope for the pes (abs 2017b). based on these adjustments, the abs (2017b) estimate that there were 798,381 aboriginal or torres strait islander australians in august 2016. this population estimate is an increase of 128,000 persons from 2011, or 3.5 per cent per annum. such rapid increase is not unusual for the australian indigenous population. 4 markham f and biddle n australian population studies 2 (1) 2018 as table 1 shows, both the census count and the population estimate of aboriginal and torres strait islander persons have increased considerably in almost every census since the 1967 referendum. while the annualised growth of 3.5 per cent in the aboriginal and torres strait islander population between 2011 and 2016 is substantial, it is less than the mean annual growth from 1971 to 2011 of 4.1 per cent. table 1: census count and population estimates of aboriginal and torres strait islander australians, 1901–2016 year census count population estimate undercount (%)d indigenous persons percentage of total counta,b annual growth rate (%) indigenous personsc percentage of total populationb annual growth rate (%) 2016 649,171 2.8 3.4 786,689 3.3 3.5 17.5 2011 548,370 2.5 3.8 662,335 3.0 5.2 17.2 2006 455,030 2.3 2.1 513,977 2.5 2.2 11.5 2001 410,003 2.2 3.0 460,140 2.4 4.3 10.9 1996 352,970 2.0 5.9 372,052 2.0 5.6 5.1 1991 265,489 1.5 3.1 283,631 1.6 3.4 6.4 1986 227,645 1.4 7.3 240,152 1.4 – 5.2 1981 159,897 1.1 -0.1 – – – – 1976 160,915 1.1 6.8 – – – 1971 115,953 0.9 7.5 150,076 1.1 2.6 22.7 1966e 80,750. 0.7 0.1 132,219 1.1 2.4 38.9 1961 80,526 0.8 3.8 117,495 1.1 2.3 31.5 1954 62,084 0.7 2.8 100,048 1.1 2.0 37.9 1947 51,048 0.7 0.9 87,000 1.1 1.2 41.3 1933 45,066 0.7 1.1 73,828 1.1 -0.2 39.0 1921 39,399 0.7 2.7 75,604 1.4 -1.0 47.9 1911 30,052 0.7 -4.6 83,588 1.8 -1.2 64.0 1901 48,248 1.3 – 94,564 2.4 – 49.0 sources: population estimates for 1901–1971 from abs (1986) and abs (2014a), for 1986 and 1991 from abs (1994), for 1996 from abs (1996) and for 2001–2016 from abs (2017a). census counts for 1911 from cbcs (1917), for 1921 from cbcs (1927), for 1933 from cbcs (1940), for 1947 from cbcs (1952), for 1954 from cbcs (1962), for 1961 from cbcs (1967), for 1966 from cbcs (1971), for 1901–1966 from abs (2014a), for 1971–1991 from abs (2004) and for 1996–2016 from abs community profiles. notes: all pes-derived population estimates displayed above are based on the census of that year. to the best of the authors’ knowledge, the abs did not produce estimates of the indigenous population for censuses between 1966 and 1981. the 1996 pes-derived estimate is based on the estimated population at 30 june, while all other listed figures related to the population on census night in early august. a the denominator of this percentage includes those who did not state their indigenous status in the census. b census counts and population estimates from 1901 to 1966 are for what the abs termed ‘full blood aborigines’, who were counted in the census and excluded from population statistics. because of this exclusion, denominators for these percentages have been counted by adding the indigenous census counts and population estimates to the official non-indigenous figures. persons identified in the pre-1967 censuses as ‘half-caste’ were counted as non-indigenous in these censuses and population estimates. c this column uses pes population estimates where possible (i.e. excluding those residents temporarily absent from australia on census night) in order to consistently calculate the undercount rate. d these undercount rates are calculated consistently using the method from the 2016 pes, and so do not match the published undercount rates from previous years. e excludes torres strait islanders. the indigenous census count – that is, the number of people identified as being of aboriginal or torres strait origin in the census itself, without adjustment for undercount – has also increased substantially, rising from 548,370 in 2011 to 649,171 in 2016. this is consistent with historical trends since the 1967 referendum, with the indigenous census count increasing in every census during that australian population studies 2 (1) 2018 markham f and biddle n 5 period, with the exception of the 1981 census. concerningly, the indigenous undercount rate, or difference between the population estimate and census count, is at the highest level recorded in censuses since the 1980s. the undercount rate has steadily increased from 5.2 per cent in 1986 to 17.5 per cent in 2016. while this partly reflects improvements to the population estimate, it also may indicate an increase in the number of households who have chosen not to participate in the census. the 3.5 per cent annual growth of the indigenous population between 2011 and 2016 outstripped demographic projections of population growth based on the 2011 census by a considerable degree. as figure 1 shows, around 42,000 more indigenous people were identified to be resident in australia in 2016 than the abs had predicted in projections based on the 2011 census. in this figure, the black line represents the estimate of the indigenous population based on the census of that year (i.e. the abs’s indigenous population estimates listed in table 1); the shaded region indicates the range of population estimates for that year produced by the abs based on the immediately previous census. the ‘unexplained growth’ in the indigenous population is illustrated by the gap between the black line and the shaded region. figure 1: aboriginal and torres strait islander population estimates compared with demographic population projections based on the previous census, 1996–2016 source: abs (2014b) for 2006, 2011 and 2016; abs (1998) for 2001 and 1996. notes: the population projections were produced by the abs, based on the immediately previous census (e.g. the 1996 projection is based on the 1991 census, the 2001 projection is based on the 1996 census counts, and so on). the upper bounds of the projections for 2006 and 2001 have been modified to remove predicted unexplained population growth, which was included as a component of those projections only. unexplained growth – estimated here as the difference between the 2011-based 2016 population projection and the 2016-based 2016 population estimate – accounted for around 34 per cent of intercensal population growth between 2011 and 2016. this unexplained growth is likely to result from the changing propensity of people to identify as indigenous in the census and pes, from changing rates of mixed partnering, and from changes to the methods used in administering the census and pes. figure 1 also demonstrates that the gap between the indigenous population estimates and projections based on the previous census has narrowed, compared with the growth in the indigenous population between 2006 and 2011, during which around 59 per cent of growth was unexplained. 6 markham f and biddle n australian population studies 2 (1) 2018 3. a changing spatial distribution while the number of people counted in the censuses as being of aboriginal and/or torres strait islander origin increased by 100,801 between 2011 and 2016, this growth was not evenly distributed across australia. understanding the spatial distribution of the indigenous population is important not only for local service delivery, but for resource distribution. for example, the distribution of the gst to the states and territories is influenced by the proportion of the population who are indigenous. given that the growth of the indigenous population has been most rapid in urban areas (taylor 2013), a continuation of existing trends is likely to result in a shift of the population away from parts of the country where the indigenous population is more likely to live in discrete communities, and more likely to be experiencing extreme economic disadvantage. when examined at the regional level, it is clear that growth in the indigenous census count between 2011 and 2016 is concentrated in the most heavily populated parts of new south wales and queensland. figure 2 maps indigenous population change using the 37 non-administrative indigenous regions defined by the abs, a geography that maps approximately onto the regional geography used by governments to deliver services to indigenous australians. figure 2: change in the number of indigenous people counted in the census by indigenous region, 2011–2016 source: abs 2011 and 2016 censuses. as figure 2 above shows, counts increased the most in the brisbane (17,463 persons), new south wales central and north coast (17,452 persons) and sydney–wollongong (13,852 persons) indigenous australian population studies 2 (1) 2018 markham f and biddle n 7 regions. these regions accounted for almost half of the recorded gross indigenous population growth (47.9%). at the other end of the spectrum, several regions experienced a decline in the number of people counted as being of aboriginal and torres strait islander origin in the 2016 census. declining census counts were of a much smaller magnitude than population growth, with kununurra (745 persons) and alice springs (359 persons) experiencing the largest falls in the number of indigenous people counted in the census. a similar but not identical geographic pattern of growth is apparent when indigenous population change is mapped in terms of percentage growth rather than absolute growth. as figure 3 shows, percentage population growth was high across much of southeastern australia, with the indigenous populations of victoria, tasmania, the australian capital territory, southern and eastern new south wales and southeast queensland all growing by more than 20 per cent between 2011 and 2016. the fastest growing regions were the new south wales central and north coast (33.4%), brisbane (32.8%) and melbourne (34.5%), while population decline was most rapid in kununurra (13.5%) and alice springs (7.2%). figure 3: percentage change in the number of indigenous people counted in the census by indigenous region, 2011–2016 source: abs 2011 and 2016 censuses. while these results might be interpreted as suggesting that the distribution of the indigenous population is becoming more similar to that of the non-indigenous population, the census figures do not tell a simple story of converging geographic distributions. clearly, the less urbanised indigenous population continues the long-term trend of becoming increasingly likely to live in cities. 8 markham f and biddle n australian population studies 2 (1) 2018 as table 2 shows, 36.8 per cent of the indigenous population lived in what the abs terms ‘major cities’ in 2016, an increase of 2.6 per cent from 34.2 per cent in 2011, using a consistent geographic classification. this increase consists of a combination of natural increase, migration and statistical ‘identification change’. identification change occurs when an individual is classified as being of aboriginal or torres strait islander origin in one census but not the following census, or vice versa (biddle and crawford 2015). however, during this same period, the non-indigenous population also became increasingly urbanised, with 72.3 per cent of non-indigenous australians resident in major cities in 2016, an increase of 1.3 per cent from 71.0 per cent in 2011. table 2: the indigenous and non-indigenous population count distributions by geographical remoteness, 2016 remoteness indigenous population count percentage of indigenous count change in percentage of indigenous count, 2011– 2016 nonindigenous population count percentage of nonindigenous population count change in percentage of non-indigenous population count, 2011– 2016 major cities 235,527 36.8 2.6 15,409,691 72.3 1.3 inner regional 154,087 24.1 1.7 3,858,090 18.1 -0.5 outer regional 130,976 20.5 -1.5 1,738,227 8.2 -0.6 remote 40,689 6.4 -1.0 224,485 1.1 -0.1 very remote 79,041 12.3 -1.9 90,897 0.4 -0.1 source: abs 2011 and 2016 censuses. notes: not stated population excluded. calculated on the basis of 2011 remoteness boundaries, using an area-based 2016 to 2011 statistical area level 1 (sa1) concordance. however, the starkest divergence in population dynamics lies in ‘inner regional’ areas, where 24.1 per cent of indigenous people and 18.1 per cent of non-indigenous people now live. while the proportion of the indigenous population living in inner regional areas continues to grow (up 1.7% in 2016 from 2011), the proportion of the non-indigenous population living in these locations fell by 0.5 per cent between 2011 and 2016. another difference between the two populations is that much of the growth of non-indigenous australians in urban areas is likely to be driven by international immigration. for the indigenous population the impact of international migration is negligible, with the small percentage of indigenous australians who move overseas mostly balanced by the small percentage who return. growth in urban areas is therefore likely to be made up of a combination of excess of births over deaths, changing patterns of identification and internal migration. 4. the geography of unexpected population change indigenous population growth between 2011 and 2016 was well above what could be explained by natural increase alone. as described above, the indigenous population in australia on census night, (9 august 2016) was estimated to be 786,689 on the basis of the pes, or 3.3 per cent of the total australian population (table 1). this was around 42,000 more than the upper range of the indigenous population projections based on the 2011 census. this unexplained population growth is likely to arise from identification change, and potentially also from changes to enumeration and processing methods between the 2011 and 2016 censuses. australian population studies 2 (1) 2018 markham f and biddle n 9 there is little reason to expect that the unexplained population growth is distributed evenly across australia. although too little information has been published at present to construct detailed regional population estimates, including age–sex distributions, provisional estimates can be derived using a simple, three-step procedure, as described below. • first, those records with no response to the indigenous origin question had their indigenous status imputed on the basis of the percentage of respondents who identified as indigenous in their statistical area level 1 (sa1). this increased the indigenous population from a count of 643,136 (excluding those in migratory, shipping and offshore areas) to an estimate of 692,182. • second, a provisional population estimate for each region was derived by multiplying these regional, prorated indigenous population estimates by 1.137. this multiplier was selected so that the sum of all regional population estimates equalled 786,689, the national estimate derived from the pes. • third, indigenous population projections for each region for 2016, based on the 2011 census, were subtracted from provisional population estimates for regions. the 2011-based projections were produced on the basis of natural increase and a repetition of 2006–2011 migration patterns. (for more detail, see biddle 2013.) consequently, the subtraction of the 2011-based projection from the 2016-based estimate gives a measure of unexpected population change for each region, or the spatial mismatch between projected and observed population increase. because some of this population change will be explained by changing migration patterns between 2011 and 2016, we term this population change ‘unexpected’ rather than ‘unexplained’. figure 4: unexpected population change by indigenous region, 2011–2016 source: authors’ estimates based on abs 2011 and 2016 censuses. 10 markham f and biddle n australian population studies 2 (1) 2018 estimates of unexpected population change by indigenous regions are displayed in figure 4 (above). put simply, the figure shows the difference between the estimated indigenous population in 2016, and the expected 2016 indigenous population, as projected on the basis of the 2011 census by biddle (2013). because the total indigenous population increased faster than projected, the unexpected population change in most regions was positive (i.e. the indigenous population increased faster than anticipated). however, in 10 of the 37 regions, unexpected population change was negative, meaning that the indigenous population increased less quickly than projected. much of the unexpected population increase occurred in south-eastern australia. in particular, more than 75 per cent of the unexpected population increase occurred in just five regions: new south wales central and north coast (14,844); sydney–wollongong (7,412); brisbane (5,813); riverina– orange (4,713); and northeastern new south wales (3,600). while these regions were projected to experience substantial population increase, the actual population increase substantially exceeded expectations. however, not all regions saw greater than expected population growth between 2011 and 2016. for example, the sixth most rapidly growing region, townsville–mackay, had an estimated indigenous population increase of 4,800 persons, very close to the projected increase of 4,600. other regions experienced population changes that were substantially less than projected. for example, the indigenous population of perth was projected to increase by 5,628 between 2011 and 2016, but instead grew by only 1,734 persons. similarly, the indigenous population of alice springs was projected to increase by 817 persons, but our estimates suggest that it decreased by 745 persons. 5. conclusions the quinquennial abs census remains the best source of information on indigenous population change. the aim of this paper was to provide an overview of the changing size and spatial distribution of the indigenous population of australia between 2011 and 2016, with a focus on the geography of unexpected population change. the first set of analyses focused on the growth in the estimated population of indigenous australians. we showed that the indigenous population grew rapidly between 2011 and 2016, reaching around 3.3 per cent of the total population estimate, or 786,689 persons. it is more than just a historical footnote to reflect upon the fact that this is similar to the accepted population estimate of the indigenous population at the time of european colonisation (mulvaney 2002), up from a low of around 72,000 at the time of the 1921 census (which is likely to have been a significant undercount). like other indigenous groups internationally (in particular, the united states, canada and new zealand), the indigenous population has rebounded substantially from the destruction wrought by frontier violence, disease and other forms of colonial domination. the geographic distribution of the indigenous population is also changing. between 2011 and 2016, the most rapid growth in the indigenous population count occurred in more urban parts of the country, with three regions (brisbane, the new south wales central and north coast and sydney– wollongong) accounting for almost half of the recorded gross indigenous population growth. there continues to be a policy focus on indigenous australians living in remote areas. the results of this paper suggest that a remote focus is becoming less justifiable on the basis of population geography alone, as the remote indigenous population continues to shrink as a percentage of the total australian indigenous population. australian population studies 2 (1) 2018 markham f and biddle n 11 as the economic circumstances of the remote and urban indigenous population appear to be diverging, at least when measured in terms of income (markham and biddle 2018), the spatially uneven indigenous population increase suggests that resource targeting within the indigenous population may need to become a more prominent policy consideration. indeed, while indigenous disadvantage may be most concentrated in remote areas, in absolute terms there are more disadvantaged individuals living in urban areas. consequently, it is important that regional approaches to policy do not ignore intra-regional indigenous inequality. considerable uncertainty exists regarding the growth in the population that cannot be explained by the excess of births over deaths. by comparing the 2016 census data with population projections based on 2011 data, we have shown that unexplained indigenous population growth accounts for around 34 per cent of total intercensal population growth. while considerable, this proportion is less than the equivalent for the 2011 census, for which around 59 per cent of intercensal growth was unexplained. much of this excess or unexplained growth is likely to be caused by people changing their response in successive censuses to the indigenous ‘origin’ question, or by their indigenous identification being given differently by those who respond to the census on their behalf (see biddle and markham 2018). previous research has shown that many indigenous australians are selective about the contexts in which they reveal their aboriginal or torres strait islander origin. this research suggests that the propensity for an individual to identify themselves as aboriginal often depends on their assessment of the risks and benefits of doing so, particularly with respect to racism and discrimination and whether or not identification would lead to a challenge to prove aboriginal identity (abs 2013; biddle and crawford 2015; nsw aboriginal affairs 2015). while this contextualisation is crucial to understanding identification, further research is needed to understand the causes of spatial variation in identification change, and the likelihood of continued identification change into the future. indeed, our research demonstrates that the unexplained growth in indigenous counts is neither spatially nor demographically consistent. while much of this growth occurred in three urban regions (sydney–wollongong, nsw north and central coast, and brisbane), however there were also large urban regions like perth where the population increased more slowly than expected from the population projections. further research into the components of intercensal population growth would assist in understanding the social and demographic drivers of indigenous population change. 6. key messages • 81.4 per cent of the indigenous population now live in urban or regional areas. • the indigenous population grew between 2011 and 2016 at a rate of 3.5 per cent per year, to an estimated population of 798,381. • the intercensal population increase of 128,000 persons is around 42,000 persons (or 34%) greater than can be accounted for by natural increase. this is likely to result from the changing propensity of individuals to identify as indigenous in the census or changes to the census collection and processing methods. • indigenous population growth was highest in coastal regions between melbourne and brisbane, while the indigenous population of several remote regions australia fell modestly. • identification change is very spatially concentrated, and is most rapid in tasmania, new south wales and brisbane. 12 markham f and biddle n australian population studies 2 (1) 2018 acknowledgements this manuscript is based on research funded by the australian government department of the prime minister and cabinet. all opinions expressed in the paper and any errors made therein are attributable to the authors alone. references abs (australian bureau of statistics) (1986) australian demographic trends. cat. no. 3102.0. canberra: abs. abs (1994) experimental estimates of the aboriginal and torres strait islander population, june 1986 to june 1991. cat. no. 3230.0. canberra: abs. abs (1996) australian demographic statistics. cat. no. 3101.0, march, june, september and december. canberra: abs. abs (1998) experimental projections of the aboriginal and torres strait islander population, 1996 to 2006. cat. no. 3231.0. canberra: abs. abs (2004) year book australia. cat. no. 1301.0. canberra: abs. abs (2011) reflecting a nation: stories from the 2011 census, july 2011. cat. no. 2071.0. canberra: abs. abs (2013) information paper: perspectives on aboriginal and torres strait islander identification in selected data collection contexts, 2012. cat. no. 4726.0. canberra: abs. abs (2014a) australian historical population statistics. cat. no. 3105.0.65.001. canberra: abs. abs (2014b) estimates and projections, aboriginal and torres strait islander australians, 2001 to 2026. cat. no. 3238.0. canberra: abs. abs (2017a) census of population and housing: details of overcount and undercount, australia, 2016. cat. no. 2940.0. canberra: abs. abs (2017b). australian demographic statistics, mar 2017. cat no. 3101.0. canberra: abs. arcioni e (2012) excluding indigenous australians from ‘the people’: a reconsideration of sections 25 and 127 of the constitution. federal law review 40(3): 287–316. biddle n (2013) population projections. caepr indigenous population project: 2011 census papers, paper 14, centre for aboriginal economic policy research, australian national university, canberra. biddle n and crawford h (2015) the changing aboriginal and torres strait islander population: evidence from the 2006–11 australian census longitudinal dataset. caepr indigenous population project: 2011 census papers, paper 18. centre for aboriginal economic policy research, australian national university, canberra. biddle n and markham f (2018) indigenous identification between 2011 and 2016: evidence from the australian census longitudinal dataset. caepr topical issue 1/2018. centre for aboriginal economic policy research, australian national university, canberra. calma t (2006) social justice and human rights: using indigenous socioeconomic data in policy development. in: hunter b (ed.), assessing the evidence on indigenous socioeconomic outcomes. canberra: anu press; 299–310, http://press.anu.edu.au?p=119431. cbcs (commonwealth bureau of census and statistics, australia) (1917). census of the commonwealth of australia, 1911. abs cat. no. 2112.0. melbourne: cbcs. cbcs (1927) census of the commonwealth of australia, 1921. abs cat. no. 2111.0. melbourne: cbcs. cbcs (1940) census of the commonwealth of australia, 1933. abs cat. no. 2110.0. canberra: cbcs. cbcs (1952. census of the commonwealth of australia, 1947, abs cat. no. 2109.0. canberra: cbcs. cbcs (1962) census of the commonwealth of australia, 1954, abs cat. no. 2108.0 canberra: cbcs. cbcs (1967) census of the commonwealth of australia, 1961, abs cat. no. 2107.0 canberra: cbcs. http://press.anu.edu.au/?p=119431 australian population studies 2 (1) 2018 markham f and biddle n 13 cbcs (1971) census of population and housing, 1966. abs cat. no. 2106.0. canberra: cbcs. chesterman j and galligan b (1997) citizens without rights: aborigines and australian citizenship. cambridge: cambridge university press. dodson m (2003) the end in the beginning: re(de)finding aboriginality. in: grossman m (ed.) blacklines: contemporary critical writing by indigenous australians. melbourne: melbourne university press; 25–42. markham, f and biddle n (2018) income, poverty and inequality. caepr indigenous population project: 2016 census papers, paper no. 2, centre for aboriginal economic policy research, australian national university, canberra. mulvaney j (2002) ‘difficult to found an opinion’: 1788 aboriginal population estimates. in: briscoe g and smith l (eds), the aboriginal population revisited: 70 000 years to the present. canberra: aboriginal history inc.; 1–8. nsw aboriginal affairs (2015) aboriginal identification in nsw: the way forward. an aboriginal peoples’ perspective. sydney: nsw aboriginal affairs, department of education. taylor j (2013) indigenous urbanization in australia: patterns and processes of ethnogenesis. in: peters e and andersen c (eds) indigenous in the city: contemporary identities and cultural innovation. vancouver: ubc press; 237–255. walter m and andersen c (2013) indigenous statistics: a quantitative research methodology. walnut creek, california: left coast press. australian population studies 2018 | volume 2 | issue 1 | pages 26–38 © wilson and shalley 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org estimates of australia’s non-heterosexual population tom wilson* charles darwin university fiona shalley charles darwin university * corresponding author. email: tom.wilson@cdu.edu.au. address: northern institute, charles darwin university, ellengowan drive, darwin, nt 0909 paper received 14 february 2018; accepted 28 april 2018; published 28 may 2018 abstract background demographers have studied minority populations for many years, but relatively little attention has been paid to sexual minority groups. population estimates for sexual minorities would be useful as denominators for a range of health and socioeconomic indicators, to monitor representation in employment, assist budget planning and inform the marketing of goods and services. aim the aim of this paper is to present some approximate estimates of the non-heterosexual adult population of australia in mid-2016 by sex, broad age group and state and territory. data and methods data on sexual identity were sourced from three nationally representative surveys: the household income and labour dynamics in australia survey, the second australian study of health and relationships and the abs general social survey. use was made also of 2016 abs census of population and housing (census) data and estimated resident populations. prevalence rates of the non-heterosexual population aged 18+ were averaged over the three surveys and multiplied by erp to obtain national population estimates. census data on same-sex couples were used to distribute the national estimates by state and territory. results australia’s non-heterosexual population aged 18+ in 2016 is estimated to have been 592,000, representing about 3.2% of the adult population. new south wales is home to the largest nonheterosexual population (about 204,000) and the northern territory the smallest (4,700), while the highest prevalence is in the australian capital territory (5.1%). conclusions australia’s non-heterosexual population is a relatively small population, but its prevalence varies considerably by age and sex and between states and territories. estimates of this population should prove useful for monitoring health and wellbeing and for a variety of planning and policy purposes. key words population estimates; non-heterosexual; lesbian, gay, bisexual; states and territories; australia. http://www.australianpopulationstudies.org/ mailto:tom.wilson@cdu.edu.au australian population studies 2 (1) 2018 wilson t and shalley f 27 1. introduction minority populations have been the subject of demographic research and policy development for many decades, particularly ethnic minority populations (e.g. coleman and salt 1996; jivraj and simpson 2015) and indigenous peoples (e.g. smith 1980; taylor 2011). attention has also been paid to groups such as foreign-born populations (e.g. edmonston 2016) and minority religious populations (e.g. peach 2006; pew research center 2017). over the last two decades, and especially in recent years, demographers and statisticians have started to examine sexual and gender minority populations in western countries (e.g. aspinall 2009; baumle, compton and poston 2009; baumle 2013; black et al. 2000; ons 2010; meier and labuski 2013; ons 2017). in australia, the non-heterosexual1 population was subject to increased attention in the lead-up to the australian marriage law postal survey in 2017. following public debate about same-sex marriage over many years, the australian government decided to put the issue to the electorate in late 2017. effectively a plebiscite, the survey asked: ‘should the law be changed to allow same-sex couples to marry?’ of those who returned their forms (and excluding unclear responses), 62 per cent voted ‘yes’ (abs 2017a). shortly afterwards parliament voted overwhelmingly to amend the commonwealth marriage act 1961, and the updated law came into force in december 2017. yet while progress such as this is made towards equality for non-heterosexual people in australia, relatively little is known about the demography of this population. more demographic research could increase knowledge and understanding of this segment of society, leaving less room for stereotypes and myths (gates 2012). better demographic evidence could highlight where disadvantage and discrimination remain, and where policy and legislation need revision. sexual minority population estimates specifically could prove valuable for a variety of health, social justice and economic purposes. for example, estimates could be used to monitor representation in employment, assist budget planning for specific services for sexual minorities, form denominators for a range of health and socioeconomic indicators, and inform the marketing of goods and services (e.g. same-sex weddings). in addition, sexual minority demography can prove useful in broader analyses of demographic trends and theory, such as the influence of gender roles within couples on the labour market consequences of migration (e.g. cooke 2005). the bulk of existing research on sexual minority demography focuses on the united states and, to a lesser extent, the united kingdom (e.g. black et al. 2000; black et al. 2002; cooke and rapino 2007; flores et al. 2016; gates 2014; geary et al. 2018; ons 2017; van kampen et al. 2017). australian research in the area is limited, though a small number of contributions have been made over the last two decades (e.g. dempsey 2015; grulich et al. 2003; madeddu et al. 2006; perales and baxter 2018; prestage et al. 2008; richters, altman et al. 2014; smith et al. 2003; wilson 2004). many australianbased papers are concerned primarily with important sexual health issues, and only a few present population estimates. prestage et al. (2008) estimated the population of gay and bisexual men in australia in each of the states and territories in 2001, while madeddu et al. (2006) created estimates of gay and bisexual men across inner sydney postcodes in 2001. both multiplied gay and bisexual prevalence rates by census counts, using data from the australian bureau of statistics (abs) census 1 we use the term ‘non-heterosexual’ here, but acknowledge there is no standard terminology for sexual and gender minority groups. we discuss this issue in section 2 of the paper. 28 wilson t and shalley f australian population studies 2 (1) 2018 of population and housing (census), to obtain estimates. several other studies included estimates of the prevalence of the non-heterosexual population or parts of it (primarily gay and bisexual men). we argue that there is a need for sexual minority population estimates for australia. ideally, these would be current, available annually, contain age, sex and geographic detail, cover the whole nonheterosexual population but also include separate estimates for lesbian, gay, bisexual and other minority sexual orientations. preferably, the estimates would use estimated resident populations (erps) in their calculation rather than census counts, which suffer from undercount (particularly in the young adult ages). but creating sexual minority estimates is far from straightforward. there are so few demographic data sources which include sexual orientation (wooden 2014), and those that do so have several limitations. defining who should be included in the non-heterosexual population is also complicated because of the complex nature of sexual orientation. the aim of this paper is to present some approximate estimates of the non-heterosexual adult population of australia in mid-2016 by sex, broad age group and state and territory. the estimates are approximate in the sense that they are constructed from several imperfect data sources and necessarily involve several assumptions. at this stage we present state and territory and national estimates only, as well as those for the non-heterosexual population as a whole. finer geographical detail, annual numbers, alternative definitions (see section 2), and separate estimates for lesbian, gay, bisexual and other minority sub-populations are planned in subsequent work. following this introduction we consider how sexual orientation is conceptualised and the issue of appropriate definitions and terminology for sexual minority populations. section 3 describes the data sources and population estimation methods, while section 4 presents the results. a final section includes a short discussion and conclusion. 2. definitions and terminology sexual orientation has been defined as: an enduring pattern of emotional, romantic, and/or sexual attractions to men, women, or both sexes … [and] a person’s sense of identity based on those attractions, related behaviors, and membership in a community of others who share those attractions. (american psychological association 2008 p. 1) it is generally considered to comprise three elements (durso and gates 2013): (i) sexual attraction – the feeling of sexual desire towards others, considered by some to be the fundamental basis of sexual orientation (ii) sexual behaviour – sexual activity (iii) sexual identity – how a person describes their sexual orientation (e.g. heterosexual, gay, lesbian, bisexual). the non-heterosexual population referred to in this paper includes all those who identify as gay, homosexual, lesbian or bisexual, or construct their sexuality in other ways using non-heterosexual terminology (e.g. queer). our focus here is on sexual identity rather than behaviour or attraction. the sexual identity, behaviour and attraction of individuals are not necessarily coterminous. the venn diagram in figure 1 illustrates the relationship between the three dimensions of sexual australian population studies 2 (1) 2018 wilson t and shalley f 29 orientation for the non-heterosexual population. several surveys have found that a relatively large group of people have felt some same-sex sexual desire at some point in their adult lives; a smaller but not wholly overlapping group have engaged in same-sex sexual activity’ and a smaller group still identifies as being non-heterosexual (e.g. geary et al. 2018; richters, altman et al. 2014; smith et al. 2003). identity is shown in the diagram as ‘current’ identity because some people change the way they describe themselves over time. figure 1: the relationship between the three dimensions of sexual orientation source: loosely based on figure 1 in richters, altman et al. (2014) and figure 2 in geary et al. (2018). it is important to recognise that people counted as non-heterosexual in data sources are only those willing to identify as such in statistical collections. strictly, this is the revealed non-heterosexual population. others may consider themselves to be gay, lesbian, bisexual or other in private, but choose not to disclose their sexuality in public. this is the hidden (or ‘closeted’) population, and is not included in our population estimates (see gates 2012 for a discussion of the issue). in addition, it is important to note that sexual orientation is distinct from gender identity and intersex issues, although they are often considered together – for example, in the term lgbtqi (lesbian, gay, bisexual, transgender, queer and intersex). gender identity refers to ‘a person’s innate, deeply-felt psychological identification as a man, woman, or something else’ (fenway health 2010 p. 3). the transgender population consists of those whose gender identity or expression differs from their birth sex, while intersex refers to ‘a spectrum of conditions involving anomalies of the sex chromosomes, gonads, reproductive ducts, and/or genitalia’ (fenway health 2010 p. 9). transgender and intersex populations may be of any sexual orientation. finally, on the issue of terminology, we acknowledge that many different terms are used in the literature covering different population sub-groups, with no single term being standard (dempsey 2015). these include lgb (lesbian, gay and bisexual), lgbt (lesbian, gay, bisexual and transgender), lgbtiq (lesbian, gay, bisexual, transgender, intersex and queer), and lgbtqqip2saa (lesbian, gay, bisexual, transgender, queer, questioning, intersex, pansexual, 2-spirited, asexual and allies). we choose the shorthand term ‘non-heterosexual’ to refer to gay, lesbian, bisexual and related sexual any lifetime samesex behaviour any lifetime samesex attraction current nonheterosexual identity 30 wilson t and shalley f australian population studies 2 (1) 2018 minorities. gender minorities such as the transgender population, and sex minorities such as intersex people, are included in our population estimates only if they have identified as non-heterosexual. 3. data and methods 3.1 data sources data on people identifying as non-heterosexual were acquired from three representative national surveys: the household income and labour dynamics in australia (hilda) survey, the second australian study of health and relationships (ashr2), and the abs general social survey (gss). unpublished data on the population identifying as non-heterosexual by sex and broad age group (18–24, 25–34, 35–44, 45–54, 55–64 and 65+) were obtained and non-heterosexual proportions of the population (or prevalence) calculated for each dataset. the hilda survey is a nationally representative household-based longitudinal survey on the lives of australians (wilkins 2017). it covers a wide range of topics including family relationships, employment, education, income, health and wellbeing, life events and personal attitudes. it is conducted annually by interview and self-completion questionnaire with all those aged 15 years and over in the participating household. a question on sexual identity was included in wave 12 (2012) as part of the self-completion questionnaire (wilkins 2015; wooden 2014). in this wave interviews were conducted with 17,476 respondents and self-completion questionnaires were received from 88 per cent of the interviewed sample. the sexual identity question asked: ‘which of the following categories best describes how you think of yourself? heterosexual or straight; gay or lesbian; bisexual; other; unsure/don’t know; and prefer not to say’ (melbourne institute 2012). the ashr2 was undertaken in 2012 and 2013 to study the sexual and reproductive health, sexual practices and wellbeing of the australian population (richters, badcock et al. 2014). the survey was conducted via telephone interview using random digit dialling of landline and mobile phones. the survey covered australian residents aged 16–69 and obtained responses from 20,094 participants, achieving a response rate of 66 per cent of eligible people contacted. the sexual identity question asked: ‘do you think of yourself as: 1. heterosexual or straight; 2. homosexual (gay [asked of males]; lesbian [asked of females]); 3. bisexual’. other responses were coded as: 4. queer; 5. not sure; undecided; 6. something else/other (richters, altman et al. 2014). the gss is a household-based survey run by the abs every four years. the aim of the survey is to provide a broad range of information on an individual’s social circumstances and their relative levels of advantage and disadvantage (abs 2015a). the survey covers all people aged 15 years and over who are usual residents of private dwellings and is conducted by face-to-face interview. in the 2014 survey 12,932 out of 16,145 eligible persons responded to the survey, representing a response rate of 80 per cent. a question on sexual identity was introduced for the first time in 2014 and was asked of all participants aged 18 years and over. it asked: ‘which of the following options best describes how you think of yourself? 1. straight (heterosexual); 2. gay or lesbian; 3. bisexual; 4. other; 5. don’t know’ (abs 2015b). in addition, our study made use of some data from the 2016 census. counts of persons in same-sex couples by broad age group, sex and state and territory were extracted from the abs tablebuilder australian population studies 2 (1) 2018 wilson t and shalley f 31 pro online data service (abs 2017b). a direct question on sexual orientation is not asked in the australian census. instead, a same-sex couple variable is created by combining information from two census questions: the question on the relationship of an individual in the household to person 1 on the census form; and the question ‘is this person male or female?’. if the relationship of someone to person 1 is recorded as husband or wife or de facto partner, and both individuals record the same answer to the question on gender, then a same-sex couple is identified (abs 2018). nationally, 2016 census counts of individuals aged 18 and over living together as part of a same-sex couple totalled about 90,000 (only 0.5 per cent of adults counted in the census). this is only a subset of all non-heterosexual people, of course. aside from census undercount, non-heterosexual people who are single or in livingapart-together relationships are excluded from the census count of individuals in same-sex couples. hilda survey findings from 2012 show that, amongst those aged 25–59, only 55 per cent of nonheterosexual men and 59 per cent of women are partnered, compared to 74 per cent of heterosexual men and women in that age range (wilkins 2015). in addition, people in cohabiting same-sex couples are not always identified in the census as being in a same-sex relationship: for example, when neither is person 1 on the census form, or if they do not wish to reveal their relationship. furthermore, there is probably some error in the same-sex couple counts due to errors in responses to the question on gender. research in the united states has revealed this to be a problem with their same-sex couple census data (e.g. gates 2010; dibennardo and gates 2014), but there is no information as to whether equivalent response errors have affected australian census data. finally, mid-2016 erps by broad age group, sex and state and territory were obtained from the abs.stat online data extraction tool (abs 2017c). 3.2 methods estimates of the adult non-heterosexual population of australia in 2016 were created by multiplying non-heterosexual proportions averaged across the three surveys (hilda, ashr2, gss) by erps published by the abs for 30 june 2016. the estimates were prepared by sex and broad age group (18–24, 25–34, 35–44, 45–54, 55–64 and 65+) for australia and each of the states and territories. the decision to use proportions averaged across the three surveys was taken because of the non-trivial variations in proportions between surveys and no clear evidence that one survey was superior to another. national estimates were calculated by multiplying averaged proportions by erps: 𝑃𝐴𝑢𝑠,𝑠,𝐴 𝑁𝐻 = 𝑝𝑟𝑜𝑝𝐴𝑢𝑠,𝑠,𝐴 𝑁𝐻 𝐸𝑅𝑃𝐴𝑢𝑠,𝑠,𝐴 (1) where 𝑃 denotes population estimate, 𝐴𝑢𝑠 australia, 𝑝𝑟𝑜𝑝 the proportion of the population, 𝑁𝐻 non-heterosexual, 𝐸𝑅𝑃 estimated resident population, 𝑠 sex and 𝐴 broad age group. state and territory estimates were created by distributing national estimates according to the number of individuals in same-sex relationships identified in the 2016 census: 𝑃𝑖,𝑠,𝐴 𝑁𝐻 = 𝑃𝐴𝑢𝑠,𝑠,𝐴 𝑁𝐻 𝐶𝑖,𝑠,𝐴 𝑆𝑆𝑅 𝐶𝐴𝑢𝑠,𝑠,𝐴 𝑆𝑆𝑅 (2) where 𝑖 denotes state or territory, 𝐶 census counts, and 𝑆𝑆𝑅 the population in same-sex relationships. while the census same-sex couple data provide an imperfect geographical distribution proxy, they do not suffer from small sample size. survey estimates of state and territory non-heterosexual 32 wilson t and shalley f australian population studies 2 (1) 2018 populations were based on samples too small to be of use (e.g. there were zero non-heterosexual males in the northern territory in the hilda data). clearly, the above methods incorporate a number of assumptions which are unlikely to hold precisely. no adjustments have been made for net undercount in the census. it is assumed that the average proportions across the three surveys provide an accurate measure of the identified nonheterosexual population of australia. it is also presumed that the proportion of the population identifying with non-heterosexual identities remains unchanged between the time of the surveys in 2012 to 2014 and mid-2016. for the state and territory population estimates, the distribution of people in same-sex relationships recorded by the 2016 census is assumed to match the distribution of the wider non-heterosexual population. this last assumption is probably the most approximate. it effectively assumes that, for each age-sex group, the proportion of the non-heterosexual population in a same-sex relationship as identified by the census is the same in each state and territory. this is unlikely to be exactly the case, though we note that the census distribution of all persons in couples (irrespective of gender composition) by state and territory and broad age group is extremely close to the equivalent erp distribution. however, variations from our assumption are likely to occur due to educational composition. using survey data from california, carpenter and gates (2008) found that highly educated gay men and lesbian women were more likely to be partnered than those who were less educated. 4. non-heterosexual population estimates 4.1 new estimates the extent to which the australian population identifies as non-heterosexual, using the averaged findings from the three surveys, is shown in table 1 below. amongst the adult population of australia, 3.1 per cent of males and 3.4 per cent of females describe themselves as non-heterosexual. these percentages exclude survey participants who refused to answer the sexual identity question or who replied ‘don’t know’. the percentages are higher at younger ages and lower at older ages, with the age gradient being more pronounced for females. table 1: percentage of the australian adult population identifying as non-heterosexual averaged across three surveys, 2012–2014 age group males females 18–24 4.0 6.4 25–34 4.0 4.8 35–44 3.0 3.8 45–54 2.6 2.6 55–64 2.4 2.0 65+ 2.3 1.1 18+ 3.1 3.4 sources: gss 2014; ashr2; hilda wave 12. estimates of australia’s non-heterosexual population by age group and sex are presented in table 2. they suggest that the national non-heterosexual population aged 18+ in mid-2016 was a little under australian population studies 2 (1) 2018 wilson t and shalley f 33 600,000, representing 3.2 per cent of the total adult population. the figures indicate there were more non-heterosexual females than males in the younger adult ages, with the situation reversed in the older age groups. overall, at ages 18 and above the non-heterosexual population is younger than the australian population as a whole. table 2: estimates of the australian adult population identifying as non-heterosexual, 2016 age group males females persons 18–24 47,098 71,839 118,937 25–34 71,804 86,551 158,355 35–44 48,874 61,770 110,644 45–54 40,848 41,009 81,857 55–64 32,579 28,684 61,263 65+ 39,848 21,011 60,859 18+ 281,052 310,863 591,915 source: authors’ estimates. population estimates for the states and territories are shown in table 3. not surprisingly the most populous states, new south wales, victoria and queensland, are home to the largest non-heterosexual populations, while the australian capital territory (act), tasmania and the northern territory have the smallest populations. all jurisdictions have more females than males in their non-heterosexual populations with the one exception of new south wales. as a fraction of the total population, south australia, western australia and the northern territory have the smallest percentages identifying as non-heterosexual. the act has a relatively large non-heterosexual population at 5.1 per cent of its total adult population, a function to some extent of its comparatively young population (wilson 2016). table 3: estimates of the adult population identifying as non-heterosexual by state and territory, 2016 state/territory population aged 18+ % of erp males females persons persons nsw 106,400 98,023 204,423 3.4 vic 76,267 80,790 157,057 3.3 qld 48,996 63,596 112,592 3.0 sa 14,265 20,818 35,083 2.6 wa 21,280 29,828 51,108 2.6 tas 4,992 5,953 10,945 2.7 nt 2,147 2,596 4,743 2.6 act 6,705 9,258 15,964 5.1 australia 281,052 310,863 591,915 3.2 source: authors’ estimates. notes: nsw = new south wales; vic = victoria; qld = queensland; sa = south australia; wa = western australia; tas = tasmania; nt = northern territory; act = australian capital territory. 4.2 comparisons with other studies comparing our non-heterosexual population estimates with estimates produced by others is not straightforward because of variations in population coverage, reference dates, age ranges, data sources and social and cultural contexts. nonetheless, it is instructive to compare our figures with the few earlier estimates prepared for australia. 34 wilson t and shalley f australian population studies 2 (1) 2018 the gay and bisexual male population aged 16+ was estimated by prestage et al. (2008) to be 182,624 in 2001, representing 2.5 per cent of the male population. the prevalence estimates across states and territories varied from 0.8 per cent for tasmania and 0.9 per cent for the northern territory to 2.9 per cent for the act and 3.0 per cent for sydney. those numbers were based on the first australian survey of health and relationships (ashr). our non-heterosexual population prevalence rates for just the male population aged 18+ varied from a low of 2.2 per cent in south australia and western australia and 2.3 per cent in the northern territory up to 3.6 per cent in new south wales and 4.4 per cent in the act. it was 3.1 per cent for australia as a whole. how do our estimates compare to those produced for other countries? gates (2011) estimated that about 8 million adults identify as lesbian, gay or bisexual in the united states, representing about 3.5 per cent of the adult population. geary et al. (2018) estimated 1.2 million people aged 16–74 in britain identified as lesbian, gay, bisexual or other in 2011, or 2.7 per cent of the population. a recent estimate by the office for national statistics put the population aged 16 and over describing themselves as lesbian, gay, bisexual or other in the united kingdom in 2016 to be 1.3 million, representing 2.5 per cent of the population (ons 2017). in canada, the canadian community health survey found that 3.0 per cent of adults aged 18–59 reported themselves to be lesbian, gay or bisexual in 2014 (statistics canada 2017). in terms of age distributions, our data are consistent with most other studies, which have found a higher prevalence of non-heterosexual identities at younger ages (e.g. gates 2014; ons 2017). however, this is not a universal finding, with the prevalence estimates for britain presented by geary et al. (2018) showing little difference for ages between 16 and 64. overall, our non-heterosexual population estimates are reasonably consistent with other respectable studies, and consist of plausible and sensible numbers. 5. conclusions this paper has presented a novel set of population estimates for australia’s non-heterosexual population, with disaggregation by sex, broad age group and state and territory. the estimates should be regarded as approximate given the limitations of the data sources and the assumptions inherent in our methods. nonetheless, they provide a useful overview of the current nonheterosexual population of australia which was not previously available. it is emphasised that, conceptually, these estimates refer to the population identifying as gay, lesbian, bisexual and in other non-heterosexual ways, and not those who engage in same-sex sexual behaviour or who have ever experienced same-sex sexual attraction (figure 1). population estimates based on these alternative definitions should be useful for health surveillance and will be the subject of subsequent research. ideally, state and territory and sub-state, non-heterosexual population estimates would be based on census or large-scale survey data. the office for national statistics in the united kingdom asks a sexual identity question in its annual population survey, which is sufficiently large (covering 41,000 households each quarter) to enable sexual identity population estimates to be produced for local authorities (ons 2017). perhaps at some point the abs will follow suit and include a direct sexual identity question in a large-scale survey (or even the census). in the meantime it would be useful to investigate alternative data sources for estimating the state and territory distributions because the use of same-sex couple data from the census is imperfect. australian population studies 2 (1) 2018 wilson t and shalley f 35 it is possible that our act prevalence is marginally over-estimated due to its highly educated population. there is likely to be a higher proportion of non-heterosexual people in the act in samesex cohabiting relationships than in other jurisdictions (carpenter and gates 2008), which violates the assumption of a fixed ratio between the number of people in same-sex couples in the census and the non-heterosexual population across jurisdictions. data on the proportion of non-heterosexual adults in same-sex relationships would be ideal as it would enable census counts of persons in samesex couples to be more accurately scaled up to the total non-heterosexual population. it would also be useful to investigate the potential of new web-based data sources, such as google search data and social media profiles. for example, some facebook users reveal sexual orientation on their profiles, but even when they do not, facebook ‘likes’ can be used to accurately predict sexual orientation in 88 per cent of cases (kosinski, stillwell and graepel 2013). in a more controversial paper, wang and kosinski (2018) applied neural networks to detect sexual orientation indirectly from photographs of faces on facebook profiles. clearly, approaches such as these raise some challenging ethical questions, and also questions about data reliability and representativeness. future research should explore these new data sources while also continuing to rely on the strengths of existing survey and census data. key messages • sexual minority population estimates are useful for a variety of health, social justice and economic purposes, and for broader analyses of demographic trends and theory. • australia’s non-heterosexual population aged 18+ in 2016 is estimated to have been 592,000, representing about 3.2 per cent of the adult population. • the percentages identifying as non-heterosexual are higher at younger ages and lower at older ages, with the age gradient being more pronounced for females. • as would be expected, the most populous states, new south wales, victoria and queensland, are home to the largest non-heterosexual populations, while the act, tasmania and the northern territory have the smallest populations. • as a fraction of the total population, south australia, western australia and the northern territory have the smallest percentages identifying as non-heterosexual (2.6%), while the act has the highest (5.1%). ethics approval approval for this study was received from the charles darwin university human research ethics committee (approval h17122). contact: ethics@cdu.edu.au. acknowledgements we gratefully acknowledge helpful advice received from emeritus professor gary gates during the course of this study, and the helpful comments of the anonymous reviewers on an earlier version of this paper. our thanks and appreciation is also extended to hamish mcmanus from the kirby institute, unsw, who extracted data from the ashr2, and laura bennetts-kneebone from the commonwealth department of social services who extracted data from the 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journal website: www.australianpopulationstudies.org commentary a whole-of-government approach to population policy for australia liz allen* the australian national university * corresponding author. email: liz.allen@anu.edu.au. address: beryl rawson building (#13), centre for social research and methods, the australian national university, act 2606, australia. paper received 16 august 2018; accepted 3 november 2018; published 12 november 2018 1. introduction australia is in the midst of a popularly-constructed crisis of population. this so-called crisis, in social terms, is not dissimilar to the many which have come before in australia’s history. yet australia’s contemporary crisis differs in that the focus of the oft-referred-to population debate has come to revolve primarily around immigration and the politics of problematising population. the problematisation of population occurs in many countries across the world, and is much about immigration and the effects of migrants on settlement areas, particularly as fertility has declined. constructing population as a social problem means any consideration of population-related matters typically results in the portrayal of population, specifically immigration, as the root cause of social ills. talk of population has, unhelpfully, come to focus on race and ethnicity. for example, with ambivalence japan has widened immigration intake to allow additional visas for much-needed skilled workers (murakami 2018). despite the need for migrants, japanese people are concerned about the effects of foreign workers. concerns relate to whether migrant workers will fit in and what pressures they might place on the pension and welfare scheme. apparent concerns also relate to how immigration will change japan. in a more overt example of problematisation, the united states president donald trump has framed immigration as a threat to the american people (bennett 2017). population growth in australia, fuelled by net overseas migration, has prompted calls from politicians and social commentators across the political spectrum for a population inquiry and policy debate. questions have been raised over what might be the best, and or, sustainable population size for australia; and more importantly, whether greater intervention is needed to restrict the level of migration and the source countries of migrants. current calls for a population policy reflect wider social concerns which have come to be conflated with population growth (especially due to immigration), including housing affordability, adequacy of public infrastructure, and environmental conservation. a dominant narrative has emerged: inequality is further exacerbated by migration, conjuring nationalist and protectionist sentiments. http://www.australianpopulationstudies.org/ mailto:liz.allen@anu.edu.au australian population studies 2 (2) 2018 allen 23 the present social and political contexts are such that a population policy is likely for the first time in the country’s recent history. the government has indeed signalled a population policy (focused on migrant settlement) will be put forward with haste (benson 2018). yet exactly what constitutes an appropriate population policy for contemporary australia is still yet to be determined. the breadth of population-related issues lends itself to an approach which seeks to embed and contextualise population among wider government business – which requires a whole-of-government, joined-up approach. 2. background population policies, as a general principle, seek to address or influence components of population change, namely births, deaths and migration (demeny 1975). the concept of population policies conjures notions of restrictive and coercive government interventions designed to control various aspects of people’s lives. it is considered that australia already has a quasi or de facto population policy by way of the migration program (allen 2011; mcdonald 2003; productivity commission 2016). the migration program is currently capped at 190,000 permanent migrants per year. while this cap has gone unchanged since 2012, the actual intake has fluctuated below the cap in recent years (treasury 2018). despite the spectre of population as an ongoing feature in the australian political landscape, australia has not had an official population policy since the early-1970s (allen 2011; jones 1997). this most recent population policy was established following the second world war when a growth target of 2 per cent was set to bolster population growth, equally through births and immigration. australia’s last population policy was in response to fears australia was unable to defend itself against the threat of external foreign power (jones 1997). population inquiries are dotted throughout australia’s history (allen 2017). the most recent, the sustainable population strategy for australia, was completed in 2011 after concerns over a ‘big’ australia, and echoed the findings of previous inquiries (allen 2011). hundreds of submissions were received from a wide range of organisations and individuals. grand statements and commitments were made as part of the latest inquiry, relating to how the government of the day would address the population crisis. no population targets were set (dsewpc 2011). the year-long process and fanfare of the report release conjured a feeling of change (allen 2017). the sense of change was short-lived as it became clear the population strategy was in name only, as the existing policy environment continued. the enduring finding of australia’s population inquiries has been that preparedness and responsiveness are central for the nation to weather demographic difficulties (allen 2017). quality population data – especially from censuses, births, deaths and migration, and population projections – are vital to being prepared and responsive to the demographic needs of the future. intergenerational reports (igr) published by the federal treasury department, roughly every five years, are an important part of informing strategic direction using demographic and economic data about now and what might be into the future. the most recent igr, in 2015, was accompanied by the public awareness campaign challenge of change (treasury 2015). public backlash over the costs, lack of environmental considerations, and political tone of the campaign doomed the only real attempt australia has seen in recent time to engage the nation in a conversation about its demographic future. and what australia is presented with, in demographic terms is about managing change. 24 allen australian population studies 2 (2) 2018 popular and political discourse portrays a crisis of overpopulation in contemporary australia. focus on australia’s size and growth has undeniable political motivations, particularly in the present response from the minor and major political parties. leaders from the two major political parties have commented publicly on immigration and its impacts on australia. the leader of the opposition, bill shorten, has expressed concern that the number of overseas migrants is adversely impacting on wages and contributing to insecure and inaccessible paid work for locals. shorten has argued for a reduction in temporary migration (baxendale 2018). in contrast, the conservative prime minister, scott morrison, supports the current migration program. as treasurer, morrison promoted the economic benefits of current overseas migration levels (murphy 2018). the minister responsible for the broad home affairs portfolio, peter dutton, has called for lowering migrant intake as well as a preference for people from racially similar backgrounds as the majority australian population (koziol 2018). the minister directly responsible for immigration, david coleman, advocates the social and economic value of multiculturalism in australia (acharya 2018). conversely alan tudge, the minister responsible for population (among cities and urban infrastructure), has been colloquially appointed as the congestion-buster (elton-pym 2018). tudge has proposed australia makes more concerted efforts to encourage settlement of overseas migrants into regional areas, or in the least areas outside the three major cities of sydney, melbourne and brisbane. overpopulation in the three major cities has featured among tudge’s rhetoric. minor parties in australia have put forward a number of proposals during 2018 concerning immigration and race. an immigration plebiscite was proposed by the leader of the minor nationalist party, pauline hanson. hanson’s proposed immigration plebiscite reflects growing sentiment among those opposed to current migration intake that all australians should have a say about the level of immigration. hanson also sought recognition of the australian parliament that it is ‘ok to be white’ (karp 2018a). while the motion was inadvertently supported by the government, parliament voted narrowly against it. additionally, a failed attempt to hold a plebiscite to limit immigration from only european countries was proposed by fraser anning, a member of another minor australian nationalist party (mcculloch 2018). anning has since been expelled from his party due to his raciallymotivated public commentary (karp 2018b). data tell an interesting story, and contextualise the populist problematisation of population in australia. population growth in australia at 1.6% (for the year to 30 june 2017) is higher than the world average and considerably higher than countries among those in the organisation for economic co-operation and development (oecd), in particular canada, the united kingdom, and the united states (allen 2018a). figure 1 shows population growth in australia has been strong over the 10 years to 2017 (in the context of annual growth since 1945), despite the global financial crisis (gfc). it is not surprising that australia emerged from the gfc comparatively unscathed when compared with similar countries. strong population growth and economic measures taken by the then government were major factors. driving the majority of population growth over the past 12 years has been net overseas migration (abs 2018a). figure 2 presents the contributions of net overseas migration and natural increase to total population growth since 1975, which was when fertility dropped to replacement level before falling to below-replacement levels, where it has remained since (allen 2018a). australian population studies 2 (2) 2018 allen 25 figure 1: annual population growth, australia, 1945-2017 source: abs 2014; abs 2018a. notes: annual figures to 30 june. figure 2: components of population change, australia, 1975-2017 source: abs 2014; abs 2018a. notes: annual figures to 30 june. the definition used in calculating estimates of net overseas migration (nom) changed in 2006. caution should be taken when comparing nom over time. overseas migration has become a vital component of the population and economic landscape in australia as a response to population ageing. population ageing is increasing old-age related dependency, meaning growing pressure on the working age population to contribute income tax to fund government-provided essential services (allen 2017). recent immigration in australia has been shown to affect greater rates of labour force participation (treasury 2018; productivity commission 26 allen australian population studies 2 (2) 2018 2016), helping to moderate the adverse economic pressures of an ageing population by way of the co-called dependency burden (allen 2018b). figure 3 illustrates the increasing dependency rates over the 1975 to 2017 period. figure 3: age-related dependency ratios, australia, 1975-2017 source: abs 2014; abs 2018a. notes: annual figures to 30 june. government spending is highest for people aged over 65 years according to rice, temple and mcdonald (2014; cited in treasury 2015). increasing old-age dependency thus has clear consequences for the fiscal pressures on government spending and flow on impacts for people in the labour force contributing income tax. furthermore, a worrying risk emerges whereby young people – the future workforce – compete for government spending for more pressing and costly demographic demands. socioeconomic and demographic inequality thus becomes a risk facing australia. alongside this inequality is the unequal opportunities experienced throughout australian towns and communities. the three major cities along australia’s east coast welcome the largest share of immigration. population growth is greatest in the capital cities of melbourne (2.7% in the year to 30 june 2017), sydney (2.0%) and brisbane (2.0%). conversely, areas outside these capitals experience vastly different growth rates, and even decline (as is the case in areas outside the capital in the northern territory). furthermore, there are regions across australia with declining or struggling populations, largely due to changing labour force supply and demand. planning and infrastructure are playing catch-up in australia. rather than face head on the infrastructure and planning challenges posed by population growth, it has been suggested that the strategy in recent decades has been for the states with the majority share of immigration to ignore infrastructure needs (hartcher 2018). this has resulted in two-speed population growth story. cities australian population studies 2 (2) 2018 allen 27 are under pressure to accommodate population, whereas regional areas are under pressure to retain or attract population. unequal population distribution across australia highlights population pressure points and exacerbates the notion that population is problematic. there are have been a number of attempts in recent decades to encourage migrants to establish themselves initially in regional areas upon moving to australia, with the hope that immigrants might establish themselves and stay on in these areas. towns have initiated migrant settlements, including the highly publicised luv-a-duck business which offers a good case study into how small towns can attract population, with adequate employment opportunities. the nhill community in rural western victoria teamed up with the local duck farm and processing plant to settle karen refugees from myanmar in the area to fill much needed skills at luva-duck (ames & deloitte access economics 2015). the nhill example highlights the need for viable opportunities for migrants to maximise success. destination areas must offer essential services and infrastructure for migrants to be able to establish themselves socially, culturally and economically. similarly, such opportunities could also attract local internal migration. 3. a population policy for the future the demographic pressures of population ageing in australia demand a contemporary rethink of the approach to the development of population policy. the issue of population cannot be merely reduced to numbers or demographic statistics about births, deaths and migration. nor is population just about age composition, population distribution, and labour force participation. migration remains an ongoing feature of a population policy for australia, as does infrastructure which supports the population (physical, social, environmental or economic). australia must look to make opportunities of its demographic challenges by being prepared and responsive to population composition which might adversely impact national socioeconomic wellbeing. considerations of a population policy for australia include: health, education, gender equality, family-friendly workplaces, transportation, housing, land use, green space, water supply, food production, energy use, environmental sustainability, settlement distribution, and climate change, and many more. population policy reflects myriad complex social issues which sit across numerous ministerial portfolios, necessitating a whole-of-government approach to population policy. the reasons most recent attempts at population policy in australia have been unsuccessful might lie in the fact that a coordinated approach is necessary and has not been attempted or achieved. a reconnection of the disparately placed pieces of the population puzzle might be the best way forward for a contemporary population policy for australia. carey, mcloughlin & crammond (2015 p. 176) point to how ‘joinedup government’ is required to address complex or ‘wicked’ social problems, ‘and overcome siloed departmental approaches’. carey and colleagues demonstrate how socially complex issues which cross departmental boundaries and have interdependencies between issues can be successfully addressed through whole-ofgovernment, joined-up approaches. drawing on the australian government’s approach to the complex problem of social inclusion, carey et al. (2015) show how multidimensional, complex and contested social issues can effectively move beyond impasse via what the authors refer to as innovation narratives. 28 allen australian population studies 2 (2) 2018 innovation narratives enable a change to how a complex issue is perceived, and so shift values to facilitate the desired change (carey, mcloughlin & crammond 2015). carey and colleagues warn that innovation narratives are not about behaviour modification, but rather they can challenge thinking with the aim to change perceptions. innovation narratives are effective at gaining coherence within policyand decision-makers across government departments, but they can also be extended to community involvement. storytelling and communication are crucial to innovation narratives through the coordination of people and ideas and dissemination of information. while innovation narratives are shown to be effective among policy makers (carey 2016; carey, mcloughlin & crammond 2015), such an approach to elicit perception change could be trialled to bring the population policy domain together. it is unlikely, nor ideal, that all australians will agree on population matters. what is possible (and more helpful) is the mobilisation of the australian public with the common goal in mind that at the heart of population matters is the one aim to achieve a fair australia in which wellbeing is the paramount concern. through this process, population ceases to be the issue. what becomes the focus, instead, is the infrastructure and support for australians. more importantly, government core business is to deliver for the people, not blame people (locals or migrants). despite the failed attempt to promote the evolving needs associated with a changing demography under the guise of the challenge of change campaign, the aim of such a campaign is a positive move forward (allen 2017). a worthwhile endeavour would be to reconsider the option of innovation narratives through a change management communication strategy. this requires politicians to refrain from framing population (particularly immigration) as problematic. ideally, such an undertaking would be non-partisan. however, a non-partisan approach to population-related matters is unlikely. nonetheless, an attempt to do so would be worthwhile. because population features in many areas of government, an effective coordinated approach to policy is difficult. establishing a minister, ministerial body, or agency with oversight to ensure adequate progress within a population framework is one solution to overcome, or in the very least, minimise the difficulties of the breadth of population-related matters in policy. such a framework would not be easy, though would position australia well for the demographic challenges of the future. carey et al. (2015 p. 184) suggest the development of ‘supportive architecture’ to maximise the potential success of a whole-of-government approach. lines of accountability should be among the first things to establish. new administrative structures – and thus new ways of doing population policy – to support clear accountability can help achieve integration and a breaking down of departmental silos (carey, mcloughlin & crammond 2015). possible points of failure in a whole-ofgovernment approach to population policy include: inadequate government and/or departmental commitment, opposing ideologies among ministers, and rigid organisational structures. according to carey and colleagues (2015 p. 183) apart from a mandate for change embedded in policy, ‘establishing coherence between institutional and operational level action’ is essential to implementing a whole-of-government approach to population policy for australia. to this end, flexibility, coherence and communication are vital. this new way of approaching population policy requires evidence and a framework for assessing achievements. the development of a framework with a set of measureable indicators to report and monitor success towards population-related wellbeing could provide an opportunity for the public to remain australian population studies 2 (2) 2018 allen 29 informed of australia’s progress. such a framework, and related indictors, could be modelled after the global sustainable development goals (undp 2018) and be reported on as part of the igr process. release of five-yearly igrs could coincide with the release of australian bureau of statistics population projections. publication of data and information informing the igr and evaluation framework via a publically accessible website would help facilitate evidence-sharing for communities across australia. an overall population target, or even a target for growth is unnecessary, and has the potential to lead to coercive or restrictive measures. the current approach for setting the annual permanent migration cap is sensible, and allows for flexibility to enable a temporary migrant intake which is demand-driven. a focus on size and growth rates has been a major factor in the current population discourse and has had the effect of shifting the attention away from productive action onto matters of race and ethnicity. this numbers game is harmful. optimal or carrying capacity population size is not determinable for australia as technological advancements prohibit any sensible calculation. it may be that innovation is the major limitation for growth. additionally, there is a paucity of good quality up-to-date research identifying the best migrant intake for australia to maximise social and economic benefits. an effective migration scheme should be informed by evidence. a program of research to inform such an evidence base for australia’s migration program would guarantee the necessary investments were made in a timely and responsive manner and the intake did not lead to adverse consequences. 4. conclusion population policy is necessary in australia, not only because of the current political and populist climate, but because of the demographic challenges which lie ahead. an official population policy would address both the present problematising of demographic difficulties. the so-called population crisis is not so much a crisis of numbers or people but rather a crisis of long-term inaction. a population policy for australia should provide a blueprint for the future – a framework for what the nation aspires to be. the process to create a population policy for australia need not be by way of a formal inquiry. more importantly, consensus or majority public opinion is not necessary for the type of population policy proposed here. a public process of sorts, nonetheless, is advised. current population discourse would be well served through innovation narratives seeking to shift the perceived problem of population. such innovation narratives could be facilitated by an administrative population body within government. whole-of-government oversight to ensure communication and action is effective across ministerial portfolios is a necessary component of a population policy. evidence gathering from and by experts, alongside a process of community communication through innovation narratives, would provide a solid foundation for which government could establish a framework for the future of australia. the most effective population policy for australia is one which embeds population-related concerns and issues in the foundation of funding and policy-making processes. in doing so, population is no 30 allen australian population studies 2 (2) 2018 longer stigmatised. instead, population is placed as the basis for government plans for the future, and evidence will help guide the path forward. 5. key messages • a whole-of-government approach, reflecting population-related interdependencies across government departments, is 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repository.anu.edu.au/bitstream/1885/12260/4/nta_report_2014_r.pdf. accessed on 9 august 2018. treasury (2015) 2015 intergenerational report: australia in 2055. canberra: the treasury. treasury (2018) shaping a nation: population growth and immigration over time. canberra: the treasury. undp (2018) sustainable development goals. http://www.undp.org/content/undp/en/home/sustainable-development-goals.html. accessed on 6 november 2018. https://openresearch-repository.anu.edu.au/bitstream/1885/12260/4/nta_report_2014_r.pdf http://www.undp.org/content/undp/en/home/sustainable-development-goals.html 5. key messages references australian population studies 2017 | volume 1 | issue 1 | pages 41–54 © bernard, forder, kendig and byles 2017. © published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org residential mobility in australia and the united states: a retrospective study aude bernard* the university of queensland peta forder the university of newcastle hal kendig australian national university julie byles the university of newcastle *corresponding author. email: a.bernard@uq.edu.au. address: chamberlain building, queensland centre for population research, school of earth and environmental sciences, the university of queensland, st lucia qld 4072 paper received 11 august 2017; accepted 27 october 2017; published 20 november 2017 abstract background levels of internal migration vary significantly between countries. australia and the united states consistently record among the highest levels of migration anywhere in the world. very little is known, however, about the factors underlying mobility differentials. we argue that this is because existing evidence is almost exclusively based on period measures applied to cross-sectional data. aims we seek to advance understanding of cross-national variations in levels of residential mobility by drawing on a newly proposed suite of cohort migration measures, coupled with the recent release of internationally comparable retrospective residential history data. data and methods focusing on the early cohort of baby boomers born between 1947 and 1951, the paper examines residential mobility levels and patterns in early and mid-adulthood in australia and the united states and compares them with 14 european countries. differences in completed levels of residential mobility are assessed in terms of four components: the proportion of a cohort who moved at least once; mean age at first move; mean age at last move; and average interval between moves. results while cohort analysis confirms high levels of mobility in australia and the united states, it does not support the notion of a common ‘new world’ mobility regime distinct from other advanced economies. conclusion a cohort perspective offers refined insights into population mobility. the increasing availability of retrospective survey data means that researchers can now apply cohort measures to a wide range of countries. key words retrospective life histories; residential mobility; cohort migration; completed migration rate; completed migration distribution; migration progression ratio; australia; united states. http://www.australianpopulationstudies.org/ mailto:a.bernard@uq.edu.au 42 bernard a et al. australian population studies 1 (1) 2017 1. introduction ‘new world’ countries such as australia, canada, new zealand and the united states are firmly established as some of the most mobile countries in the world with 40 to 55 per cent of their populations changing residence over a five-year period (bell et al. 2017). in a seminal cross-national comparison, long (1991) attributed this high mobility to institutional frameworks, flexible housing and labour markets and peripatetic traditions inherited from immigrant forbears. more recently, in a comparison of 23 organisation for economic co-operation and development (oecd) countries, sánchez and andrews (2011) showed that australia ranked second after iceland, and the united states fourth after sweden in terms of the proportion of households changing residence over a twoyear period. similar variations in levels of internal migration were found in a global comparison of 139 countries (esipova, pugliese and ray 2013). these movements have occurred against a background of globalisation, urbanisation and population ageing (mcdonald 2017). in most countries, internal migration has become a leading agent of demographic change, shaping patterns of human settlement and affecting the age distribution of populations. this paper adopts a cohort perspective to advance understanding of levels and patterns of residential mobility in australia and the united states. a cohort approach provides distinct advantages over existing studies, which use period measures applied to cross-sectional data. first, by following individuals over their entire life course, a cohort perspective provides detailed information about the migration trajectories of different birth cohorts (bogue 1950; shyrock and larmon 1965). this can reveal how moves are distributed in the population, which cannot be achieved with the dichotomy between movers and non-movers commonly used in national censuses and surveys (xu-doeve 2006). thus, because it views migration as an incremental process where individuals progress from one move to the next, a cohort approach allows the association between the timing of migration and the number of lifetime moves to be explored, which can shed light on the demographic mechanisms underlying differences in migration levels (bernard 2017b). second, a cohort perspective has the advantage of eliminating any potential tempo effects, which inflate or deflate the period measure of a demographic event due to a rise or fall in the mean age at which the event occurs (bongaarts and feeney 2008). cohort migration is free of this interpretive difficulty. if cohort migration falls, it is a pure quantum effect: people are moving less. third, because individuals may live through periods of high and low migration, a cohort approach has the advantage of smoothing out temporal variations in migration levels. this is particularly important when comparing countries because the economic cycles, housing market conditions and government policy regimes that underpin short-term variations in migration level are unlikely to be in phase in different national contexts (bell et al. 2002). finally, comparing the migration trajectories of successive cohorts can reveal the influence of social change on the evolution of migration behaviour, while comparisons between countries can shed light on the effects of national economic, social and policy developments (kendig and nazroo 2016). to facilitate a structured approach to the cohort analysis of migration and residential mobility, bernard (2017a) has recently proposed a comprehensive suite of robust cohort measures that capture the level and distribution of completed migration and the timing and spacing of moves. application to european countries (bernard 2017b) has revealed that differences in cohort migration levels are attributable to variations in the extent of repeat movement, which is underpinned by differences in mean ages at first and last move. australian population studies 1 (1) 2017 bernard a et al. 43 we now examine the demographic mechanisms underpinning variations in residential mobility levels in two ‘new world’ countries. we draw retrospective residential history data from the life histories and health (lhh) survey in australia and the life history mail survey (lhms) in the united states. while the lhms surveyed a nationally representative sample of americans born before 1966, the lhh survey focused on early baby boomers born between 1947 and 1951 and living in new south wales at the time of the survey. the latter may therefore not be representative of all australians. the surveys collected retrospective lifetime residential mobility histories in 2011–2012 and 2015– 2016, respectively, using life-history grids. this approach involves showing respondents a schematic form that depicts the year in their life, from birth to present, alongside national and world events to help them recall past moves (belli 1998; blane 1996). while the life-history calendar only took the form of a mail survey in the united states, it was complemented in australia by computer-assisted telephone interviews to assist recall (kendig et al. 2014). despite these differences, response rates were similar in the two countries, sitting at 45 per cent in australia and 48 per cent in the united states. to position australia and the united states internationally, we complement these datasets with retrospective residential histories from the english longitudinal study of ageing (elsa) and the survey of health, ageing and retirement in europe (share). together these provide directly comparable residential histories for 14 european countries (börsch-supan 2010; marmot et al. 2016). the paper explores variations in levels and patterns of residential mobility for the cohort of baby-boomers born in each case study country between 1947 and 1951 by comparing completed migration rates, completed migration distribution and the cumulative distribution of movers by age and move order. 2. cohort measures of migration: methods and data the analysis presented here is confined to a subset of six measures recommended by bernard (2017a) to compare migration between cohorts and countries. while we apply these measures to residential mobility (i.e. changes of address), we use the term ‘cohort migration’ proposed by bernard (2017a). table 1 lists each measure in summary form, providing a definition and an algebraic representation, where m corresponds to the number of moves, p to the number of individuals and x to the age at move. subscript i refers to the order of each move (first, second, etc.) and n to an individual. thus, 𝑃𝑖 refers to the number of individuals who have moved i times, 𝑀𝑖 to the number of moves of order i for all i>0, and 𝑋𝑛 corresponds to the age at move of individual n. multiple measures are required to comprehensively quantify cohort migration: • the first of these measures is the completed migration rate (cmr), which represents the average number of moves undertaken by members of a given cohort over the course of their lives, as defined by equation (1) in table 1. it is readily comparable across countries and indicates whether the overall level of migration is high or low. • because the actual migration behaviour of individuals is more heterogeneous than this summary statistic suggests, the completed migration distribution (cmd) decomposes the population according to the number of moves individuals have made, as indicated in equation (2), and hence reveals the proportion of lifetime non-movers, infrequent movers and frequent movers. • migration progression ratios (mprs) depict the underlying, incremental process of moving by measuring the proportion of individuals who, having made a given number of moves, proceed to move at least one more time, as shown in equation (3). underpinning mprs is the idea that variation in migration behaviour depends on the number of times individuals have moved. 44 bernard a et al. australian population studies 1 (1) 2017 • mean migration age (mma) summarises migration age patterns by showing whether populations are moving early or late in life. it can be computed for all moves, as indicated by equation (4), or by move order, as shown by equation (5). of particular importance are (a) the mean age at first move, because it captures the start of the migration career of successive cohorts and (b) the mean age at last move, which indicates how early or late in life different populations stop moving. • the final measure, mean migration spacing (mms), relates to spacing between consecutive moves, which indicates the extent to which moves are close to each other or spaced further apart, as shown by equation (6). further information and worked examples can be found in bernard (2017a). table 1: cohort measures of migration source: bernard (2017a). notes: m is the number of moves; p is the number of individuals; x is the age at move; i refers to the order of the move; n refers to an individual. to maximise comparability between lhh and lhms and avoid censoring bias, the analysis is confined to individuals born between 1947 and 1951 in each case study country. to ensure that migration careers are of comparable lengths for different birth years, the paper focuses on moves undertaken during early and middle adulthood, between the ages of 17 and 50 years (inclusive), and excludes tied moves in childhood that are qualitatively different to moves made as independent adults. in both surveys, respondents were asked to report the start and end years of residence for dwellings in which they had lived for more than six months since birth (up to 29 dwellings in lhh and up to 18 dwellings in the lhms). the postcode was collected in both surveys but, to ensure confidentiality, an annual indicator of change of residence and change of state was constructed for the lhms, whereas geographic information was released at city level for the lhh. to ensure comparability, the analysis in this paper makes use of data for up to 18 moves and uses all changes of postcodes, independent of administrative units, in measuring migration. while this means that the distinction between short and long-distance moves cannot be made, the results have the advantage of not being affected by differences across countries and over time in the number and shape of spatial units, which can bias cross-national comparisons (courgeau 1973). measures definition method equation completed migration rate (cmr) average number of moves per individual by the end of their migratory life 𝐶𝑀𝑅 = 𝑀 𝑃⁄ (1) completed migration distribution (cmd) proportion of cohort who have moved exactly i times 𝐶𝑀𝐷(0,𝑖) = 𝑃𝑖 𝑃 (2) migration progression ratios (mprs) proportion of individuals who moved i times and who went on to move at least once more 𝑀𝑃𝑅(𝑖,𝑖+1) = 𝑀𝑖+1 𝑀𝑖 (3) migration mean age (mma) mean age at which individuals in cohort moved 𝑀𝑀𝐴 = ∑ ∑ 𝑋𝑛,𝑖 𝐼 𝑖=1 𝑁 𝑛=1 𝑀⁄ (4) order-specific migration mean age (mma) mean age at which individuals in cohort moved for the ith time 𝑀𝑀𝐴𝑖 = ∑ 𝑋𝑛.𝑖 𝑁 𝑛=1 𝑀𝑖⁄ (5) mean migration spacing (mms) average interval between all moves for individuals who have moved at least twice 𝑀𝑀𝑆 = ∑ (𝑀𝑀𝐴𝑖+1 − 𝑀𝑀𝐴𝑖 𝐼 𝑖=1 ) ∑ 𝑀𝑖 𝐼 𝑖=2 ⁄ (6) australian population studies 1 (1) 2017 bernard a et al. 45 3. cohort residential mobility in australia and the united states figure 1 ranks australia and the united states alongside 14 european countries from the highest to lowest completed migration rate (cmr). while both countries display a cmr well above the european mean of 2.9 moves, australia reports the highest level of residential mobility among the 16 countries, with an average of 5.1 moves per individual. the united states ranks fifth after australia, denmark, england and sweden, with one less move on average than australia. figure 1: completed migration rates: australia, united states and select european countries source: authors’ calculations from elsa, share, lhh and lhms data. note: changes of address between ages 17 to 50 years. to describe the actual range of mobility behaviours in each country, figure 2 (next page) reports the completed migration distribution (cmd), which decomposes populations according to the exact number of times people moved in their lives. the proportion of non-movers, infrequent movers and frequent movers in australia and the united states is compared to the european mean. the united states stands out for its significant proportion of non-movers. fully 15 per cent of american respondents reported having never changed residence in adulthood, which is more than twice the average proportion in europe and the second highest level after austria (bernard 2017b). in contrast, immobility in australia is very rare, with less than 2 per cent of respondents reporting no change of postcode, which is the third lowest level after denmark and sweden. both australia and the united states, however, display a high level of repeat movement. approximately five in 10 australians and four in 10 americans moved at least five times between the ages of 17 and 50, compared to an average of three in 10 people in europe. very frequent movers are especially characteristic of the australian mobility landscape, with 20 per cent of respondents reporting eight moves or more, compared with 13 per cent in the united states and a mean of 9 per cent in europe. 5.1 4.9 4.6 4.5 4.1 3.7 3.7 3.4 2.8 2.7 2.1 2.0 1.9 1.7 1.6 1.6 0 1 2 3 4 5 6 a u st ra lia d en m ar k en gl an d sw ed en u n it ed s ta te s n e th e rl an d s fr an ce sw it ze rl an d b el gi u m g e rm an y it al y sp ai n p o la n d c ze ch r ep u b lic a u st ri a g re ec e c o m p le te d m ig ra ti o n r at e 46 bernard a et al. australian population studies 1 (1) 2017 figure 2: completed migration distribution: australia, united states and european mean source: authors’ calculations from elsa, share, lhh and lhms data. notes: changes of address between ages 17 to 50 years; european mean obtained from the 14 countries in elsa and share. bernard (2017b) showed that variations in the extent of repeat movement are underpinned by differences in mean ages at first and last moves that together delineate the average length of migration careers. age at first move signals the start of an individual’s migratory life and is of particular importance because it influences the probability of subsequent moves. in countries where young adults first move early (i.e. early twenties), they subsequently move at younger ages than in countries where first-time movers are older (i.e. mid-twenties). in addition, younger adult movers are more likely to proceed to a subsequent move and consequently report higher numbers of moves throughout adulthood than late starters. we test this proportion for australia and the united states by plotting age at first move against the cmr. figure 3: age at first move by completed migration rate: australia and united states source: authors’ calculations from lhh and lhms data. note: changes of address between ages 17 to 50 years. 7 15 2 36 18 18 28 24 26 20 30 34 9 13 20 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% european mean united states australia 0 moves 1 to 2 moves 3 to 4 moves 5 to 7 moves 8 moves + r² = 0.7837 r² = 0.9271 0 1 2 3 4 5 6 7 17 18 19 20 21 22 23 24 25 26 27 28 29 30 c o m p le te d m ig ra ti o n r at e age at first move (years) united states australia australian population studies 1 (1) 2017 bernard a et al. 47 figure 3 reveals for both countries a clear negative association, confirming that later ages at first move in adulthood are associated with reduced lifetime mobility. the strength of this association is supported by a pearson’s correlation coefficient of -0.89 for the united states and -0.96 for australia. individuals who first moved at age 17 changed place or residence on average 5.9 times in the united states and 6.5 times in australia, compared with four times or less for individuals who first moved at age 25 or later in both countries. we further explore age differentials by reporting the cumulative distribution of movers by age and move order. we first analyse results for australia separately in figure 4, before comparing australia with the united states in figure 5. the results for australia show that the first and second moves are strongly concentrated in early adulthood, which conforms to the well-established age patterns of migration peaking in the mid-to-late twenties (bernard, bell and charles-edwards 2014a, 2014b; rogers and castro 1981). half the cohort have moved at least once by age 20 and more than 80 per cent by age 23. a year later, the same proportions have moved at least a second time. for both moves, the proportion of movers starts plateauing after age 30, which indicates that individuals who have not moved by that age never went on to move. the third and fourth moves occur a bit later in life and are spread across a broader age range. it is not until age 30 that 80 per cent of individuals who have moved twice proceed to a third move and it is not until age 36 than 80 per cent of individuals who have already moved three times undertook their fourth move. the curve for the third move plateaus around age 35, while the curve for the fourth move continues to increase at a slow rate, indicating a broader dispersion of the fourth move across the age spectrum. figure 4: cumulative distribution of movers by age and move order in australia source: authors’ calculations from lhh and lhms data. note: migration between ages 17 to 50 years. the cumulative proportion of movers at age 50 corresponds to the migration progression ratio (mpr). that is, the proportion of the cohort who having moved i times went on to move at least i +1 more times. while mprs decrease with move order, they remain high for all moves: as many as 89 per cent of individuals who moved three times moved at least one more time. this pattern underpins the high level of repeat movement identified in australia in figures 1 and 2. 0 25 50 75 100 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 c u m u la ti ve d is tr ib u ti o n o f m o ve rs ( % ) age at move (years) first move second move 48 bernard a et al. australian population studies 1 (1) 2017 we now compare age patterns between australia and the united states. figure 5 reveals that the key difference is in the progression to the first move. while the two countries first follow a similar progression in early adulthood, in the united states the proportion of first-time movers starts to plateau at around 80 per cent from age 25 onward. thus, americans who have not moved by age 25 never proceed to a move. conversely, in australia the proportion of first-time movers continues, increasing to 98 per cent by age 40. on the other hand, second-, thirdand fourth-time movers display very similar age patterns in the two countries and comparable proportions of movers by age 40. these results confirm that it is the proportion of non-movers that is the key factor underpinning differences in completed migration rates in australia and the united states. australia united states figure 5: cumulative distribution of movers by age and move order: australia and united states source: authors’ calculations from lhh and lhms data. note: migration between ages 17 to 40 years. we now seek to quantify the relative contribution of immobility to differences in completed migration rates. following jain and mcdonald’s (1997) approach to fertility analysis, bernard (2017a) demonstrated that the cmr can be expressed mathematically as a function of four components, 𝐶𝑀𝑅 = 𝑀𝑜[1 + ( 𝐿−𝐹 𝐼 )] (7) 0 25 50 75 100 17 19 21 23 25 27 29 31 33 35 37 39 c u m u la ti ve d is tr ib u ti o n o f m o ve rs ( % ) age at move (years) first move 0 25 50 75 100 17 19 21 23 25 27 29 31 33 35 37 39 c u m u la ti ve d is tr ib u ti o n o f m o ve rs ( % ) age at move (years) second move 0 25 50 75 100 17 19 21 23 25 27 29 31 33 35 37 39 c u m u la ti ve d is tr ib u ti o n o f m o ve rs ( % ) age at move (years) third move 0 25 50 75 100 17 19 21 23 25 27 29 31 33 35 37 39 c u m u la ti ve d is tr ib u ti o n o f m o ve rs ( % ) age at move (years) fourth move australian population studies 1 (1) 2017 bernard a et al. 49 where 𝑀𝑜 is the proportion of individuals who moved at least once, 𝐹 is the mean age at first move, 𝐿 is the mean age at last move and 𝐼 is the mean length of all intervals between consecutive moves for individuals who moved at least twice. table 2: components of completed migration rate: australia and united states proportion of movers (mo) mean age at first move (f) mean age at last move (l) mean length of migration interval (i) completed migration rate (cmr) australia 99.0 20.9 37.2 4.0 5.1 united states 84.7 20.6 36.7 4.5 4.1 % difference in cmr attributed to each component in united states compared to australia -16.9 1.4 -2.7 -3.8 -22.4 source: authors’ calculations from lhh and lhms data. note: migration between ages 17 to 50 years. table 2 reports each component of equation (7) for australia and the united states and shows the estimated percentage differences in cmr in the united states compared to australia. it reveals that the lower proportion of movers in the united states is overwhelmingly the main factor underpinning migration differentials between the two countries. of the 22.4 per cent different in cmr with australia, the proportion of movers accounts for 16.9 per cent. the impact of longer mean migration intervals on the cmr is much smaller, less than 4 per cent, as is the impact of the mean age at last move. the slightly younger mean age at first move has a small counteracting effect on cmr in the united states. measured as the difference between the mean ages at first and last move, the average length of migration careers is about 16 years in both australia and the united states. this is relatively long compared to that in other countries. in southern and eastern europe, for example, individuals are mobile on average for about seven years (bernard 2017b). figure 6: proportion of adult non-movers by birth cohort in the united states source: authors’ calculations from lhms data. note: migration between ages 17 to 50 years. 0 5 10 15 20 25 30 19 27 -1 9 31 19 32 -1 9 36 19 37 -1 9 41 19 42 -1 9 46 19 47 -1 9 51 19 52 -1 9 56 19 57 -1 9 61 p e rc e n ta ge w n o n ev er m o ve d ( % ) 50 bernard a et al. australian population studies 1 (1) 2017 is the relatively high level of adult immobility a long-standing feature of the american landscape or a characteristic of the cohort born between 1947 and 1951? to answer that this question, figure 6 (previous page) examines trends in immobility between ages 17 to 50 for seven successive cohorts born between 1927–1931 and 1957–1961. it shows that immobility among the early cohort of baby boomers (born 1947–1951) forms part of a declining trend of high immobility. the proportion of adult non-movers was at its highest level for individuals born 1927–1931 (26%). it then fell for successive cohorts, reaching a low of 13 per cent for the cohort born 1952–1956, before increasing again for the 1957–1961 cohort. 4. conclusion despite wide and enduring variations in migration levels between countries around the world, explanation for the relatively high mobility observed in ‘new world’ countries remains tentative. this can be traced in part to the limitations inherent in application of cross-national data to period measures, which fail to account for heterogeneity in migration behaviour or for cohort differentials. this paper has drawn on a series of robust cohort measures of migration, coupled with internationally comparable retrospective migration histories, to compare residential mobility levels and patterns in australia and the united states and identify key differences compared with 14 european countries for early baby-boomers born between 1947 and 1951. the results have confirmed a high level of residential mobility in australia and the united states, with the former reporting the highest level of residential mobility among the 16 oecd countries in our sample and the latter ranking fifth after denmark, england and sweden. high levels of mobility in both countries are attributable to the high incidence of repeat moves. approximately five in 10 australians and four in 10 americans moved at least five times in adulthood, compared with an average of three in 10 people in the 14 european countries. very frequent moves were especially characteristic of australia, where 20 per cent of respondents reported eight moves or more. compared with australia, the united states combines a high level of repeat moves with a substantial rate of immobility. while less than 2 per cent of australians never moved in adulthood, as many as 15 per cent of americans remained immobile. this is more than twice the average proportion of nonmovers in europe and is the second highest level among the 16 oecd countries. immobility appears to be an enduring characteristic of the united states that has persisted across successive cohorts born between 1927 and 1961. although its incidence has progressively diminished, it remains close to 15 per cent for the most recent cohort. cohort analysis does not support the notion of a common ‘new world’ mobility regime distinct from other advanced economies. while australia’s very high level of mobility may be inflated as a result of the lhh sample being drawn exclusively from the state of new south wales, its mobility level and patterns correspond to the mobility regime of northern and western european countries. in these countries, high mobility is the product of the extremely low incidence of immobility and a high level of repeat movement. this, in turn, is underpinned by an early mean age at first move and a late mean age at last move, which together support long migration careers (bernard 2017b). because of its high level of immobility, the united states departs from this mobility regime and does not conform to the patterns identified in oecd countries with intermediate levels of residential mobility, such as the netherlands, france, switzerland and belgium, where immobility is very low and the level of repeat australian population studies 1 (1) 2017 bernard a et al. 51 movement moderate. this suggests that the united states has a distinct mobility regime characterised by a unique combination of a high level of repeat movement and a high rate of immobility. as with any retrospective data, residential histories face issues of recall and are based on survivors only. although survivor bias is expected to be small, the completed migration rate should, strictly speaking, be interpreted as the average number of moves undertaken by members of a cohort conditional on survival to the date of the survey. bearing these limitations in mind, a cohort perspective offers a step forward in the comparative analysis of residential mobility by revealing new insights into mobility behaviour. it provides a robust foundation for exploring the demographic mechanisms underpinning migration differentials that parallel methods long used in fertility and mortality analysis. this paper has shown that moving beyond population-level averages and considering the distribution of moves provides a realistic description of the mobility experience of each cohort and offers refined insights into mobility behaviour. of particular importance is the negative association between age at first move and completed migration, which indicates that late starters in australia and the united states move less throughout the course of their adult lives. bernard (2017a, 2017b) showed that age at first move operates to affect completed migration by influencing the likelihood of progressing to moves of higher orders and that, in turn, variations in mean age at first move underpin differences in completed migration over time and between countries. the association between age at first move and completed migration may also result from a selection effect whereby individuals who view mobility more positively choose to start moving at younger adult ages, or that the experience gained from a previous move may facilitate subsequent migrations (van arsdol, sabagh and butler 1968). in this paper, we have shown that age also matters because individuals who have not moved by the age 25 in the united states and age 30 in australia remained immobile through their adult lives. thus, moves in early adulthood seem to have a lifelong imprint on mobility behaviour. differences in population composition are likely to account for some of the variation in residential mobility observed in this paper. the cohort measures employed here can be readily applied to specific groups to explore within and between country differences, differences between socioeconomic and ethnic groups and differences between nativeand foreign-born populations. better understanding of the role of population heterogeneity would represent an important step forward in the comparative analysis and understanding of migration and residential mobility. the distinctively high proportion of non-movers in the united states also invites investigation into reasons for immobility in that country and in other national settings to identify the underpinning factors. attention to the determinants of repeat movement, which accounts for most of the differences in completed migration between the 16 oecd countries, is needed also to establish the individual-level characteristics associated with repeat movement at a range of spatial scales and in different countries. key messages • cohort migration measures facilitate a structured and systematic analysis of retrospective residential history data • application of these measures to residential histories collected in australia and the united states has shown a high level of repeat movement in both countries, and a much a higher proportion of immobility in the united states. 52 bernard a et al. australian population studies 1 (1) 2017 • individuals who had not moved by age 25 in the united states and age 30 in australia remained immobile through their adult lives. this suggests that moves in early adulthood have a lifelong imprint on mobility behaviour. acknowledgments the authors gratefully acknowledge the support of the australian research council (arc) through the arc centre of excellence in population ageing research (ce110001029), arc discovery project (dp1096778) and arc discovery early career researcher award (de160101574). the authors thank emeritus professor martin bell for providing comments on a draft version of the paper. the life history and health (lhh) survey was approved by the university of sydney human research ethics committee (#12744) and supported by an australian research council grant (dp1096778, ‘socio-economic determinants and health inequalities over the life-course: australian and english comparisons’). chief investigators were prof. hal kendig (anu), prof. julie byles (the university of newcastle) and prof. james nazroo (the university of manchester). fieldwork and the sample are described in kendig et al. (2014). this research was supported by the australian research council centre of excellence in population ageing research and by infrastructure and staff of the priority research centre for gender, health and ageing. the lhh research was completed as a sub-study of the 45 and up study. the 45 and up study is managed by the sax institute (www.saxinstitute.org.au) in collaboration with partners: cancer council nsw; national heart foundation of australia (nsw); nsw ministry of health; nsw department of family and community services; disability council nsw; and australian red cross blood service. we thank the many thousands of people participating in the 45 and up study. the 2015 life history mail survey (lhms) contains questions about residential history, education history and other important childhood and family events. the lhms is part of the university of michigan health and retirement study, supported by the national institute on aging and social security administration in the united states. the share data collection has been primarily funded by the european commission through fp5 (qlk6-ct-2001-00360), fp6 (share-i3: rii-ct-2006-062193, compare: cit5-ct-2005-028857, sharelife: cit4-ct-2006-028812) and fp7 (share-prep: n°211909, share-leap: n°227822, share m4: n°261982). additional funding from the german ministry of education and research, the max planck society for the advancement of science, the u.s. national institute on aging (u01_ag0974013s2, p01_ag005842, p01_ag08291, p30_ag12815, r21_ag025169, y1-ag-4553-01, iag_bsr06-11, ogha_04-064, hhsn271201300071c) and from various national funding sources is gratefully acknowledged (see www.share-project.org). the elsa datasets were made available through the uk data archive. elsa was developed by a team of researchers based at natcen social research, university college london and the institute for fiscal studies. the data were collected by natcen social research. the funding is provided by the national institute of aging in the united states and a consortium of uk government departments coordinated by the office for national statistics. the developers and funders of elsa and the archive do not bear any responsibility for the analyses or interpretations presented here. http://www.saxinstitute.org.au/ http://www.share-project.org/ australian population studies 1 (1) 2017 bernard a et al. 53 references bell m, blake m, boyle p, duke-williams o, rees p, stillwell j and hugo g (2002) cross-national comparison of internal migration: issues and measures. journal of the royal statistical society: series a (statistics in society) 165(3): 435–464. bell m, charles-edward e, bernard a and ueffing p (2017) global trends in internal migration. in: champion t, cooke t j and shuttleworth i (eds) internal migration in the developed world: are we becoming less mobile? london uk: routledge; 76–97. belli r f (1998) the structure of autobiographical memory and the event history calendar: potential improvements in the quality of retrospective reports in surveys. memory 6(4): 383–406. bernard a (2017a) cohort measures of internal migration: understanding long-term trends. demography. [online ahead of print] doi: 10.1007/s13524-017-0626-7. bernard a (2017b) levels and patterns of internal migration in europe: a cohort perspective. population studies 71(3): 293–311. doi: 10.1080/00324728.2017.1360932. bernard a, bell m and charles-edwards e (2014a) improved measures for the cross-national comparison of age profiles of internal migration. population studies 68(2): 179–195. bernard a, bell m and charles-edwards e (2014b) life-course transitions and the age profile of internal migration. population and development review 40(2): 231–239. blane d b (1996) collecting retrospective data: development of a reliable method and a pilot study of its use. social science & medicine 42(5): 751–757. bogue d j (1950) an exploratory study of migration and labor mobility using social security data. scripps foundation for research in population problems, miami university. bongaarts j and feeney g (2008) the quantum and tempo of life-cycle events. in: barbi e, vaupel j w and bongaarts j (eds) how long do we live? demographic models and reflections on tempo effects. berlin: springer; 29–65. börsch-supan a (2010) survey of health, ageing and retirement in europe (share) wave 3 – sharelife. release version: 5.0.0. share-eric. data set. doi: 10.6103/share.w3.500. courgeau d (1973) migrations et découpages du territoire. population [french edition] 28(3): 511–537. esipova n, pugliese a and ray j (2013) the demographics of global internal migration. migration policy practice 3(2): 3–5. jain s and mcdonald p (1997) fertility of australian birth cohorts: components and differentials. journal of the australian population association 14(1): 31–46. kendig h, byles j e, o’loughlin k, nazroo j y, mishra g, noone j, loh v and forder p m (2014) adapting data collection methods in the australian life histories and health survey: a retrospective life course study. bmj open 4(3), http://dx.doi.org/10.1136/bmjopen-2013-004476. kendig h and nazroo j (2016) life course influences on inequalities in later life: comparative perspectives. journal of population ageing 9(1–2): 1–7. long l (1991) residential mobility differences among developed countries. international regional science review 14(2): 133. marmot m, oldfield z, clemens s, blake m, phelps a, nazroo j, steptoe a, rogers n, banks j, oskala a (2016) english longitudinal study of ageing: waves 0–7, 1998–2015. [data collection]. 25th edition. uk data service. sn: 5050, http://doi.org/10.5255/ukda-sn-5050-12. mcdonald p (2017) population ageing: a demographic perspective. in: o'loughlin k, browning c and kendig h (eds) ageing in australia: challenges and opportunities. new york: springer; 41–61. rogers a and castro l j (1981) model migration schedules: a simplified formulation and an alternative parameter estimation method. iiasa working paper wp-81-063. laxenburg, austria: international institute for applied systems analysis. http://dx.doi.org/10.1136/bmjopen-2013-004476 http://doi.org/10.5255/ukda-sn-5050-12 54 bernard a et al. australian population studies 1 (1) 2017 sánchez a c and andrews d (2011) to move or not to move: what drives residential mobility rates in the oecd?. oecd economics department working papers no. 846. paris: oecd publishing, http://dx.doi.org/10.1787/5kghtc7kzx21-en. shyrock h s and larmon e a (1965) some longitudinal data on internal migration. demography 2(1): 579– 592. van arsdol m d, sabagh g and butler e w (1968) retrospective and subsequent metropolitan residential mobility. demography 5(1): 249–267. xu-doeve w l (2006) the measurement of international and internal migration in the 2010 global round of population censuses: twelve key recommendations on questions, concepts and procedures. paper presented at the european population conference of the european association for population studies (eaps), liverpool, united kingdom, 21–24 june 2006. http://dx.doi.org/10.1787/5kghtc7kzx21-en australian population studies 2019 | volume 3 | issue 2 | pages 37-40 © pribesh et al. 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org the flow of family transitions of australian families shana pribesh* old dominion university matthew usevitch baylor college of medicine elizabeth koch sigler brigham young university kaijsa angerhofer heninger brigham young university yuanyuan yue old dominion university mikaela j dufur brigham young university jonathan a jarvis brigham young university * corresponding author. email: spribesh@odu.edu. address: department of educational foundations and leadership, old dominion university, dcoe 2307, norfolk va, usa 23529. paper received 13 june 2018; accepted 14 november 2019; published 18 november 2019 family structure disruption has been linked to negative child educational and health outcomes (perales et al. 2016). australia has relatively stable families, but income disparities between australians are widening, and single-parent families make up a large proportion of families living in poverty. cohabitation is also common in australia with approximately three-quarters of marriages preceded by cohabitation. if substantial family structure churning affects australian children this may expose a need for special policy interventions aimed at family creation and dissolution to ameliorate the negative effects of such stressful experiences. to highlight family structures and transitions australian children experience, we use sankey flow diagrams charting data from ‘growing up in australia: the longitudinal study of australian children (lsac)’ (gilding 2001). we track children from birth to 11 years old using waves 1-6 and population weights to represent 183,521 children born into australian families. we used household rosters to construct three baseline family structures in wave 1 (0-1 years old): biological married, biological cohabit, and biological single. in subsequent waves, we placed children into one of five additional categories if they experienced a family transition:  disrupted biological married – two biological parents who married after the child’s birth and live in the same household.  disrupted non-biological married – two married parents where one parent is not the biological parent of the child (stepfamilies, adoptions, etc.) and the stepparent lives in the same household.  disrupted biological cohabit – two biological parents who began cohabiting after the child’s birth and live in the same household.  disrupted non-biological cohabit – two cohabiting parents where one parent is not the biological parent of the child (social families, etc.) and the social parent lives in the same household.  disrupted single – a single-parent family where a parent exited the family after the child’s birth. d e m o g ra p h ic http://www.australianpopulationstudies.org/ mailto:spribesh@odu.edu 38 pribesh et al. australian population studies 3 (2) 2019 figure 1: paths of family transitions for children who were born to married, cohabiting and single parents australian population studies 3 (2) 2019 pribesh et al. 39 each combination of consecutive family structures defined what we call a family structure path. children with the same family structure path were grouped. we then created sankey diagrams to visualize the most common paths overall based on children’s family structure at birth (figure 1). we include only those paths that represent at least 0.6% of the population. most common family structures and transitions over three-quarters of children were born into a family with biological parents who were married, 16% into a cohabiting parent family, and 7% into a single parent family. while nearly two-thirds of children remained in a family with married biological parents, we discovered 57 distinct family structure paths after birth. but generally, family structures were stable with 75% of children experiencing no transitions and very few children experiencing more than one family transition. six primary paths represented 90% of children. still, 1% of children experienced three or more transitions. among children who experienced at least one transition, 74% were exposed to family instability before age nine. born to married parents children born into families with biological parents who were married experienced the least turbulence with approximately 84% experiencing no family changes. the next most common experience for this group was for the child’s parents to transition from married to a single-parent family representing 9.6% of children born to married parents and 7.4% overall. these two-family experiences make up almost 94 % of all children originally born into families with two biological parents who were married. born to cohabiting parents children who were born into a family with cohabiting parents took 11 distinct paths. the largest path (44%) remained in households with two biological parents who were cohabiting. a fifth of children whose biological parents were cohabiting at the child’s birth then transitioned into marriage. the third largest path in this group consists of children whose parents cohabited at birth but then split up indicating a transition into a single-parent family that persists--a path that represents 15.7% of cohabiters at birth and 2.5% of the total sample. born to a single parent forty-five percent of children born into a single-parent family remained in that path. of the 15 additional paths for children born into single-parent families, the most common was for the single parent to enter a cohabiting relationship. approximately 8% began cohabiting with the biological parent of the child and 15.7% began cohabiting with another person. marriage was less common among those who had a child while single with 7.4% of single parents marrying the biological parent of the child and 6.2% marrying someone else. 40 pribesh et al. australian population studies 3 (2) 2019 references gilding m (2001) changing families in australia. family matters 60: 6-11. perales f, o’flaherty m and baxter j (2016) early life course family structure and children’s socioemotional and behavioural functioning: a view from australia. child indicators research 9: 10031028. waldfogel j, craigie t a and brooks-gunn j (2010) fragile families and child wellbeing. future child 20(2): 87-112. australian population studies 2019 | volume 3 | issue 1 | pages 13-29 © temple, dow and baird 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org special working arrangements to allow for care responsibilities in australia: availability, usage and barriers jeromey temple* university of melbourne; arc centre of excellence in population ageing research briony dow university of melbourne; national ageing research institute marian baird university of sydney; arc centre of excellence in population ageing research * corresponding author. email: jeromey.temple@unimelb.edu.au. address: melbourne school of population and global health, 207 bouverie st, university of melbourne, melbourne, vic, 3010. paper received 17 january 2019; accepted 10 may 2019; published 27 may 2019 abstract background population ageing is projected to reduce labour force growth and aggregate labour force participation, whilst increasing demand for informal carers. increasing the labour force participation of australians who face barriers to employment (including carers) is part of the solution to labour market pressures occurring due to demographic change and may improve the financial wellbeing of carers. aims to examine the availability, usage and barriers to accessing special working arrangements (swa) to provide care while employed in australia. data and methods the 2015 abs survey of disability, ageing and carers was used to measure the prevalence of the availability, usage and barriers to swa to care stratified by carer status and gender. results about 94% of workers reported access to at least one type of swa (n=25,094). of this group, about 22% have used swa to care in the last 6 months. the proportions using swa to care were highest among primary carers (64%) followed by other carers (43%) and non-carers (19%). of those who have used swa, about 15% wanted to use additional swa to care in the previous 6 months, but faced barriers in doing so, with higher proportions of primary carers (24.6%) and other carers (21.8%) reporting barriers. the main barriers faced by employed carers included insufficient paid leave and/or work commitments. conclusions a range of paid and unpaid arrangements are necessary for carers to combine paid work with their caregiving responsibilities. labour market legislation and workplace policies should be strengthened to reduce barriers to take up of swa. key words informal care; caring; labour force participation; barriers to employment; special working arrangements http://www.australianpopulationstudies.org/ mailto:jeromey.temple@unimelb.edu.au australian population studies 3 (1) 2019 temple et al. 14 1. introduction one aspect of population ageing that has garnered significant attention from policy makers is the implications for the australian labour market. both the productivity commission and treasury have noted that population ageing reduces aggregate (i.e. population-level) labour force participation and slows labour force growth (australian treasury 2002, 2007, 2010, 2015; productivity commission 2005, 2013). indeed, the rate of growth in labour supply is projected to decline considerably in the next 15 years, relative to the 15 years proceeding (temple and mcdonald 2017). in recent times, international migration has been key to maintaining labour force growth (mcdonald 2017). however, a further source of increasing labour supply is to improve labour force attachment among australians who face barriers to employment or who are under-employed (temple and mcdonald 2017). increasing labour force attachment of these groups is one part of the solution to declining labour supply growth. one sizable population that faces significant barriers to labour force participation are australian carers, numbering approximately 2.7 million people who contribute 60 billion dollars to the economy annually through unpaid work (abs 2016b; deloitte access economics 2015). with population ageing, the demand for informal care will increase considerably, at the same time that labour supply pressures are occurring in the formal labour market. importantly, the caregiving role has been shown to effect labour force engagement, with australian evidence showing that carers are more likely to reduce hours of work, exit the labour market and earn lower levels of income relative to non-carers (bittman et al. 2007). many female carers in particular have difficulty in accessing flexible working hours, influencing their decision to leave paid work all together (austen and ong 2013). consistent with this finding, hill and colleagues find that with the onset of caring responsibilities, flexible working arrangements (such as part time work), significantly reduced the odds of leaving the paid workforce in australia (hill et al. 2008). a systematic review of 30 years of international studies of caregiving and employment, specifically cites the importance of the further development of labour market legislation and workplace policies (in tandem with formal support services), to enable carers who wish to work, to be able to do so (lilly et al. 2007). australian evidence shows a sizeable proportion of carers wish to work – with about half of those not in paid employment with a preference to be employed (gray et al. 2008). 2. special working arrangements and caring in australia enshrined in the national employment standards of australia’s fair work act, carers, people with a disability, those aged 55 years or over and parents with the responsibility to care for a child have the legal right to request flexible working arrangements from their employer (fwo 2018). although a broad term, flexible working arrangements refer to flexibility in hours of work (e.g. start and finish times), patterns of work (e.g. job sharing or part time work) and location of work (e.g. working from home) (fwo 2018). however, evidence suggests that less than half of all workers are aware of this right (skinner and pocock 2014). moreover, there is no guarantee that the requests for flexible working arrangements are approved by employers or that they are rolled out consistently across australian workplaces (o’loughlin et al. 2017). this is important as the most commonly cited reason given by non-employed caregivers as to why they do not work is difficulty arranging flexible working hours (gray et al. 2008). australian population studies 3 (1) 2019 temple et al. 15 despite the considerable contribution of the above studies to our understanding of the integration of paid work and unpaid caring, there remains a gap in our understanding of the availability, usage and barriers to accessing flexible or special working arrangements (swa) conducive to caring responsibilities. we adopt the terminology swa, consistent with abs data collections and to avoid confusion with one component of swa, flexible working hours. previous studies have focused on either parents with care giving responsibilities, or carers whose recipient has an underlying health condition requiring assistance. in this paper, we examine these aspects of usage of swa by gender in three population groups: (1) primary carers, who provide the principal assistance for a person with a disability or long-term health condition, (2) other carers, who also care for a person with a disability or long-term health condition, but do not provide principal care, and (3) non-carers, who are defined by the australian bureau of statistics (abs) as all people who are not primary or other carers. nonetheless, they may have care responsibilities and a need to access swa, for example, parents and others (e.g. grandparents) with caring responsibilities for children. our interest is in understanding the ways in which people who care have access to, utilise or report barriers to arrangements that enable them to fulfil both their unpaid care work and paid work responsibilities. specifically, with the availability of unique nationally representative data, we seek to answer three questions: (1) what is the level of availability of swas? (2) what is the prevalence of usage of swas specifically to care?, and (3) what are the reported barriers to usage of swas to care? 3. data and methods data for this study were sourced from the 2015 abs survey of disability, ageing and carers (sdac) conducted between july and december 2015 (abs 2016c). three populations were sampled using multi-stage sampling techniques. these consisted of persons living in private dwellings, in self-care retirement villages and in care accommodation. the module on the availability of swa was administered to persons living in households. of 31,957 households originally contacted, 25,555 fully responded, yielding a response rate of 80%. 3.1. measurement of availability, usage and barriers within the employment module of sdac, a number of questions were asked regarding the availability, use and barriers to swas to support caring work. these questions were asked of people aged 15 years and over, living in households and employed, but excluding the self-employed. firstly, respondents were asked “does your employer provide you with any of the following special working arrangements, regardless of whether you have used them or not?” a prompt card was then shown to the respondent, consisting of the following list:  paid leave (e.g. annual leave, maternity leave, sick leave) excluding carer’s leave.  paid carer’s leave  ∙unpaid leave (excluding unpaid carer’s leave) australian population studies 3 (1) 2019 temple et al. 16  unpaid carer’s leave  flexible working hours  rostered day off  working from home  shift work  casual work  part time work  informal arrangement with employer  other (specify)  no special working arrangements available  don’t know. for those indicating the availability of swa, a follow up question was asked: “of those special working arrangements you have mentioned, have you used any to help look after someone in the last six months?” respondents then indicated the swa (from the list above) used to facilitate caring responsibilities and whether there was any unmet need for further access to swa. for those who used swa and indicated a barrier to further access, and those who could not access swa for caring needs at all, a prompt card was used to illicit reasons for this barrier, including:  applied or asked but was refused  do not have adequate working arrangements  didn’t apply as thought they would say no anyway  nature of work makes using flexible working arrangements difficult  work commitments  not paid for time off (e.g., casual/shift worker)  subtle or other pressure from bosses or other workers  not enough paid leave left or available  anything else (specify). 3.2. measurement of carer status using these questions, we develop measures of the availability, usage and barriers to access swa specifically for caring responsibilities. using measures of carer status available in sdac, we examine variations in availability, usage and barriers to swa reported by (1) primary carers, (2) other carers and (3) persons not defined by the abs as carers, but nonetheless have caregiving responsibilities. specifically, a primary carer is defined by the abs as “a person who provides the most informal assistance, in terms of help of supervision, to a person with one or more disabilities, with one or more of the core activities of mobility, self-care or communication” (abs 2016a). other carers are australian population studies 3 (1) 2019 temple et al. 17 defined as one who “provides informal assistance with one or more of the core activity tasks but has not been identified as the person that provides the most informal assistance” (abs 2016a). thus, both primary and other carers are defined with respect to the recipient of care having long term health conditions requiring assistance and care. however, it is not only those who care for people with disabilities or long term health conditions who utilise swa with the specific intent of caring, albeit they are not carers as defined by the abs. this group includes those who have care obligations to others not identified as primary or other carers such as parents with care responsibilities for temporarily sick children or other family members. our analysis seeks to provide population level prevalence of the use of swa to care, thus all three caring categories are included in the following stratified analysis. 4. results figure 1 displays our framework for understanding the availability, usage and barriers to swa for caring using the sdac data. of the full sample of employed people living in households (n=26,529), about 94% report access to at least one type of swa (n=25,094). of this group, about 22% have used swa to care in the last 6 months (n=5,803). of those who have used swa, about 15% wanted to use additional swa to care in the previous 6 months, but faced barriers to do so (n=891). of the 19,291 employed people who did not use swa to care, a small minority wanted to use swa to care but couldn’t (1.2% n=224). 4.1. availability of special working arrangements of the 94% reporting availability of swa, there is considerable variation in the type of swa provided (table 1). within the full working population, the most prevalent swa is paid leave (76%), followed by paid carers leave (48%), unpaid leave (43%) and flexible working hours (39%). when classified by carer status, primary or other carers are more likely to report access to informal arrangements, part time work or unpaid carers leave relative to non-carers. about 5.6% of workers were not aware of the availability of any swa (responding ‘no’ or ‘don’t know’). these data also show important gender differentials with respect to carer status and perceived availability of swa. whereas the gender split for non-carers and other carers are relatively equal, just under 70% of all primary carers are female (68.3%). moreover, although the perceived availability by swa is relatively consistent by gender, females (relative to males) are more likely to cite availability of casual work (32.2% versus 21.5%) or part time work (34.1% versus 14.7%). 4.2. usage of special working arrangements the availability of swa, although important, is distinctly different from usage. results in table 2 classify swa arrangements used in the previous 6 months specifically to care. there is a clear gradient in swa usage to care by carer status. approximately 64% of primary carers had used swa in the previous 6 months, compared with 43% of other carers and about 19% of non-carers. around 2% of primary and other carers wanted to use swa to care but couldn’t. when usage, as opposed to availability of swa is considered, about 55% of non-carers and other carers are female, as are 70% of primary carers. australian population studies 3 (1) 2019 temple et al. 18 figure 1: framework of the availability, usage and barriers to swa for caring source: designed by the authors; data from abs 2016c consistent with the data on availability (table 1), the results in table 2 show that paid leave (42%) and paid carers leave (47%) are the most commonly used swa to care. about 10% of primary carers report unpaid leave, unpaid carers leave, casual work or part-time work swa to care – which is higher than the rates of usage by non-carers. about one quarter of primary carers also cite use of flexible working hours to care (24%). again, there is relative consistency in the likelihood of using different swa to care by gender. for example, about 15.1% of males who have used swa to care have used flexible work hours as have 17% of females. however, although rates of usage are similar for males and females, the usage of specific swa to care is heavily skewed towards female workers. for example, around 80% of those using part-time work to care are female, regardless of carer status. among primary carers specifically, around 80% of those using part-time work, casual work, or unpaid carers leave to care are female, regardless of carer status. australian population studies 3 (1) 2019 temple et al. 19 table 1: availability of special working arrangements (%) by carer status and sex, 2015 males females total % female carer status total carer status total carer status total carer status total access to swa no primary other no primary other noprimary other noprimary other no 4.2 2.9 3.9 4.1 3.6 3.0 4.4 3.7 3.9 2.9 4.2 3.9 45.6 68.5 53.6 46.8 don’t know 2.0 1.0 2.8 2.0 1.5 0.3 0.8 1.4 1.7 0.5 ** 1.8 1.7 42.7 40.8 22.5 40.9 yes 93.9 96.1 93.2 93.9 94.8 96.7 94.8 94.9 94.3 96.5 ** 94.0 94.4 49.2 68.4 50.9 49.9 total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 48.9 68.3 50.5 49.7 type of swa has access to: paid leave 79.9 72.1 81.1 79.8 73.1 70.0 76.6 73.3 76.6 70.7 ** 78.8 * 76.6 47.0 67.7 49.5 47.8 paid carer's leave 47.7 43.5 50.4 47.8 48.2 48.8 54.8 48.8 47.9 47.1 52.7 *** 48.3 49.5 70.8 53.0 50.4 unpaid leave 42.7 41.0 42.2 42.6 43.7 44.0 48.1 44.1 43.2 43.1 45.2 ** 43.3 49.8 69.9 54.2 50.8 unpaid carer's leave 29.2 30.0 32.4 29.5 30.3 34.5 37.0 31.1 29.8 33.1 * 34.8 ** 30.3 50.1 71.3 54.2 51.2 flexible working hours 37.2 42.6 37.8 37.3 41.1 44.9 45.1 41.6 39.1 44.2 *** 41.5 *** 39.5 51.7 69.5 55.3 52.6 rostered day off 24.6 23.7 25.7 24.6 20.1 15.0 23.0 20.1 22.4 17.7 ** 24.3 * 22.4 44.2 57.7 48.1 44.9 working from home 19.0 20.3 19.9 19.1 17.3 18.4 20.1 17.6 18.2 19.0 20.0 ** 18.3 47.0 66.2 51.1 48.0 shift work 17.3 13.7 19.4 17.4 14.9 10.9 16.1 14.8 16.1 11.7 *** 17.7 16.1 45.4 63.2 46.2 45.9 casual work 21.6 21.9 20.0 21.5 32.4 30.3 31.1 32.2 26.9 27.6 25.7 26.8 59.2 74.9 61.8 59.9 part time work 14.5 19.7 15.9 14.7 32.8 46.3 41.5 34.1 23.5 37.9 *** 29.0 *** 24.4 68.6 83.6 73.0 69.8 informal arrangement 9.2 14.9 11.8 9.5 9.7 16.1 15.3 10.4 9.4 15.8 *** 13.5 *** 10.0 50.5 70.1 57.4 52.2 other 1.0 1.7 0.8 1.0 0.8 0.7 1.3 0.8 0.9 1.0 1.1 0.9 43.0 47.3 62.6 45.1 n= 11974 263 1120 13357 11456 558 1158 13172 23430 821 2278 26529 na na na na % total (weighted) 89.9 1.9 8.2 100.0 87.4 4.1 8.5 100.0 88.7 3.0 8.4 100.0 48.9 68.3 50.5 49.7 source: abs 2016c notes: swa special working arrangements; nobase case for tests of proportions for the total category; * p<0.05 **p<0.01 ***p<0.001; % females percentage in each discrete category that are female; na not applicable. australian population studies 3 (1) 2019 temple et al. 20 table 2: whether used special working arrangements to care (%) by carer status and sex, 2015. males females total % female carer status total carer status total carer status total carer status total used swa to care? no primary other n= no primary other n= noprimary other noprimary other wanted to, but couldn't 0.7 2.7 1.1 0.8 103 0.9 2.3 1.9 1.0 121 0.8 2.4 ** 1.5 ** 0.9 53.7 65.0 63.1 55.9 no need 81.8 36.1 58.9 79.0 9838 77.1 31.9 49.9 72.9 9019 79.5 33.2 *** 54.3 *** 76.0 47.8 65.7 46.8 48.0 don't know 0.8 0.8 1.4 0.8 110 0.7 0.2 0.8 0.7 100 0.8 0.4 ** 1.1 0.8 47.0 35.6 38.1 45.7 yes, used 16.7 60.5 38.5 19.3 2503 21.3 65.7 47.4 25.4 3300 19.0 64.0 *** 43.0 *** 22.3 55.3 70.2 56.1 56.8 total 100 100 100 100 12554 100 100 100 100 12540 100 100 100 100 type of swa used to care: paid leave 42.2 42.4 42.0 42.2 1019 43.3 37.4 37.1 41.7 1326 42.8 38.9 39.3 ** 41.9 56.0 67.5 53.1 56.5 paid carer's leave 48.5 40.4 49.6 48.2 1218 46.1 42.0 50.9 46.4 1566 47.2 41.5 * 50.3 47.2 54.1 71.0 56.7 55.8 unpaid leave 4.3 9.7 6.6 5.0 123 7.8 9.6 7.7 8.0 246 6.2 9.6 * 7.3 6.7 69.4 69.9 59.9 67.8 unpaid carer's leave 1.9 7.0 5.7 2.8 65 3.4 10.4 6.7 4.7 146 2.7 9.4 *** 6.2 *** 3.9 68.5 77.8 60.0 68.3 flexible working hours 14.5 25.8 16.4 15.5 375 15.1 24.6 20.7 17.0 553 14.8 25.0 *** 18.8 ** 16.3 56.4 69.2 61.7 59.1 rostered day off 4.7 13.0 10.8 6.2 134 2.7 3.9 6.1 3.4 98 3.6 6.6 * 8.1 *** 4.6 41.5 41.3 41.9 41.6 working from home 9.7 13.3 8.7 9.7 224 7.8 7.5 7.2 7.6 241 8.6 9.2 7.9 8.5 49.9 56.8 51.3 50.7 shift work 1.4 2.0 1.3 1.4 33 1.0 1.2 1.2 1.1 35 1.2 1.4 1.2 1.2 48.3 58.3 53.5 50.2 casual work 4.1 7.1 4.7 4.4 101 6.3 12.7 6.0 6.9 212 5.3 11.0 *** 5.4 5.8 65.4 80.7 61.9 67.4 part time work 1.3 5.5 1.6 1.6 45 6.2 11.6 4.8 6.6 219 4.0 9.8 *** 3.4 4.4 85.3 83.3 78.9 84.2 informal arrangement 3.5 7.2 5.4 4.0 90 3.0 6.9 3.2 3.4 106 3.2 7.0 * 4.2 3.7 51.4 69.2 43.1 52.8 other 0.7 1.6 0.0 0.6 11 0.3 0.0 0.6 0.3 9 0.5 0.5 0.3 0.5 36.6 0.0 100.0 40.8 source: abs 2016c notes: swa special working arrangements; nobase case for tests of proportions for the total category; * p<0.05 **p<0.01 ***p<0.001; % females percentage in each discrete category that are female; n= unweighted sample count. australian population studies 3 (1) 2019 temple et al. 21 4.3. barriers to special working arrangements referring back to figure 1, of the 5,803 workers who indicated they had used swa to care, about 15.5% (n=891) reported they wanted to use more but were unable to. this group were asked what swa they wanted to use but couldn’t (table 3). once more, paid leave and paid carers leave were the most likely swa that workers wished to make more use of to care. interestingly, there is little difference in the swa type needed by carer status. however, primary carers (24.6%) and other carers (21.8%) were more likely to report a barrier to further use of swa, relative to non-carers (13.1%). types of swa needed are relatively consistent by gender. however, male other carers are more likely to cite the need for rostered day off (11.8% versus 2.5%) whereas female other carers are more likely to cite the need for paid leave (34.7% versus 23.9%). again, due simply to the overrepresentation of female primary carers, about 70% of primary carers with unmet demand for further access to swa were female. results in table 4 report the reasons for barriers to using swa to care, for two groups. the first ‘additional use of swa’ are the 15.5% (n=891) group who used swa, but wanted to use more and couldn’t. regardless of carer status, the main reasons for not using further swa to care were ‘not enough paid leave left’ (29%), ‘work commitments (23.4%) and ‘nature of work makes using flexible working arrangements difficult’ (16%). although in the minority, it is concerning to note that 8% cited ‘subtle or other pressures from bosses or other workers’ or ‘didn’t apply as thought they would say no anyway’. primary carers were slightly more likely to cite this later reason (12%) compared with non-carers. the second group in table 4, titled ‘any use of swa’ are those who had swa available to them, but could not use it to care at all. referring back to figure 1, this is the smaller group of 1.2% (n=224) of those who didn’t use swa to care. as with the previous group, about 1 in 4 report ‘work commitments’ as the main reason for not using swa to care (24.3%). approximately 15% reported ‘didn’t apply as thought they would say no’, ‘nature of work makes using flexible working arrangements difficult’ or ‘subtle or other pressure from bosses or other workers’. due to the small sample size of this population, there are few statistically significant differences in reasons given for barriers to any use of swa by carer status. moreover, there is insufficient sample size to disaggregate this table by gender. australian population studies 3 (1) 2019 temple et al. 22 table 3: unmet demand for further access to special working arrangements to care (%) by carer status and sex, 2015. males females total % female carer status total carer status total carer status total carer status total more use of swa? no primary other n= no primary other n= noprimary other noprimary other no 83.2 66.2 69.5 79.9 2010 84.6 69.6 75.9 81.6 2694 83.9 68.6 *** 73.1 ** 80.9 55.9 71.3 58.4 57.4 don’t know 3.1 8.3 5.9 3.9 96 2.8 6.3 4.4 3.4 112 2.9 6.9 ** 5.1 ** 3.6 52.6 64.2 49.1 53.8 yes 13.7 25.5 24.5 16.2 397 12.6 24.1 19.7 15.0 494 13.1 24.5 *** 21.8 *** 15.5 53.5 69.1 50.7 55.0 total 100 100 100 100 2503 100 100 100 100 3300 100 100 100 100 type of swa needed paid leave 36.6 36.1 23.9 33.4 131 35.0 32.5 34.7 34.5 163 35.7 33.6 29.4 34.0 52.4 66.8 60.0 55.8 paid carer's leave 42.6 37.4 39.8 41.4 170 42.6 44.8 44.1 43.3 221 42.6 42.5 42.0 42.4 53.5 72.8 53.3 56.1 unpaid leave 2.0 10.1 5.9 3.7 15 5.5 2.4 4.6 4.8 25 3.9 4.8 5.3 4.3 76.5 34.8 44.4 61.3 unpaid carer's leave 1.8 8.1 1.4 2.3 9 3.9 10.1 3.9 5.0 19 2.9 9.5 2.7 3.8 71.3 73.6 74.5 72.6 flexible working hours 10.4 4.0 8.5 9.3 43 7.2 13.5 8.2 8.5 48 8.7 10.6 8.3 8.9 44.4 88.2 49.9 52.7 rostered day off 1.0 6.4 11.8 4.2 13 1.0 2.1 2.5 1.5 8 1.0 3.4 7.1 ** 2.7 52.7 42.1 18.0 30.3 working from home 8.3 4.5 11.8 8.8 35 6.6 6.2 4.7 6.2 32 7.4 5.7 8.2 7.4 47.7 75.7 29.3 46.0 shift work 0.5 2.8 1.3 0.9 4 0.2 1.3 0.0 0.3 2 0.3 1.8 0.7 0.6 26.0 50.5 0.0 29.4 casual work 2.5 1.2 5.6 3.2 12 4.7 2.8 4.7 4.4 18 3.7 2.3 5.1 3.8 67.9 84.4 46.7 62.8 part time work 0.0 2.1 1.4 0.5 3 1.1 3.4 1.8 1.6 13 0.6 3.0 1.6 1.1 100.0 78.4 57.6 78.7 informal arrangement 1.5 0.7 1.1 1.3 6 1.7 1.7 0.3 1.4 8 1.6 1.4 0.7 1.4 56.2 84.0 20.2 56.0 other 0.2 0.0 0.0 0.1 1 0.1 0.0 0.0 0.0 1 0.1 0.0 0.0 0.1 27.5 0.0 0.0 27.5 source: abs 2016c notes: swa special working arrangements; nobase case for tests of proportions for the total category; * p<0.05 **p<0.01 ***p<0.001; % female percentage in each discrete category that are female; n= unweighted sample count. australian population studies 3 (1) 2019 temple et al. 23 table 4: reasons for barrier to additional or any use of special working arrangements (%) by carer status, 2015. additional use of swa [1] any use of swa [2] carer status all carer status all reason for barrier no primary other no primary other applied or asked but was refused 5.4 8.1 4.0 5.4 8.0 15.0 8.6 8.6 do not have adequate working arrangements 9.2 6.2 10.1 9.0 5.9 6.6 15.0 7.2 didn't apply as thought they would say no anyway 6.7 11.9 * 9.0 7.9 15.0 23.9 11.1 15.1 concern that using arrangements would be viewed poorly 0.9 1.0 0.0 * 0.7 0.1 0.0 3.7 0.6 nature of work makes using flexible working arrangements difficult 15.2 16.5 16.9 16.0 14.7 15.2 21.8 15.5 work commitments 22.3 30.6 # 22.0 23.4 24.9 33.9 15.0 24.3 not paid for time off (e.g. casual/shift worker) 6.6 5.2 8.2 6.8 8.8 9.9 21.0 # 10.6 subtle or other pressure from bosses or other workers 7.0 12.1 8.1 8.0 14.1 7.3 9.9 13.0 not enough paid leave left or available 31.0 26.2 25.2 29.0 6.7 18.3 10.8 8.2 own circumstances made use of arrangements unfeasible 1.3 0.0 ** 2.9 1.5 3.3 0.9 0.0 * 2.7 anything else 3.9 3.4 3.7 3.8 7.7 7.0 8.2 7.7 don't know 5.8 5.0 6.5 5.9 8.9 4.9 0.8 7.5 n 573 128 190 891 170 18 36 224 source: abs 2016c notes: swa special working arrangements; nobase case for tests of proportions; # p<0.10 * p<0.05 **p<0.01 ***p<0.001; n= unweighted sample count; [1] population of those who had already used swa, but have unmet demand for further use of swa to care; [2] population of those who have not used swa and wanted to use them to care. australian population studies 3 (1) 2019 temple et al. 24 5. discussion the clear majority of respondents reported the availability of swa in their workplace (94%) and indeed, carers were slightly more likely to cite awareness of flexible working hours, unpaid carers leave, part time work and informal arrangements with their employer than non-carers. it may be that carers are more aware of certain swa, because of their personal requirement to have them as a necessary condition of employment. that is, they self-select into positions with swa that enable a continuation of unpaid caring responsibilities. a further explanation is that they are more aware of swa regardless of occupation or industry, simply because they have a greater need for swa than non-carers. swa are taken up by a majority of primary carers (64%) and 43% of other carers (within the last six months) with paid leave and paid carers leave being the most used arrangements. however, these arrangements are not perceived as sufficient for 15.5% of the workforce surveyed, with primary carers (24.6%) and other carers (21.8%) more likely to report barriers to further use of swa than non-carers (13.1%). the majority of unmet demand is by those who already use it, but need to make more use of it. supporting previous research, our results underscore the gendered nature of care giving responsibilities in australia and show the interaction with swa usage. almost 70% of employed primary carers using swa to care were female, compared with 55% of other and non-carers. around 80% of those using part-time work to care were female, regardless of carer status. among primary carers specifically, around 80% of those using part-time work, casual work, or unpaid carers leave to care are female, regardless of carer status. while there has been considerable attention on the needs of mothers for flexible work arrangements in australia, our results also highlight the un-met needs of workers who provide care for those with a disability and long-term health problems. women also overwhelming attend to these various care needs, altering their work schedules to do so and experiencing negative consequences in terms of career and financial penalties. these findings regarding carers are supported by a growing body of research and data points to both the gendered use of swas in the general population (i.e. not just carers), including part-time work, and the gap between availability of swas and their uptake. mcdonald et al.(2005 p.41) argue that men, and women in managerial roles, are less likely to use swas due to lack of managerial support, perceptions of negative career consequences, lack of co-worker support and time pressures at work. in a study of a large telecommunications company, cooper and baird (2015) found that use of australia’s legislative right to request ‘flexible work arrangements’ was heavily dominated by working mothers when they were supported by their line managers. in a comparative review, thornthwaite (2004) shows that working mothers, more than fathers, in australia prefer part-time work and access to flexible hours to accommodate the gendered division of labour in the home, school hours and lack of suitable child care. for both male and female carers, the main barrier that carers face is insufficient paid leave and/or work commitments (requiring them to put the demands of the workplace over their need for time off to care) but to a lesser extent they face subtle or real pressure from others not to apply for leave or other flexible work arrangements. around 5% of those who wanted to access further swa for care and 9% of those who wanted to access any swa cited a rejection by the employer. australian population studies 3 (1) 2019 temple et al. 25 under the national employment standards, employers can refuse a request on ‘reasonable business grounds’. these grounds are very broad and include:  requested arrangements are too costly for the employer  there is no capacity to change the current working arrangements  impractical to change extant working arrangements  the requested arrangement would result in a ‘significant loss of efficiency or productivity’  the requested arrangement would be likely to have a significant negative impact on customer service. in the case of a refused request, the employee can seek assistance from the fair work commission. however, the fair work commission does not have the legislative power to direct an employer to agree to the employee’s request. therefore, there is limited right to appeal the employers’ refusal. moreover, there are numerous caveats to those eligible to access flexible arrangements under the act. for example, workers must have been employed for at least 12 months before making a request for flexible working arrangements. stronger legislative controls have recently come into force following a ruling from the full bench of the fair work commission. from 1 december 2018, employers must provide a detailed written response outlining the reason for the refused request. in considering the request, employers must consider (1) the needs of the employee, (2) consequences for the employee is changes in working arrangements aren’t made, as well as (3) reasonable business grounds for refusing the employees request (fwo 2019). rather than being considered as part of labour market policy alone, access to flexible working arrangements for carers should be seen as an integral part of the health system supporting australia’s ageing population and those with underlying health conditions (yeandle and cass 2013; vecchio 2015). indeed, in vecchio’s (2015) important study of the labour force behaviour of those residing with a person with a disability, they argue “policy makers need to aggressively challenge current workforce programs to encourage employers to provide more flexible work arrangements. workforce programs that allow family members opportunities to provide adequate caregiving and financial support to ill relatives are fundamental to the sustainability of health care programs” (p. 9). there is currently no overarching policy framework in australia that addresses this issue. there was a national carer strategy in australia (2011) but this was not adopted by the current government. the previous labor federal government commenced the implementation of a national carer action plan 2011-2014, which had a range of strategies for improving the economic security of carers, including strategies for enabling workforce participation. however, the current coalition government has restricted its focus to carers to carer support services accessible through the carer gateway (department of social services 2017). with the role out of the national disability insurance scheme (ndis), early evidence suggests that carers employment prospects have not improved (hamilton 2018). one possibility is to allow carers access to ndis to support employment needs. as argued by hamilton (2018) “this would be an important start in developing services that actually support carers to work – not just hoping that carers gain time for paid work by altering disability services”. australian population studies 3 (1) 2019 temple et al. 26 in interpreting the results from this study, it is important to note the limitations. first, data from the sdac are cross-sectional and the measures are collected only for the employed. we cannot, for example, determine whether carers have ceased employment due to a lack of flexible working arrangements, although evidence suggests this may be the case (austen et al. 2013). secondly, our measure of the usage of swa is retrospective, over a six month period only. third, the analyses we present herein are descriptive. further multivariable analysis is required, particularly of the industry, workplace and characteristics of carers reporting a barrier to accessing swa to care. 6. conclusions with the ageing of the australian population, there is a need for more family carers at the same time as for greater workforce participation, especially amongst women. this study suggests that to enable people to deliver their caregiving responsibilities and participate in the workforce, more paid leave is required as well as other swa strategies that encourage employers to recognize and support carers in the workplace. the business case for offering swa is growing, with a number of large employers now offering ‘flex for all’. mcdonald et al. (2005 p. 38), citing a number of studies, outline the benefits for business as ‘improving the retention or recruitment of skilled women, reducing absenteeism, increasing productivity and reducing hiring and retraining costs’. there are also numerous coted benefits to employees of being able to access swas. these include reduction in personal stressors and improvements in the mental and physical health of workers (mcdonald et al. 2005 p. 39). given that financial considerations are among the strongest unmet needs reported by australian carers, improving the fit between paid and unpaid work is one strategy by which improvements in economic wellbeing can be achieved (temple and dow 2018). more generally, greater awareness of the societal and economic benefits of caring are needed so that workplace arrangements are not just seen as an individual benefit and carers can feel legitimized in accessing swa. stronger legislative arrangements are also required to enforce employers to grant carers flexible working arrangements. recent strengthening of legislative controls have recently come into force following a ruling from the full bench of the fair work commission and will require evaluation with further data collections. another possible solution would be government subsidies to enable carers to take more leave. whatever policy and practice levers are put in place, thorough evaluation is required to improve knowledge of which swa are effective in enabling carer workforce participation. key messages  population ageing and demographic change are increasing the number of unpaid informal carers who face barriers to labour market attachment at the same time that the australian labour market is projected to experience lower growth and reduced participation.  many australian carers face barriers to employment, as well as barriers to underemployment by those already employed. although the vast majority of workers are aware of swa and about 1 in 5 have used swa to care, almost 1 in 4 primary carers and 1 in 5 other carers faced barriers to using swa to care. australian population studies 3 (1) 2019 temple et al. 27  the main barriers faced by employed carers included insufficient paid leave and/or work commitments (requiring them to put the demands of the workforce over their need for time off to care).  the results also underscore the gendered nature of care responsibilities in australia. almost 70% of employed primary carers using swa to care were female, compared with 55% of other and non-carers. among primary carers specifically, around 80% of those using part-time work, casual work, or unpaid carers leave to care were female.  stronger legislative arrangements are required to assist carers to access swa. acknowledgements data for this study were made available to the authors by the australian bureau of statistics (abs). jeromey temple is funded by the australian research council’s centre of excellence in population ageing research (ce1101029). the opinions expressed herein are those of the authors alone. references abs (2016a) disability, ageing and carers, australia: summary of findings. catalogue no. 4430.0. canberra: abs. available from: https://www.abs.gov.au/ausstats/abs@.nsf/mf/4430.0. accessed may 2018. abs (2016b) a profile of carers in australia. information sheet. canberra: abs. available from: https://www.abs.gov.au/ausstats/abs@.nsf/lookup/4430.0main+features602015. accessed may 2018. abs (2016c) microdata: disability, ageing and carers, australia, 2015. catalogue no. 4430.0.30.002. canberra: abs. austen s and ong r (2013) the effects of ill health and informal care roles on the employment retention of mid-life women: does the workplace matter? journal of industrial relations 55(5): 663-680. australian treasury (2002) intergenerational report 2002-03. canberra: australian government. australian treasury (2007) intergenerational report. canberra: australian government. australian treasury (2010) intergenerational report. australia to 2050: future challenges. canberra: australian government. australian treasury (2015) intergenerational report: australia in 2055. canberra: australian government. bittman m, hill t and thomson c (2007) the impact of caring on informal carers’ employment, income and earnings: a longitudinal approach. australian journal of social issues 42(2): 255-272. cooper r and baird m (2015) bringing the 'right to request' flexible working arrangements to life: from policies to practices. employee relations 37 (5): 568-581. cummins r, hughesj, tomyn a, gibson j, woerner j and lai, ll. 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calculating a deprivation index using census data paul norman* university of leeds laurie berrie university of leeds daniel j exeter university of auckland * corresponding author. email: p.d.norman@leeds.ac.uk. address: school of geography and leeds institute for data analytics, university of leeds, leeds ls2 9jt, united kingdom paper received 30 october 2018; accepted 4 april 2019; published 27 may 2019 abstract background deprivation indexes have widespread use in academic research and in local and national government applications. it is useful for people to understand their construction and to be able to calculate their own measures. aims we provide an overview of the background to area based deprivation measures. we detail and explain a series of steps taken to calculate a deprivation index for small areas in australia. data and methods we use data from australia’s 2016 census of population and housing for the sa2 level of geography. after defining the set of variables used as inputs, we emulate the steps taken to calculate other census based deprivation indexes. results the resulting scheme correlates closely with an official, but more sophisticated deprivation measure, suggesting that simple schemes have utility. conclusions there are choices to be made for input variables and for some of the detail of the calculations. researchers can follow the steps we describe to develop their own measures. key words area deprivation; composite measures; small areas; census http://www.australianpopulationstudies.org/ mailto:p.d.norman@leeds.ac.uk australian population studies 3 (1) 2019 norman, berrie & exeter 31 1. introduction the use of area deprivation indexes is widespread across academic research and in local and national government applications (allik et al. 2016). the australian bureau of statistics produce socioeconomic indexes for areas (seifa) using census data, which includes the index of relative socioeconomic disadvantage (irsd). the latest version uses 2016 census data. our aim here is to demonstrate a method of calculation to people, such as academic and local government researchers, who may be new to the production of composite measures. following sections on generic aspects, this paper steps through the process of creating a deprivation index using census data for small areas (sa2s) in australia for 2016. we take a similar approach to the calculation steps used in the long-established townsend (townsend et al. 1988) and carstairs (carstairs and morris 1989) indexes. we compare the deprivation index calculated here with the seifa irsd. we provide data files so that researchers can reproduce the deprivation index and believe the method used here to be accessible to quantitative population geographers new to this kind of work who will then be able to construct their own composite measures. these measures might focus on particular dimensions of deprivation or be for other purposes for which a combination of indicator variables are applicable. 2. what is deprivation? deprivation is one of those things which we probably think we understand until we tried to define it! townsend's (1987 p. 125) definition is commonly used: “deprivation may be defined as a state of observable and demonstrable disadvantage relative to the local community or the wider society or nation to which an individual, family or group belongs. the idea has come to be applied to conditions (that is, physical, environmental and social states or circumstances) rather than resources and to specific and not only general circumstances, and therefore can be distinguished from the concept of poverty”. defining poverty itself is far from easy (paterson and gregory 2019). from a eurocentric perspective, deprived areas are places in which concentrations of people and households with the relevant characteristics exist. 3. what is a deprivation index? a deprivation index provides a single figure estimate of the level of deprivation for each location within the study area. since deprivation is both hard to define and cannot be directly measured, the index is a latent construct calculated using a combination of indicator variables believed to capture relevant dimensions. having a single figure per area simplifies applications that use the index compared to using multiple variables. the deprivation index value for any one area is usually expressed relative to a larger study region, often the national level (fu et al. 2015). 4. which variables should be used as inputs? as noble et al. (2006 p. 172) point out, if a researcher is devising their own index, there should first be a clear theoretical foundation underpinning the notion of small area deprivation, which may then 32 norman, berrie & exeter australian population studies 3 (1) 2019 be operationalised as an index. deprivation indexes have their roots in census-based work in the uk, first by holtermann (1975) and subsequently by townsend (1987) and others. we cannot turn back the clock, but speculate that there may not have been the same motivation to construct deprivation indexes had the uk, unlike many other countries, included an income question in the census (dorling 1999; boyle and dorling 2004). thus, deprivation indexes in the uk use ‘proxy’ indicators of income and other dimensions of social and/or material hardship. unemployment is ubiquitously included in schemes but there is variation in further variables used as inputs (see senior 2002). in countries such as australia, canada and new zealand, where income-related questions are asked, measures of individual and/or household income are components of their deprivation indexes. the researcher needs to obtain variables which best represent particular aspects of deprivation to ensure the index is fit for purpose. the set of chosen variables should complement each other so that the index is ‘greater than the sum of its parts’. the availability of potential variables for inclusion will be affected by decisions on the geographic unit used (below). being based on data from a census, schemes are cross-sectional (though see the paper’s concluding section). to an extent there will be overlap of the facets chosen to proxy aspects of deprivation and likely to be strong interrelationships. since the purpose is to identify multiple deprivation this collinearity may not be an issue. however, an index calculated in the manner described here would tend to have a few key variables. a more multi-dimensional approach would need a technique such as principal components analysis (noted again below). 5. which geography should be used? most deprivation indexes are devised for small areas (sub local government). as above, since the roots of schemes lie in the uk and the census has been the main source of data, then census geographies have tended to be used. initially, within england and wales, the most common geographical units used were the electoral wards (mackenzie et al. 1998), while the carstairs index, originally developed for scotland, used postal sectors. these geographies were typically chosen in order to ensure that the count of people in each ward/sector was greater than 100, thus minimising the amount of missing / suppressed data. people are often motivated to develop an index for the smallest possible areas, to aid regeneration targeting, for example. if the aim is to relate to geographical health variations, then a geography which represents people’s day-to-day lives might be more suitable. ideally, the researcher would choose the geography which best suited the relevant situation. in reality, researchers may well not have the freedom of choice of geography they might wish for, as the smallest unit for which the desired indicators are available may also dictate the level of analysis. it is important to note that all results will be affected by the specification of the zones which are used (openshaw and taylor 1981; flowerdew et al. 2008). 6. a small area deprivation index for australia we now continue with the specifics involved with developing a small area deprivation index for australia. norman et al. (2016) calculated a measure of changing deprivation using data from the 2001 and 2011 censuses in australia. we will incorporate similar variables here for a cross-sectional australian population studies 3 (1) 2019 norman, berrie & exeter 33 deprivation index for 2016. the geography will be the statistical areas level 2 (sa2s). whilst not the smallest census geography, the sa2s are local level areal units for which detailed australian bureau of statistics data are released, including tables for geographic areas by a variety of person and household attributes. sa2s generally have populations between 3,000 and 25,000 persons with an average population of around 10,000 (abs 2017). 6.1. choose a set of indicator variables table 1 lists the variables we use. these have been chosen to represent a range of deprivation dimensions: unemployment (haynes et al. 1996); low income (d’ambrosio and frick 2007); lack of good english (bertotti et al. 2012); low educational achievement (wilkinson and pickett 2007) and; lone parents (santana 2002). these are here as examples and each can be substituted or there can be additional variables should a researcher wish to use different indicators. table 1: input variables from the 2016 census in australia (sa2) 2016 census table number & title variable input to index g04 ‘age by sex’ count of persons g13 ‘language spoken at home by proficiency in spoken english language by sex’ % persons who do not speak english well g16 ‘highest year of school completed by age by sex’ % persons not completing school to year 10 g29 ‘total household income (weekly) by household composition’ % households with income less than $1,500 (median income is $1,438) g39 ‘dwelling structure by household composition and family composition’ % dwellings with lone parent households g43 ‘labour force status by age by sex’ % persons unemployed source: australian bureau of statistics note: the variables expressed as a percentage are numerator / denominator x 100. the variables listed in table 1 have been obtained from the table number stated. the numerators and denominators are sourced from the same tables so that appropriate percentages can be calculated. the inputs used for these are included in this article’s online resources (noted at the end of the paper). the percentages represent variables whereby the higher the percentage, the greater the level of the deprivation. the polarity of the variables needs to be consistent. 6.2. excluding areas with very small populations in 2016 there were 2,301 sa2s in australia but since some have very small populations, we only include those with 200 or more persons so the deprivation index developed is for 2,169 sa2s. researchers could combine an area with a small population with an adjacent area so as not to lose data. 6.3. transforming and standardising the input variables many social variables have skewed distributions and researchers may choose to transform input variables to (near) normal distributions. the townsend index, for example, log transforms the 34 norman, berrie & exeter australian population studies 3 (1) 2019 percentages of unemployment and overcrowding as these are positively skewed. the need for, and methods of transformations, are subject to debate (gilthorpe 1995; senior 2002). for simplicity, we do not transform variables here. there is more of a consensus on the need to standardise variables. underpinning the need for this step is that each of the input variables will have differences in what are inherently large and small values. for example, at the sa2 level, the percentage of persons not completing school to year 10 varies between 4.02% and 70.42% with a mean of 20.00, whereas the percentage of lone parents varies between 2.16% and 36.05% with a mean of 10.96. there is a need to have variables on a comparable scale. the most common method (as used in both the townsend and carstairs schemes) is to standardise using z-scores. the inputs to the z-score calculation for the sa2 variables are the percentages of each variable. the resulting z-scores for all variables have a mean of zero and a standard deviation of 1 so they are now comparable. higher positive z-scores are higher levels of the indicator and more negative values are lower levels. z-scores are calculated using the formula: z-score = (observation mean) / standard deviation alternatively, the ‘range standardisation’ calculation can be used (lucy and burns 2017). range standardisation rescales observations for a variable to lie between 0 and 1. 6.4. combining the standardised input variables the aim is to have a single figure deprivation index and a regular approach is to sum the z-scores of the input variables. a simple ‘additive’, unweighted approach is used in the townsend and carstairs indexes so that all variables contribute equally. the jarman index (1983) applies weights to differentially change the impact of inputs when they are summed. in reality, the weights applied by jarman more likely reflect gp workload rather than a variable’s ability to better measure deprivation (senior 2002). for deprivation in australia, we sum the five sets of z-scores unweighted to thereby have a deprivation index for the sa2 geography. once summed, in terms of interpretation, more positive index scores reflect higher levels of deprivation and more negative values are lower levels of deprivation. since the indicators aim to capture deprivation, areas found to lack deprivation should not be described as relatively wealthy or affluent. an alternative method of combining a set of indicator variables is to use principal components analysis. the new zealand index of deprivation for 2013 used nine census-derived variables of deprivation and the weights of the first principal components are used to combine the nine variables into an overall deprivation score (atkinson et al. 2014). the seifa / irsd in australia also uses principal components analysis (abs 2018a). 6.5. categorising into quantiles index scores themselves have great utility, but many applications use the scores categorised into quantiles. it is common to use quintiles or deciles whereby the distribution is divided into fifths or tenths. often this is based on the number of areas or sometimes on the count of persons so that australian population studies 3 (1) 2019 norman, berrie & exeter 35 there would be an equal number of areas or persons in each category. the impact of differently defined categorisations has had little coverage in the literature (compared with discussions of transformation and standardisation). the use of ‘population weighted’ quantiles has become common and is what we adopt here. the quantile cut-offs partition the deprivation distribution into categories with (near) equal numbers of people in each (table 2). table 2: counts of persons in each deprivation quantile deciles persons percent quintiles persons percent q1 (least deprived) 2,337,625 10.01 q1 (least deprived) 4,671,384 20.01 q2 2,333,759 9.99 q3 2,333,735 9.99 q2 4,668,398 19.99 q4 2,334,663 10.00 q5 2,336,028 10.00 q3 4,672,799 20.01 q6 2,336,771 10.01 q7 2,327,819 9.97 q4 4,660,545 19.96 q8 2,332,726 9.99 q9 2,332,560 9.99 q5 (most deprived) 4,677,180 20.03 q10 (most deprived) 2,344,620 10.04 total 23,350,306 100.00 total 23,350,306 100.00 source: based on australian bureau of statistics data 7. comparison of the deprivation index with an existing scheme the australian bureau of statistics produce socio-economic indexes for areas (seifa), which includes the index of relative socio-economic disadvantage (irsd). the most recent version uses 2016 census data. note that there is a difference in polarity from the census measure we have developed here, so a low irsd score indicates relatively greater disadvantage whereas a high score indicates a relative lack of disadvantage (abs 2018b). the deprivation index developed in our analysis correlates -0.933 with the irsd suggesting that the two schemes identify similar patterns of (non-) deprivation. a cross-tabulation of deciles from both schemes also demonstrates fair similarity in the categorisation of areas (table 3). table 3: cross-tabulation of the deprivation index and seifa irsd quantiles deprivation index deciles q1 (least) q2 q3 q4 q5 q6 q7 q8 q9 q10 (most) total se if a ir sd q1 (most) 0 0 0 0 0 0 0 1 46 169 216 q2 0 0 0 0 0 1 25 49 111 31 217 q3 0 0 0 0 7 24 52 90 40 5 218 q4 0 0 0 9 25 52 67 43 21 1 218 q5 0 0 3 20 53 75 40 25 2 1 219 q6 0 0 11 63 70 49 18 6 0 0 217 q7 2 13 70 71 41 15 4 0 0 1 217 q8 4 65 93 34 15 4 1 0 0 0 216 q9 48 112 47 7 2 0 1 1 1 0 219 q10 (least) 177 34 1 0 0 0 0 0 0 0 212 total 231 224 225 204 213 220 208 215 221 208 2169 source: based on australian bureau of statistics data 36 norman, berrie & exeter australian population studies 3 (1) 2019 8. conclusion we have developed a deprivation index for the australian sa2 geography using five indicators derived from the country’s 2016 census. we have taken similar steps to those used to calculate the townsend and carstairs indexes by calculating percentages of the variables, which are then standardised and summed (unweighted) to form a single figure deprivation index. we categorise the deprivation scores into deciles and quintiles. the similarity between an index produced in this relatively simple way with the more sophisticated seifa irsd is consistent with previous findings in australia (norman et al. 2016). researchers wishing to develop their own indexes and make choices on geographic scale and input variables should be able to follow the same steps. it could be that an input to an existing scheme is regarded by others as an outcome of deprivation so there is a need for an index without that variable. the imd for england includes a health indicator so there is risk of a self-fulfilling prophecy if relationships between deprivation and health are investigated (adams and white 2004). exeter et al. (2017) overcame this by providing a version of the imd for new zealand which removes a domain (i.e. imd no health) and redistributes the weights for the remaining six domains to reduce issues associated with data circularity. a composite index for a different application can be developed using relevant inputs. see, for example, congdon (2004) on an index of social fragmentation and lucy and burns (2017) on an index of loneliness. two aspects will be relevant to people wanting to build on this work relating to alternative data sources or extending from cross-sectional measures to those which capture changing deprivation. a variety of deprivation schemes now use administrative data sources (e.g. noble et al. 2006; exeter et al. 2017). with a move away from reliance on census data, the same approach as we use here can have administrative data inputs. a scheme for england (ajebon and norman 2016) using a small number of administrative variables as inputs relates closely to both a census derived measure as well as the more sophisticated, multiple domain imds (noble et al. 2006) now in common usage. census-based deprivation schemes are specific to the period of census data collection and administrative schemes for the year they are released (but may be based on inputs for different time points). all these are cross-sectional. however, areas change over time in their characteristics so increasingly researchers are interested in capturing this. examples of methods and applications can be found in norman (2010), exeter et al. (2011; 2019), norman et al. (2016), pearce et al. (2016), norman (2016), green et al. (2017), norman and darlington-pollock (2017) and shackleton et al. (2018). 9. resources we provide an excel file of the raw input variables plus commented files of spss syntax, stata do and r script so that people can reproduce the process we have described above. a working knowledge of these packages is needed. the files can be accessed via: http://dx.doi.org/10.17632/k957gctr9d.1. http://dx.doi.org/10.17632/k957gctr9d.1 australian population studies 3 (1) 2019 norman, berrie & exeter 37 key messages  this introductory guide explains the background concepts relating to area deprivation and to data and geography choices.  the calculation of a deprivation index is stepped through and explained.  researchers are provided with a set of resources through which to reproduce the process.  researchers are encouraged to develop their own small area indexes. acknowledgements we are grateful for the feedback from two anonymous referees. references allik m, brown d, dundas r and leyland a h (2016) developing a new small-area measure of deprivation using 2001 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1965-1978. australian population studies 2017 | volume 1 | issue 1 | pages 26–40 © raymer, biddle and guan 2017. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org a multiregional sources of growth model for school enrolment projections james raymer* the australian national university nicholas biddle the australian national university qing guan the australian national university *corresponding author. email: james.raymer@anu.edu.au. address: school of demography, anu college of arts and social sciences, the australian national university, 9 fellows road, acton act 2601, australia paper received 9 may 2017; accepted 17 july 2017; published 20 november 2017 abstract background education planning requires accurate and efficient projection models. current projection models either do not make use of all available information and are reliant on idiosyncratic expert judgement, or are too complex to be maintained and explained. aims to test whether a multiregional projection model performs better than current methodology in explaining and projecting school enrolments in a school system with student mobility. data and methods a multiregional cohort model was developed for projecting enrolments for multiple schools or districts simultaneously. for illustration, data were obtained for all government schools in the australian capital territory (act) for the years 2008–2016. multiregional projections were compared with a cohort transition model and the act education directorate’s own projections. results (i) there is great diversity in the sources of school enrolment growth that need to be accommodated in enrolment projections; and (ii) multiregional projections perform slightly better than traditional methods with less effort and more transparency. conclusion a sources of growth approach guides the understanding of enrolment change, which is critical for making informed projections. key words enrolment projections; cohort transition; multiregional demography; australian capital territory; australia. http://www.australianpopulationstudies.org/ mailto:james.raymer@anu.edu.au australian population studies 1 (1) 2017 raymer j, biddle n and guan q 27 1. introduction school districts require information about the expectation of future school enrolments so that they can plan the supply of classrooms, teachers, materials and facilities. school enrolments are also important for understanding the education system within a larger social and economic context (stone 1965). without accurate projections, education may be disrupted because of inadequate facilities or a lack of teachers or other resources. alternatively, education may be over-budgeted in the provision of teachers, infrastructure and resources, thus causing a misallocation of public funds. while projections are never entirely certain due to unobserved factors influencing student mobility decisions (morrison 2000), there are a variety of demographic tools that can be applied to increase projection certainty and help better judgements to be made. surprisingly, in our review we find that most education jurisdictions neglect investments in testing or improving projection methodology and instead rely on relatively crude projection models with ad-hoc assumptions built in. in this paper, we assess a method to project future enrolments for multiple schools or school districts simultaneously. our method is illustrated with data obtained for the australian capital territory (act) from the act education directorate for the period 2008–2016. our aim is to provide better understanding of the demographic drivers enrolment change, and to develop more efficient projection systems. the multiregional projections are designed to study transitional changes that have occurred over time across school levels, as well as between schools and school regions. 2. review of methods used to project school enrolments sweeney and middleton (2005, p. 366) list several distinct approaches used to project school enrolments. these include cohort survival and regression methods that use past enrolment data and birth records, as well as extended versions of these methods which incorporate other information such as migration and student drop-out rates. they also list the modifiable spatial filter method (rushton, armstrong and lolonis 1995), which combines cohort survival methods with residential address data to determine the size of future school attendance areas. these methods can incorporate birth records, past and future housing unit data and the number of students each housing type yields. webster (1971) provides a similar list of projection approaches but also includes those based directly on age-specific population counts. johnstone (1974) further distinguishes between models that are deterministic (including markov chain models), stochastic and constrainable. one key issue is whether projections should be focused at the school level or at the broader district level. this also applies to projections for subgroups in heterogeneous populations (grip 2009). a bottom-up (school level) approach can be tailored to fit each school’s composition and needs; however, this approach may not consider wider demographic changes in the region around the school. a top-down (district level) approach, on the other hand, is often considered pragmatic because projections for large areas tend to be more accurate and less prone to rapid population changes (berk & associates 2008; grip 2009; schellenberg and stephens 1987, p. 13; stronge and schultz 1981; swanson and tayman 2012, p. 281). it can also incorporate wider demographic changes which are occurring in the region of interest. the main disadvantage is that a top-down approach may produce unrealistic results for schools which have trends or student profiles that are substantially different from other schools within their district. 28 raymer j, biddle n and guan q australian population studies 1 (1) 2017 in order for projections to be understood and utilised, the methodology and assumptions need to be transparent and replicable. the projection approach must also be flexible and able to be adapted to a variety of situations and changes that occur to enrolment patterns if the time-consuming process of developing specific projection models for each school or school district is to be avoided (gould 1993; johnstone 1974; stone 1965). this includes schools in established neighbourhoods, as well as those in areas that are currently being developed or planned. at times, it may be necessary to incorporate expert judgements or scenarios to account for future change possibilities (morrison 2000). furthermore, the projection methodology should be regularly assessed in terms of accuracy (how well it predicts the truth) and efficiency (amount of time and effort required to produce results) (swanson and tayman 2012). in most developed countries, including australia, there tends to be very high rates of grade progression (close to 100 per cent) in most schools. this implies the expectation that, for example, nine years from now nearly all students enrolled in academic level 1 today will be enrolled somewhere in level 10. moreover, there tends to be high retention of students at particular schools. the exception, of course, is for students transitioning between primary and secondary school or, in jurisdictions such as the act, from a government high school (years 7 to 10) to a secondary college (years 11 and 12). current bulges or dips in student numbers can be expected to move through the academic levels over time. if primary school enrolments are lower in one year, secondary or high school enrolments will follow at predictable times in the future. projections for new schools require a relational model where auxiliary information such as births, population projections, household composition and anticipated migration is used to estimate the long-term stable size and composition of future student enrolments. there are other situations where auxiliary information is also needed. for example, newly developed areas in middle or outer growth precincts may be expected to first attract young families with preschool and primary school aged children due to the relative affordability of land or housing for newly established household units. over time, these children will progress through the school system, with the school eventually reaching a steady state in respect to the number of new and continuing enrolments (herrick 1952). one approach which has not been considered widely in projecting future education requirements is a multiregional or multistate population model, which is an extension of the cohort transition model. multiregional population models provide a general and flexible platform for modelling and analysing subnational population change over time (rogers 1975, 1995; land and rogers 1982; schoen 1988). they enable the combination of all the main components of population change by age with various transitions that each population group may experience over the life course. these transitions may be between academic levels (including primary to secondary or high school or high school to a secondary college) or between government and non-government schools. despite the many theoretical and analytical advantages, multiregional models have been relatively unexplored because of the large amount of input data needed and requirement for matrix calculations to perform the projections and analyses. one exception is sweeney and middleton (2005), who applied a multiregional cohort enrolment projection method to better understand intradistrict school mobility and evaluate existing enrolment projections in santa barbara, california. their aim was to understand intra-district school transfers in an open enrolment system for a heterogeneous population. in this paper, we build on their ideas to improve school enrolment projections in the act. australian population studies 1 (1) 2017 raymer j, biddle n and guan q 29 3. analysing the sources of enrolment change the population of the act has grown substantially over the past decade and a half from 322,000 in 2001 to 398,000 in 2016 (act government 2017). this growth has been driven both by natural increase and net internal migration. net internal migration contributed only a small amount despite large flows as levels of in-migration tended to offset out-migration. the act’s average annual population growth rate between 2001 and 2014 was 1.4 per cent with a peak of 2.2 per cent occurring in the 2006–2007 period. the act has seven population regions: belconnen, gungahlin, north canberra, south canberra, weston creek, woden valley and tuggeranong.1 the relatively new region of gungahlin, located in canberra’s north, experienced the most rapid growth during this time, increasing from 25,000 in 2001 to 62,000 in 2014 with an average annual population growth rate of 7.4 per cent. in australia, like in many other federal systems, school planning is undertaken at the state or territory level. the act is considered a geographically small system by australian standards with four main levels of public school-based education: • preschool – the level before full-time schooling, denoted as level p • primary school – the first seven years of full-time schooling, referred to as level k (kindergarten) to level 6 • high school – the next four years of full-time schooling, or levels 7 to 10 • secondary college – the last two years of full-time schooling, or levels 11 and 12. the percentage of students in the act attending a government school increased from 57.5 per cent in 20082 to 59.6 per cent in 20163. the remainder were in the non-government school sector, with transitions between both systems as documented in this paper. the act education directorate is responsible for 88 public schools in the act comprising six early childhood schools (i.e., preschool to level 2), 51 primary schools (some with preschools attached), 10 high schools, nine combined primary/high schools, eight secondary colleges and four specialist schools. 4 record-level data from 2008 to 2016 taken at each year’s census in february were provided for this study. the data represents 611,674 student observations and contains the following variables: student id (anonymised); census date; school; academic level (levels p–12); suburb; state. from these data, the transitions between academic levels were calculated, as well as movements amongst schools for all students in the act. following rees and willekens (1986), data were obtained that could be used to identify the main sources of enrolment change. this accounting framework is outlined in table 1. the variable gij represents internal migration events from one school region i to another school region j. internal migration events are excluded when i = j. instead, terms ri are entered, which are accounting balances that capture the result of subtracting all possible exit events from the starting enrolment population. 1 note, for our analyses, the canberra central region is divided into north canberra and south canberra. a map of the schools and regions is available from http://www.education.act.gov.au/__data/assets/pdf_file/0005/73319/160210-actpublic-schools-map-2016.pdf 2 http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/ffbe2ce6d8296d21ca2576ea0011f617?opendocument 3 http://www.abs.gov.au/ausstats/abs@.nsf/detailspage/4221.02016?opendocument 4 http://www.education.act.gov.au/publications_and_policies/publications_a-z/annual_report/annual-report-20152016/section-b/b.1-organisational-overview. specialist schools are excluded from this study. http://www.education.act.gov.au/__data/assets/pdf_file/0005/73319/160210-act-public-schools-map-2016.pdf http://www.education.act.gov.au/__data/assets/pdf_file/0005/73319/160210-act-public-schools-map-2016.pdf http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/ffbe2ce6d8296d21ca2576ea0011f617?opendocument http://www.abs.gov.au/ausstats/abs@.nsf/detailspage/4221.02016?opendocument http://www.education.act.gov.au/publications_and_policies/publications_a-z/annual_report/annual-report-2015-2016/section-b/b.1-organisational-overview http://www.education.act.gov.au/publications_and_policies/publications_a-z/annual_report/annual-report-2015-2016/section-b/b.1-organisational-overview 30 raymer j, biddle n and guan q australian population studies 1 (1) 2017 this number represents students who transition to the next academic level while remaining in the school region. total internal out-migration from each school region are denoted by gi+ and total internal in-migration to each school region are denoted by g+j. the ii variable signifies the number of migration events from outside the system of interest and oi tabulates the corresponding number of persons leaving the system of interest. mi and ni denote transfers from and to non-government schools, respectively. the graduation events, xi, and preschool, bi, complete the flows in the table. note, in this table, persons who leave the school system without graduating are included in oi. table 1: a sources of growth accounting framework for government school enrolments across regions destination region region (t+1) (t) 1 2 3 4 5 6 7 ng mig grad total 1 r1 g12 g13 g14 g15 g16 g17 m1 o1 x1 te1 2 g21 r2 g23 g24 g25 g26 g27 m2 o2 x2 te2 3 g31 g32 r3 g34 g35 g36 g37 m3 o3 x3 te3 4 g41 g42 g43 r4 g45 g46 g47 m4 o4 x4 te4 5 g51 g52 g53 g54 r5 g56 g57 m5 o5 x5 te5 6 g61 g62 g63 g64 g65 r6 g67 m6 o6 x6 te6 7 g71 g72 g73 g74 g75 g76 r7 m7 o7 x7 te7 p b1 b2 b3 b4 b5 b6 b7 0 0 0 b+ ng n1 n2 n3 n4 n5 n6 n7 0 0 0 n+ mig i1 i2 i3 i4 i5 i6 i7 0 0 0 i+ total 1 1 +te 1 2 +te 1 3 +te 1 4 +te 1 5 +te 1 6 +te 1 7 +te m+ o+ x+ notes: (1) definitions of variables and subscripts: e = school enrolment population; r = balancing terms; g = internal migrations (within the act); p (b) = preschool enrolments; ng (m, n) = transfer to/from non-government schools; mig (o, i) = migration to/from other states within australia or overseas; grad (x) = exits due to graduation from government schools; 0 = structural zeroes; t = time; i = subscript for region; and + = summation over regions. (2) assumes zero deaths. the sum of the numbers in the rows of table 1 add up to the enrolments at the beginning of the time interval, t ie . the balancing term is obtained by subtracting the total number of migrations to other regions within the act, transfers to non-government schools, migrations to places outside the act, and graduations from the population at the beginning of the time interval, i.e., 𝑟𝑟𝑖𝑖 = 𝑒𝑒𝑖𝑖𝑡𝑡 − 𝑔𝑔𝑖𝑖+ − 𝑜𝑜𝑖𝑖 − 𝑚𝑚𝑖𝑖 − 𝑥𝑥𝑖𝑖 similarly, the variables in the columns of table 1 add up to the enrolments at the end of the time interval. we can compute these by adding to the balancing term the total in-migrations, migrations from outside the act, transfers from non-government schools and preschool entrants, i.e., 𝑒𝑒𝑖𝑖𝑡𝑡+1 = 𝑟𝑟𝑖𝑖 + 𝑔𝑔+𝑖𝑖 + 𝑖𝑖𝑖𝑖 + 𝑛𝑛𝑖𝑖 + 𝑏𝑏𝑖𝑖 if we combine these two equations, the balancing term cancels out and we obtain the components of school enrolment change: 𝑒𝑒𝑖𝑖𝑡𝑡+1 = 𝑒𝑒𝑖𝑖𝑡𝑡 − 𝑔𝑔𝑖𝑖+ − 𝑜𝑜𝑖𝑖 − 𝑚𝑚𝑖𝑖 − 𝑥𝑥𝑖𝑖 + 𝑔𝑔+𝑖𝑖 + 𝑖𝑖𝑖𝑖 + 𝑛𝑛𝑖𝑖 + 𝑏𝑏𝑖𝑖 thus, the information described in table 1 provides the basis for understanding the sources of enrolment change from one year to the next at the region level. australian population studies 1 (1) 2017 raymer j, biddle n and guan q 31 consider table 2, which contains the sources of growth and cohort transitions occurring across school regions in the act for levels p–11 in 2015 to levels k–12 in 2016. the row sums equal the p–11 enrolments for schools in each of the seven act regions. the column sums equal the corresponding k–12 enrolments one year later. between 2015 and 2016, 72,694 students made a transition. this included 5,393 students who moved out of the act and 6,387 students who moved to the act. over 80 per cent of the transitions occurred within the seven regions, with non-government schools having the highest retention. the proportion of students leaving government schools between 2015 and 2016 in the act ranged from 5.6 per cent in weston creek to 10.8 per cent in woden valley. in-migration was greatest to non-government schools (n=2,142), followed by gungahlin (n=823), belconnen (n=788) and north canberra (n=696). table 2: sources of enrolment change and cohort transition proportions for school regions in the act: levels p–11 (2015) to levels k–12 (2016) region enrolment region 2016 2015 gun bel scan tugg wod west ncan ng mig total enrolment change gun 5,635 84 21 8 9 6 55 332 628 6,778 bel 124 8,582 27 18 20 12 124 331 722 9,960 scan 12 17 3,455 32 145 3 14 129 392 4,199 tugg 33 32 22 6,010 146 38 32 346 706 7,365 wod 14 11 47 98 3,177 21 132 152 441 4,093 west 8 4 10 33 121 1,612 22 77 112 1,999 ncan 56 88 89 21 19 2 4,319 144 558 5,296 ng 190 133 140 214 125 30 128 23,823 1,834 26,617 mig 823 788 576 526 609 169 754 2,142 0 6,387 total 6,895 9,739 4,387 6,960 4,371 1,893 5,580 27,476 5,393 72,694 transition proportions gun 0.831 0.012 0.003 0.001 0.001 0.001 0.008 0.049 0.093 1.000 bel 0.012 0.862 0.003 0.002 0.002 0.001 0.012 0.033 0.072 1.000 scan 0.003 0.004 0.823 0.008 0.035 0.001 0.003 0.031 0.093 1.000 tugg 0.004 0.004 0.003 0.816 0.020 0.005 0.004 0.047 0.096 1.000 wod 0.003 0.003 0.011 0.024 0.776 0.005 0.032 0.037 0.108 1.000 west 0.004 0.002 0.005 0.017 0.061 0.806 0.011 0.039 0.056 1.000 ncan 0.011 0.017 0.017 0.004 0.004 0.000 0.816 0.027 0.105 1.000 ng 0.007 0.005 0.005 0.008 0.005 0.001 0.005 0.895 0.069 1.000 mig 823 788 576 526 609 169 754 2,142 0 6,387 notes: gun = gungahlin; bel = belconnen; scan = south canberra; tugg = tuggeranong; wod = woden valley; west = weston creek; ncan = north canberra; ng = act non-government schools; mig = migration to/from other states within australia or overseas. next, consider the cohort transitions presented in table 3 (next page) from level 10 to level 11. the diagonal elements represent those who remained in schools within the region and progressed from level 10 to level 11. most regions retained the majority of their students in the transition from high school to secondary college, except weston creek (0 per cent, where no secondary college is available) and woden valley (46%). tuggeranong had the highest retention (83%). the data clearly show that substantial movements occurred across school regions in the transition from high school to secondary college. 32 raymer j, biddle n and guan q australian population studies 1 (1) 2017 table 3: cohort transition proportions for school regions in the act: level 10 (2015) to level 11 (2016) region enrolment region 2016 2015 gun bel scan tugg wod west ncan ng mig total gun 0.807 0.048 0.013 0.000 0.003 0.000 0.033 0.008 0.090 1.000 bel 0.056 0.789 0.016 0.004 0.007 0.000 0.047 0.005 0.074 1.000 scan 0.010 0.005 0.829 0.025 0.005 0.000 0.005 0.020 0.101 1.000 tugg 0.009 0.009 0.018 0.826 0.055 0.000 0.000 0.005 0.078 1.000 wod 0.006 0.006 0.091 0.360 0.457 0.000 0.000 0.000 0.080 1.000 west 0.013 0.000 0.046 0.119 0.722 0.000 0.013 0.007 0.079 1.000 ncan 0.038 0.077 0.162 0.031 0.198 0.000 0.396 0.018 0.080 1.000 ng 0.048 0.023 0.043 0.042 0.026 0.000 0.016 0.747 0.055 1.000 mig 67 99 78 95 161 0 72 87 0 659 notes: gun = gungahlin; bel = belconnen; scan = south canberra; tugg = tuggeranong; wod = woden valley; west = weston creek; ncan = north canberra; ng = act non-government schools; mig = migration to/from canberra. gungahlin tuggeranong north canberra figure 1: components of enrolment change for schools in gungahlin, tuggeranong and north canberra, 2008–2016 -1200 -800 -400 0 400 800 1200 2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15 2015-16 -1500 -500 500 1500 2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15 2015-16 -1000 -500 0 500 1000 2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15 2015-16 preschool enrolments graduates net migration within act net migration from outside act move to non-government schools net gain australian population studies 1 (1) 2017 raymer j, biddle n and guan q 33 between 2008 and 2016 most school regions in the act, except tuggeranong, experienced growth in enrolments each year. the sources and levels of enrolment change, however, varied considerably across the regions with some regions dependent on several sources of growth (e.g., south canberra, woden valley and non-government schools) and others driven primarily by preschool enrolments (e.g., belconnen, tuggeranong and weston creek). consider, for example, the sources of enrolment change during 2008–2016 for schools in the gungahlin, tuggeranong and north canberra regions (figure 1, previous page). gungahlin grew the most, with this growth particularly evident from 2011 with 500 to 560 new students added each year. preschool enrolments were the most significant and increasing component of growth for gungahlin. however, there was a steady net loss of students to non-government schools each year. preschool enrolments similarly were the only source of enrolment growth in the tuggeranong region between 2008 and 2016, declining marginally in 2015–2016. 4. cohort transition projection models three models are introduced for projecting enrolments by academic level in this section. the first is the standard cohort transition model based on annual enrolment numbers by academic level (johnstone and philp 1973; gould 1993; webster 1970). the second projection model is a multiregional cohort transition model that integrates all of the main sources of enrolment change presented in table 1. the third projection model is that utilised by the act education directorate, which, at the individual school level, combines cohort transition information with assumptions on household compositional changes over time in relation to planned developments in the school’s priority intake area. feedback from school principals on the plausibility of the results is also incorporated. to assess the accuracy of the projections, 2008–2012 data are used to predict the observed 2013– 2016 enrolments with the assumption that preschool enrolments are known. the purpose of the analysis is to see how well the two types of data-based projections perform against the act education directorate’s projections. 4.1 cohort transition model a simple and effective way to project school enrolments is to calculate the ratios of students progressing from one academic level to the next. while this does not explain changes to enrolment numbers from one year to the next, it does provide a measure of the overall change, which can be compared over longer periods. consider, for example, the observed enrolment data for schools in the gungahlin region from 2008– 2016 (table 4). here, we see that there were 316 level 1 students in 2008 (shaded grey). in 2009, this cohort of students grew to 325 level 2 students and then to 341 level 3 students in 2010. in 2016, the same cohort represented 385 level 9 students. note, as mentioned previously, gungahlin is a relatively new school region and has been growing rapidly due to migration from outside the act (level 11 became available in 2011 and led to the first cohort of level 12 students in 2012). cohort sizes in other school regions remained very similar or declined. 34 raymer j, biddle n and guan q australian population studies 1 (1) 2017 table 4: observed enrolment data by academic level for schools in gungahlin, 2008–2016 level 2008 2009 2010 2011 2012 2013 2014 2015 2016 p 589 543 579 619 633 736 815 888 898 k 361 402 379 432 516 538 613 699 773 1 316 373 423 397 460 549 580 586 693 2 326 325 346 429 428 471 531 570 598 3 335 331 341 378 433 443 485 553 553 4 296 350 360 316 401 459 468 494 575 5 309 318 357 350 350 423 461 497 521 6 309 303 319 349 390 380 440 485 502 7 242 273 284 264 339 339 332 387 458 8 229 259 266 295 278 354 360 367 392 9 204 231 260 271 284 298 365 380 385 10 203 204 245 261 289 321 316 399 415 11 0 0 0 308 369 413 502 479 570 12 0 0 0 0 303 311 396 489 458 notes: p = preschool; k = kindergarten. transition ratios calculated from the enrolment numbers in table 4 can be used to produce projections of school enrolments. the projection model is specified, in matrix form, as 𝐄𝐄𝑡𝑡+1 = 𝐆𝐆𝐄𝐄𝑡𝑡 + 𝐁𝐁 where 𝐄𝐄𝑡𝑡 are vectors denoting enrolments at time t and in academic level x, g is the transition matrix and b is a vector including the projected preschool enrolments. in detailed form, the matrix equation looks like ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡𝑒𝑒𝑃𝑃 𝑡𝑡+1 𝑒𝑒𝐾𝐾𝑡𝑡+1 𝑒𝑒1𝑡𝑡+1 𝑒𝑒2𝑡𝑡+1 𝑒𝑒3𝑡𝑡+1 𝑒𝑒4𝑡𝑡+1 𝑒𝑒5𝑡𝑡+1 𝑒𝑒6𝑡𝑡+1 𝑒𝑒7𝑡𝑡+1 𝑒𝑒8𝑡𝑡+1 𝑒𝑒9𝑡𝑡+1 𝑒𝑒10𝑡𝑡+1 𝑒𝑒11𝑡𝑡+1 𝑒𝑒12𝑡𝑡+1⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔𝑃𝑃 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔𝐾𝐾 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 𝑔𝑔11 0⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡ 𝑒𝑒𝑃𝑃 𝑡𝑡 𝑒𝑒𝐾𝐾𝑡𝑡 𝑒𝑒1𝑡𝑡 𝑒𝑒2𝑡𝑡 𝑒𝑒3𝑡𝑡 𝑒𝑒4𝑡𝑡 𝑒𝑒5𝑡𝑡 𝑒𝑒6𝑡𝑡 𝑒𝑒7𝑡𝑡 𝑒𝑒8𝑡𝑡 𝑒𝑒9𝑡𝑡 𝑒𝑒10𝑡𝑡 𝑒𝑒11𝑡𝑡 𝑒𝑒12𝑡𝑡 ⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ + ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡𝑏𝑏 𝑡𝑡–4𝑔𝑔0 0 0 0 0 0 0 0 0 0 0 0 0 0 ⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ where 𝑒𝑒𝑥𝑥𝑡𝑡 denotes enrolments at time t, 𝑔𝑔𝑥𝑥 denotes transitions between school levels with the subscript marking the origin academic level, 𝑏𝑏𝑡𝑡–4 denotes births and g0 is the ratio of births at time t–4 to preschool enrolments. this model could be adapted further to include repetition rates as in johnstone and philp (1973). australian population studies 1 (1) 2017 raymer j, biddle n and guan q 35 4.2 multiregional cohort transition model the enrolment transition model presented above is designed for projecting enrolments for single regions/schools independent of other regions/schools. to allow multiple regions/schools to be projected simultaneously, the matrix projection model needs to be reworked to include transitions amongst schools as well as academic levels. this matrix projection model is specified as: et+1,x+1 = get,x+ix+1 where et,x is a vector of enrolments of regions or schools at time t and academic level x, g contains the transition probabilities between levels and schools (gij), and ix+1 is a vector of in-migration counts of enrolments at academic level x+1. in detailed form, the matrix equation for an eight school region system looks like ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡𝑒𝑒1,𝑥𝑥+1 𝑡𝑡+1 𝑒𝑒2,𝑥𝑥+1 𝑡𝑡+1 𝑒𝑒3,𝑥𝑥+1 𝑡𝑡+1 𝑒𝑒4,𝑥𝑥+1 𝑡𝑡+1 𝑒𝑒5,𝑥𝑥+1 𝑡𝑡+1 𝑒𝑒6,𝑥𝑥+1 𝑡𝑡+1 𝑒𝑒7,𝑥𝑥+1 𝑡𝑡+1 𝑒𝑒8,𝑥𝑥+1 𝑡𝑡+1 ⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ = ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡ 𝑟𝑟1 𝑔𝑔21 𝑔𝑔31 𝑔𝑔41 𝑔𝑔51 𝑔𝑔61 𝑔𝑔71 𝑔𝑔81 𝑔𝑔12 𝑟𝑟2 𝑔𝑔32 𝑔𝑔42 𝑔𝑔52 𝑔𝑔62 𝑔𝑔72 𝑔𝑔82 𝑔𝑔13 𝑔𝑔23 𝑟𝑟3 𝑔𝑔43 𝑔𝑔53 𝑔𝑔63 𝑔𝑔73 𝑔𝑔83 𝑔𝑔14 𝑔𝑔24 𝑔𝑔34 𝑟𝑟4 𝑔𝑔54 𝑔𝑔64 𝑔𝑔74 𝑔𝑔84 𝑔𝑔15 𝑔𝑔25 𝑔𝑔35 𝑔𝑔45 𝑟𝑟5 𝑔𝑔65 𝑔𝑔75 𝑔𝑔85 𝑔𝑔16 𝑔𝑔26 𝑔𝑔36 𝑔𝑔46 𝑔𝑔56 𝑟𝑟6 𝑔𝑔76 𝑔𝑔86 𝑔𝑔17 𝑔𝑔27 𝑔𝑔37 𝑔𝑔47 𝑔𝑔57 𝑔𝑔67 𝑟𝑟7 𝑔𝑔87 𝑔𝑔18 𝑔𝑔28 𝑔𝑔38 𝑔𝑔48 𝑔𝑔58 𝑔𝑔68 𝑔𝑔78 𝑟𝑟8 ⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡𝑒𝑒1,𝑥𝑥 𝑡𝑡 𝑒𝑒2,𝑥𝑥 𝑡𝑡 𝑒𝑒3,𝑥𝑥 𝑡𝑡 𝑒𝑒4,𝑥𝑥 𝑡𝑡 𝑒𝑒5,𝑥𝑥 𝑡𝑡 𝑒𝑒6,𝑥𝑥 𝑡𝑡 𝑒𝑒7,𝑥𝑥 𝑡𝑡 𝑒𝑒8,𝑥𝑥 𝑡𝑡 ⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ + ⎣ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎡ 𝑖𝑖1,𝑥𝑥+1 𝑖𝑖2,𝑥𝑥+1 𝑖𝑖3,𝑥𝑥+1 𝑖𝑖4,𝑥𝑥+1 𝑖𝑖5,𝑥𝑥+1 𝑖𝑖6,𝑥𝑥+1 𝑖𝑖7,𝑥𝑥+1 𝑖𝑖8,𝑥𝑥+1⎦ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎤ , where the diagonal elements of the g matrix is equal to the retention proportions (ri) and the offdiagonal elements capture the movements between schools or regions (gij). this model is similar to the one used by sweeney and middleton (2005) to study enrolment transfers in the santa barbara elementary school district in california. 5. school enrolment projections 5.1 school regions to provide an assessment of different projection models, we first focus on school regions. this allows us to make broad comparisons regarding expectations of change across a range of schools, and to work with data that tend to be more stable over time and less prone to specific situations that require expert assumptions or local knowledge. for the assessment, we assume that preschool enrolments are known. normally these are estimated using observed or projected birth data (t–4). in addition to our comparison of the two projection models against the act education directorate’s projections and the observed data, we show the effects of different assumptions concerning the transitions used for the projections. the enrolment transition projection model uses the average annual transitions from 2008–2012. three different transitions assumptions are used in the multiregional projection model. the first keeps 2011–2012 transitions constant. the second uses average 2008–2012 transitions and holds them constant. the third incorporates trends based on linear regressions of the observed transitions from 2008–2009 to 2011–2012. 36 raymer j, biddle n and guan q australian population studies 1 (1) 2017 table 5: average observed and projected student enrolments by school region, 2013–2016 multiregional school region observed ed cohort transition 2011–12 2008–12 trend gun 6,941 7,195 6,229 6,663 5,971 6,911 bel 10,464 10,683 10,652 10,340 10,636 10,443 scan 4,633 4,766 4,517 4,501 4,471 4,789 tugg 7,942 7,873 7,756 8,181 7,985 8,304 wod 4,548 4,280 4,325 4,354 4,247 4,476 west 2,063 2,178 2,083 2,071 2,041 2,210 ncan 5,628 5,724 5,637 5,690 5,511 5,860 total 42,219 42,699 41,198 41,799 40,861 42,994 notes: gun = gungahlin; bel = belconnen; scan = south canberra; tugg = tuggeranong; wod = woden valley; west = weston creek; ncan = north canberra; ed = act education directorate. table 5 presents the average 2013–2016 results from the school region projections with the best performance shaded grey. overall, the multiregional projection model with 2011–2012 transitions performed the best, followed closely by the act education directorate’s projections. however, the performance for each model varied by school region: • the act education directorate’s projection model did well on average for the tuggeranong school region (-0.9% error), but poorly for gungahlin (3.7%), woden valley (-5.9%) and weston creek (5.6%). • the enrolment transition method performed the best out of all the models for south canberra (-2.4%) and north canberra (0.2%), well for weston creek (0.9%) but poorly for gungahlin (9.9%) and woden valley (-5.2%). • the multiregional model with 2011–2012 transitions performed well for weston creek (0.4%) but poorly for gungahlin (-4.5%) and woden valley (-4.5%). • the multiregional model with 2008–2012 transitions performed well for tuggeranong (0.5%) and weston creek (-1.1%), but very poorly for gungahlin (-14.6%) and poor for woden valley (-6.9%). • the multiregional model with trend transitions did very well for gungahlin (-0.5%) and belconnen (-0.2%), but not well for south canberra (3.5%), tuggeranong (4.5%), weston creek (7.2%) and north canberra (4.2%). the year-to-year projection results and observed enrolment numbers for gungahlin, tuggeranong and north canberra are presented in figure 2 (next page). in summary, the multiregional models applied to school regions appear to work best overall (especially considering the objective nature of the information required). average transition models work well when the school regions are relatively stable but poorly when regions are growing, such as gungahlin and belconnen. here, incorporating trends or auxiliary information on planning developments in the transitions makes sense. the big advantage of the multiregional projection models is that the patterns of change (and error) can be explained and linked to observed trends. there is also consistency in the projection framework for school region moves within the act. that is, a departure from one school region must be an entry into another. this is particularly important when considering the transition between primary and high school levels and between high school and secondary college levels. the other factor to consider is efficiency. australian population studies 1 (1) 2017 raymer j, biddle n and guan q 37 gungahlin tuggeranong north canberra figure 2: observed and estimated enrolments for schools in gungahlin, tuggeranong and north canberra, 2008–2016 notes: act ed = act education directorate’s projection; ct = cohort transition; mr = multiregional projection; obs = observed values. 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500 8,000 2008 2009 2010 2011 2012 2013 2014 2015 2016 act ed ct mr 11-12 mr 08-12 mr trend obs 7,500 7,700 7,900 8,100 8,300 8,500 8,700 8,900 9,100 9,300 9,500 2008 2009 2010 2011 2012 2013 2014 2015 2016 act ed ct mr 11-12 mr 08-12 mr trend obs 4,900 5,100 5,300 5,500 5,700 5,900 6,100 6,300 2008 2009 2010 2011 2012 2013 2014 2015 2016 act ed ct mr 11-12 mr 08-12 mr trend obs % error mr 11-12 1.1 act ed 1.8 mr 8-12 -3.5 ct 0.2 mr trend 6.9 % error mr 11-12 3.3 act ed -3.2 mr 08-12 -0.3 ct -4.3 mr trend 6.8 % error mr 11-12 -7.1 act ed 0.9 mr 08-12 -23.4 ct -13.7 mr trend 0.6 38 raymer j, biddle n and guan q australian population studies 1 (1) 2017 5.2 school projections for north canberra the multiregional projection method is particularly useful for capturing students transitioning between primary and high schools and between high schools and secondary colleges. this is further illustrated with schools in north canberra, an area with a relatively stable total population in terms of age composition and growth. table 6: observed and projected enrolments for schools in north canberra, 2013–2016 2013 2014 2015 2016 school obs ed mr obs ed mr obs ed mr obs ed mr a. observed and projected enrolments a 424 436 442 410 432 434 405 443 420 396 480 412 b 315 344 331 327 335 343 350 345 345 350 336 338 c 421 429 426 432 423 432 471 456 446 480 471 439 d 567 632 591 585 662 604 598 675 614 600 656 621 e 483 425 443 554 436 447 556 456 466 611 462 466 f 77 84 79 76 84 78 70 85 74 77 84 72 g 545 587 541 553 588 544 562 600 532 573 622 515 h 718 744 711 741 797 721 723 823 719 721 842 710 i 1,068 1,064 1,059 1,054 1,064 1,082 1,050 1,064 1,073 1,065 1,064 1,084 j 848 854 809 866 841 805 919 837 824 871 833 835 total 5,466 5,599 5,433 5,598 5,662 5,490 5,704 5,784 5,510 5,744 5,850 5,491 b. difference between projected and observed a 12 18 22 24 38 15 84 16 b 29 16 8 16 -5 -5 -14 -12 c 8 5 -9 0 -15 -25 -9 -41 d 65 24 77 19 77 16 56 21 e -58 -40 -118 -107 -100 -90 -149 -145 f 7 2 8 2 15 4 7 -5 g 42 -4 35 -9 38 -30 49 -58 h 26 -7 56 -20 100 -4 121 -11 i -4 -9 10 28 14 23 -1 19 j 6 -39 -25 -61 -82 -95 -38 -36 total 133 -33 64 -108 80 -194 106 -253 notes: obs = observed values; ed = act education directorate projection; mr = multiregional projection. the school level projections for north canberra focus on the level and between-school movements across seven primary schools (schools a–g), two high schools (schools h–i) and one secondary college (school j). in this illustration, only schools in north canberra are included, but the model framework could be extended to include any set of schools. also, for illustration purposes, we apply the average 2008–2012 transitions as the basis for estimating transitions for 2013–2016. australian population studies 1 (1) 2017 raymer j, biddle n and guan q 39 the projection results for schools in north canberra are presented in table 6 (panel a). also included are the corresponding observed values and the projections made by the act education directorate (panel b) with the closest value to the observed value shown in grey. the multiregional projection model out-performed the act education directorate’s projections for seven out of the 10 schools in each of the four projection years. these differences, however, are fairly modest. the real benefits of the multiregional model are that: (i) less assumptions are required; and (ii) there is a capacity to disaggregate the projection error. 6. discussion and conclusion understanding the demographic drivers of enrolment change is essential for making accurate and informed projections. variables influencing change include the birth of children in school intake areas, movements between government schools in a city or district, migration into or out of a city or region, and movements to or from non-government schools. the multiregional cohort projection model presented in this paper provides a flexible platform for including the main transitions affecting school enrolment change. by grouping schools in a multiregional model, understanding about student movements is increased and projection bias reduced. in order to make and assess projections, some understanding of the components of enrolment change and their trends is required. there is no single projection model that performs best in all situations. school districts should consider a variety of assumptions when developing projection models and adapt them to meet local differences. they need also to incorporate proposed or new housing developments and land releases which may result in increased migration by young families into the area and rapid population growth impacting education provision for the areas affected. as projections are often heavily scrutinised, the ability to explain trends in terms of the sources of growth provides a stronger evidence base and argument for school infrastructure, personnel and resource requirements. it also allows the projections producer to understand where the sources of error occurred in relation to changing enrolments over time. this is the main motivation underlying the multiregional cohort projections. we have demonstrated the variability in the sources of student enrolment change across the act and the relative stability in the different sources of enrolment change and cohort transitions. movements within and outside the act government school system can have large effects and are more difficult to predict. the multiregional school enrolment projection model captures these movements and may be applied to a wide array of situations. however, the transition data must be available. key messages • accurate projections of school enrolments and understanding of sources of error are essential for good school planning. • the multiregional projection model used in our study performed as well or better than a cohort transition model and current projection model used by the act education directorate. • a multiregional model that interrogates enrolment change can be used for shortto mediumterm enrolment projections in the act. 40 raymer j, biddle n and guan q australian population studies 1 (1) 2017 acknowledgements this paper is drawn from a previously commissioned review of school enrolment projection methodology prepared for the act education directorate. the authors would like to thank the directorate for their comments and suggestions, and xujing bai for her research assistance. references act government (2017) estimated resident population – september quarter 2016, viewed 19 december 2016, http://apps.treasury.act.gov.au/__data/assets/pdf_file/0008/644813/erp.pdf/_recache. berk & associates (2008) office of superintendent of public instruction k–12 school enrollment projections study: final report, viewed 19 december 2016, www.k12.wa.us/schfacilities/publications/pubdoc s/enrollprojectionmethodologiesfinalreport2008.pdf. gould e (1993) an interactive flow model for projecting school enrolments. international review of education 39(4): 319–332. grip r s (2009) does projecting enrollments by race produce more accurate results in new jersey school districts? population research and policy review 28(6): 747–771. herrick j h (1952) estimating future school enrollments in rapidly growing communities. educational research bulletin 31(4): 92–94. johnstone j n (1974) mathematical models developed for use in educational planning: a review. review of educational research 44(2): 177–201. johnstone j n and philp h (1973) the application of a markov chain in educational planning. socioeconomic planning science 7(3): 283–294. land k c and rogers a (eds) (1982) multidimensional mathematical demography: proceedings of the conference on multidimensional 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educational research association. washington dc, 20–24 april 1987, viewed 19 december 2016, http://files.eric.ed.gov/fulltext/ed283879.pdf. schoen r (1988) modeling multigroup populations. new york: plenum press. stone r (1965) a model of the educational system. minerva 3(2): 172–186. stronge w b and schultz r r (1981) models for projecting school enrollment. educational evaluation and policy analysis 3(5): 75–81. swanson d a and tayman j (2012) subnational population estimates. dordrecht: springer. sweeney s h and middleton e j (2005) multiregional cohort enrolment projections: matching methods to enrolment policies. population, space and place 11(5): 361–380. webster w j (1970) the cohort-survival ratio method in the projection of school attendance. the journal of experimental education 39(1): 89–96. webster w j (1971) an empirical comparison of selected enrollment projection formulas. the journal of educational research 64(8): 375–381. http://apps.treasury.act.gov.au/__data/assets/pdf_file/0008/644813/erp.pdf/_recache http://www.k12.wa.us/schfacilities/publications/pubdocs/enrollprojectionmethodologiesfinalreport2008.pdf http://www.k12.wa.us/schfacilities/publications/pubdocs/enrollprojectionmethodologiesfinalreport2008.pdf http://files.eric.ed.gov/fulltext/ed283879.pdf australian population studies 2018 | volume 2 | issue 1 | pages 14–25 © charles-edwards and panczak 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org elsewhere in australia: a snapshot of temporary mobility on the night of the 2016 census elin charles-edwards* the university of queensland radoslaw panczak the university of queensland * corresponding author. email: e.charles-edwards@uq.edu.au. address: queensland centre for population research, school of earth and environmental sciences, the university of queensland, brisbane, australia 4072 paper received 13 march 2018; accepted 2 may 2018; published 28 may 2018 abstract background temporary population mobility, moves of more than one night’s duration that do not entail a change in usual residence, are an important feature of the australian population surface. the abs census of population and housing (census) provides a snapshot of temporary movements one night every five years. aims this paper examines the intensity, age and spatial patterns of temporary movements captured at the 2016 census, and creates a classification of regions based on the age profile of movers on census nights. data and methods 2016 census data were extracted using abs tablebuilder pro. summary metrics were calculated to measure the intensity and age profile of movements. origin–destination flows were derived from a cross-classification of data on place of usual residence and place of enumeration. a classification of regions (sa4s) was constructed from the age profile of movers at origins and at destinations. results 1,142,005 individuals (about 5 per cent of the australian population) were enumerated away from home on census night 2016. mobility peaked in younger (20–30) and older (65–70) age groups. most movements were between capital city regions; however, resource regions and coastal areas were also implicated. the mobility surface was segmented by age: younger people dominated visits to cities and older movers comprise the majority of visitors to coastal areas, while remote areas had a significant proportion of visitors in the peak working ages. conclusions temporary population mobility is selective by age and sex and geographically segmented by these characteristics. improved understanding of the attribute of visitors to regions can assist to formulate and validate estimates of temporary populations from emerging data sets. key words temporary population mobility; non-residents; spatiotemporal populations; service populations; migration; census; australia. http://www.australianpopulationstudies.org/ mailto:e.charles-edwards@uq.edu.au australian population studies 2 (1) 2018 charles-edwards e and panczak r 15 1. introduction temporary population mobility drives significant short-term changes in national population distributions. population scholars, particularly in the developed world, have tended to ignore these movements in favour of permanent migration. this is changing. there is widespread recognition of the implications of short-term changes in population numbers for service provision (charles-edwards and bell 2013), emergency response and preparedness (canterford 2011; wilson et al. 2016) and disease transmission (bharti et al. 2011). data sets derived from social media (tenkanen et al. 2017), mobile telephones (silm and ahas 2010; deville et al. 2014) and other sources are providing new opportunities to monitor dynamics shifts in population numbers but are not a panacea. they are often partial, suffer from bias and lack detail on the underlying population flows and the characteristics of movers. it is against this backdrop that censuses and surveys have continued value for understanding temporary populations. this short paper explores the intensity and spatial pattern of temporary population mobility, along with the age and sex of movers, as captured by the australian bureau of statistics (abs) 2016 census of population and housing (census). it provides a short discussion of past studies of temporary population mobility in australia in section 2, then in section 3 briefly describes how temporary mobility is captured by the census and the limitation inherent in these data. section 4 reports the intensity of movements and age profile of movers as captured in 2016, and compares this to data collected at the 1996 census. in section 5, the spatial patterns of temporary flows are examined. in section 6, the sex and age characteristics of movers at origins and destinations are explored. brief conclusions are presented in section 7. 2. background temporary population mobility can be defined as moves more than one night in duration that do not entail a change in usual residence (bell and ward 2000). this separates temporary mobility from diurnal movements, such as daily commuting, and from permanent migration. there are some problems with this definition. many individuals do not have a single place of usual residence, for example, fly-in flyout (fifo)/drive-in drive-out (dido) miners and children in joint custody arrangements. the distinction between temporary and permanent mobility may also be unclear, with some ‘temporary’ movements stretching over years. notwithstanding, this definition has the advantage of being operationalised using common census definitions for place of usual residence and place of enumeration. temporary population movements are undertaken for a range of reasons. a simple distinction is between moves undertaken for work or production-related reasons (e.g. fifo/dido mining, seasonal agricultural labour and business travel) and moves undertaken for consumption-related reasons (e.g. tourism, second home travel, visits to friends and relatives). different types of mobility have distinct spatiotemporal signatures, with diverse destinations, durations, seasonal patterns and periodicities. for example, fifo mobility is spatially concentrated in resource regions and follows a common roster, such as two weeks on site followed by one week at home (mckenzie 2011). by contrast, coastal tourism can range from a few days to a few weeks in duration, is highly seasonal and concentrated in the summer months (charles-edwards and bell 2015). in addition to having distinct spatiotemporal signatures, temporary movers can be segmented according to age. in a schema proposed by mchugh, hogan and happel (1995), mobility in childhood and adolescence is tied to the family and may include both touristic mobility and mobility associated 16 charles-edwards e and panczak r australian population studies 2 (1) 2018 with family dissolution. in adulthood, mobility becomes increasingly tied to work, which can necessitate strategies such as long-distance commuting. with the transition to middle age, more financial resources enable some individuals to purchase second homes, initiating another form of temporary mobility. older age may be associated with a relaxation of work-related constraints on mobility, providing opportunities for new forms of recreational mobility and extended stays with children and grandchildren, but also additional constraints due to ill health. there have been a number of studies of temporary population mobility in australia drawing on census data (bell and brown 2006), data from the national visitor survey (charles-edwards, bell and brown 2008) and purposive surveys (mings 1997; hanson and bell 2007). bell and ward (1998) undertook the first systematic study of temporary population mobility in australia, utilising data from the 1991 census. they found that the incidence of temporary mobility remained relatively stable between the 1976 and 1991 censuses, with around 5 per cent of australians enumerated away from home on census night. the study found that temporary moves tended to cover longer distances than permanent moves, and revealed a regional pattern of net gains with inner cities, tourist regions and resource regions all attracting temporary visitors. follow up studies comparing temporary and permanent migration (bell and ward 2000) and the characteristics of temporary movers (bell and brown 2006) revealed the age profile of temporary movers, with movements selective of both younger (20–30 years) and older (65–70 years) adults. charles-edwards, bell and brown (2008) and charles-edwards and bell (2015), using data from the national visitor survey, confirmed the regionalisation of temporary movements but also the significant seasonal variation in spatial patterns tied to institutional and climatic factors. the current study provides an updated account of temporary population mobility in australia drawing on data from the 2016 census. it seeks also to extend our understanding of temporary moves by examining patterns of origin–destination flows and regional variations in the sex ratio and age profile of movers. the latter is of particular relevance to agencies interested in providing services to temporary populations. data on the age and sex of movers are also critical for the validation of emerging sources of data on temporary mobility. 3. data and methods data were sourced from the 2016 census. the census was conducted on a de facto residence basis, meaning that people were enumerated where they happened to be on census night, 9 august 2016. by combining data on place of usual residence and place of enumeration it is possible to generate a snapshot of people away from home (referred to as ‘visitors’ through the text) on one night every five years. the count of the number of people in australia enumerated away from their place of usual residence is coded in the usual address indicator (uaicp). uaicp data were extracted from the abs counting persons, place of usual residence census database within tablebuilder pro by age and sex to estimate the intensity of temporary population mobility on census night, along with the age profile of movers. while uaicp provides an estimate of the stock of people enumerated away from home on census night, it does not provide information on origin–destination flows. to explore the spatial distribution of movements, origin–destination matrices were constructed based on individuals’ place of usual residence (i.e. pur, the origin) and place of enumeration (i.e. poe, the destination) for statistical australian population studies 2 (1) 2018 charles-edwards e and panczak r 17 areas level 4 (sa4s). in tablebuilder pro, pur data and poe data are only available for crosstabulation in the counting employed persons, place of work database, which is restricted to individuals aged 15 years and older. all analyses were done in r (version 3.4.3, r core team 2018) with the circlize package used to draw the flow diagram (gu et al. 2014). maps were prepared using quantumgis software (qgis development team 2018). 4. how much movement? of 23,401,891 people enumerated on census night 2016, 1,142,005 (4.9%) were captured away from their usual residence. in relative terms, this figure has been remarkably stable over the past two decades, with 4.7 per cent of the population away from home at the 1996 census (bell and ward 2000). when we limit this to adults (aged 15 and over), 5.5 per cent of the population were away from home. while most moves were over short distances, almost a third of moves were between different states and territories. in addition to the 4.7 per cent of australians away from home on census night, the census enumerated 315,530 overseas visitors, equivalent to 1.3 per cent of the 2016 census count. like permanent migration, temporary mobility is highly selective by age and sex. the age schedule of temporary mobility is bimodal (figure 1). the highest levels of mobility are among older adults (65– 70 years) and younger adults (20–30 years). the peak in mobility at both older and younger ages reflects fewer work and family related constraints on these populations on a school night in midwinter. the lowest level of mobility is observed among school-aged children, with only 2 per cent enumerated away from home on census night. there are marked sex differentials in the mobility age schedules. mobility among young women peaks at a younger age and at a lower level than for men. it then drops to well below the male propensities during key labour force ages before it rises again to match male levels in retirement. figure 1: per cent of individuals away from home on census night by age and sex, 1996 and 2016 censuses source: abs 1996 and 2016 censuses. 18 charles-edwards e and panczak r australian population studies 2 (1) 2018 how might we explain these differences? the early peak in mobility among females is likely tied to age differentials in partnering and the absences associated with non-residential relationships. in key labour force ages, the lower mobility of women might reflect occupational structure, with women less likely to be employed in roles and industries associated with large amounts of travel (bell and brown 2006). women are also more likely than men to be constrained by childcaring roles limiting work-related mobility (abs 2016). sex differentials in movement at older ages may again reflect age differentials in partnering, with a persistent three to four year lag in mobility rates. there has been an ageing in the profile of movers since the 1996 census. mobility has decreased among younger men, with the percentage away at age 20 declining by more than 25 per cent. this decline has been offset by a substantial increase in the rate of movement across key labour force ages (25–65). for women, there has also been a drop in mobility in early adulthood. this is accompanied by a slight increase in rates between ages 25–45, but also a decline between ages 45–65. mobility in the retirement ages (65 and over) remained largely unchanged between 1996–2016, while movement intensity in infanthood dropped for both males and females. based on the schema set out by mchugh, hogan and happel (1995), these changes suggest a shift away from consumption-related moves, particularly at younger ages, towards production-related motivations for temporary movements on census night. 5. where do people move? figure 2: circular plot showing origin–destination flows between greater capital city statistical areas and sa4s (for the rest of australia), 2016 census australian population studies 2 (1) 2018 charles-edwards e and panczak r 19 figure 2 (above) shows the temporary flows recorded on census night between greater capital city statistical areas (gccsa) and sa4s (for the rest of australia). the circular plot represents all inter-sa4 flows, but only shows chords for flows greater or equal to 1,000 people. colour hues are used to define australian states and territories. the direction of the flow is defined by the colour of the origin and the presence of an arrow at the end of the chord. the width represents the number of movers. from figure 2 we learn a number of things. at the national level, we see that the most populous states of new south wales, victoria and queensland dominate the mobility system in terms of gross flows (i.e. both ins and outs). the largest flows originate and terminate in metropolitan areas, with the largest reciprocal flows between greater sydney and greater melbourne. greater brisbane is an important source of flows to greater sydney and greater melbourne, but is less attractive as a destination. another striking feature is the containment of larger flows within the states and territories, particularly in the resource states of western australia and queensland. of all states and territories, flows from victoria are the most widely dispersed across australia, with movers from victoria recorded in coastal tourism areas including the gold coast, sunshine coast and cairns (all in queensland). figure 3 shows the pattern of net mobility rate (nmr), which captures gains and losses for sa4s. nmr was calculated by subtracting the number of residents temporarily absent (i.e. out-movers) from the number of visitors (i.e. in-movers) divided by the usual resident population for each sa4. the pattern follows a north–south gradient with the greatest gains in northern australia, including outback areas of western australia, queensland and the northern territory, and the largest losses in the southern states. modest gains were also recorded in coastal destinations in southeast queensland and northern new south wales, as well as sa4s encompassing the alpine resort areas of new south wales and victoria. this is consistent with climatic factors dictating the timing and destination of some forms of temporary mobility (see charles-edwards and bell 2015). figure 3: net mobility rate (%) across sa4s, 2016 census note: number in brackets indicates number of regions in category. 20 charles-edwards e and panczak r australian population studies 2 (1) 2018 there is also a functional dimension to the mosaic of gains and losses. capital cities experienced net population losses except in their urban core, which experienced modest (e.g. greater brisbane) to large (e.g. greater sydney) gains. these gains are probably tied to business flows. gains in northwest western australia and central and southwest queensland are likely underpinned by mining and oil and gas extraction-related (fifo) mobility. 6. who moves where? the characteristics of movers are of interest to agencies involved in the planning and provision of services, as well as to researchers needing denominators for a range of social statistics. age and sex are the most critical attributes to be captured. figure 4 shows the sex ratio of visitors to sa4s across australia. the mobility surface is strongly differentiated by sex. males dominate temporary moves to resource regions including northwest western australia and central and southern queensland. the sex ratio is particularly skewed in northwest western australia with more than two male visitors for every female. sex ratios are also skewed in favour of males in the closely settled irrigated agricultural zone of southern new south wales and victoria. females dominate visitation to the suburbs and periphery of most urban areas (except greater perth), but not the central business districts. the sex ratio imbalance is in favour of females in southeast coastal districts of queensland. figure 4: sex ratio of visitors to sa4s, 2016 census note: the number in brackets indicates the number of regions in each category. we know that propensity to move varies across the life course. how does this manifest across space? to explore variations in the age structure of movers in both sending and receiving regions we grouped sa4s according to the age profiles of individuals temporarily absent from home (represented as an out-movement rate) and by the age profile of visitors to sa4s (measured as a proportion of all australian population studies 2 (1) 2018 charles-edwards e and panczak r 21 visitors to that sa4). clusters were selected using a k-means clustering algorithm implemented in the r package stats that determines the optimum partitioning of the dataset for a specified number of clusters. we derived four groups for residents away from home and four groups for visitors to sa4s. figure 5 shows the average age profile of absent residents for each of the four clusters and their spatial distribution. there are clear differences in both the level and age profile of mobility across sending regions. cluster 1 contains the most sa4s (n=28) and comprises the coastal regions of queensland and new south wales, as well as sa4s in greater adelaide, greater perth, greater darwin and other territories (not shown). outflows from this cluster are of average intensity and follow a bimodal pattern similar to the national distribution. sparsely populated outback areas comprise the majority of sa4s in cluster 2 (n=20). the out-movement rates are the highest (on average) for younger and middle-aged individuals, and the second highest for individuals aged 65 and over. figure 5: classification of sa4s based on age of absent residents, 2016 census note: the number in brackets indicates the number of regions in each category. we can surmise that the high level of mobility in part reflects trips to access goods and services located at considerable distances from home. sa4s in cluster 3 (n=16) have (on average) the highest 22 charles-edwards e and panczak r australian population studies 2 (1) 2018 proportion of individuals aged 65 and over away from home, and second largest proportion of people aged 20–29 away from home. sa4s belonging to this cluster are concentrated in the southeast corner of australia, which suggests a climatic motivation for absences on census night. cluster 4 is the second largest (n=24) and is characterised by low mobility at all ages. these sa4s are concentrated in greater sydney, greater melbourne and greater brisbane. the age profiles of movers are more varied at destinations than at origins. four clusters are shown in figure 6. note that the clusters are based on the proportion of visitors by age, and thus do not reflect the level of visitation. the biggest between-cluster differences are at younger ages (below age 35) and older ages (above age 60). sa4s in cluster 1 (n=35) and cluster 2 (n=27) have younger than average visitors. visitors to sa4s in cluster 3 and cluster 4 are older on average. figure 6: classification of sa4s based on age of visitors, 2016 census note: number in brackets indicates the number of regions in each cluster. cluster 1 is comprised of sa4s located in state and territory capital cities. visitors to these areas are more likely to be younger or in key labour force ages, suggesting employment as a key driver. cluster 2 has a similar age profile, but has a higher peak at younger ages and a lower proportion of visitors in australian population studies 2 (1) 2018 charles-edwards e and panczak r 23 key labour force ages. sa4s in this cluster are located on the peri-urban fringe of capital cities as well as southern coastal districts. the cluster includes the southern alpine ski resorts. cluster 3 (n=18) has a relatively high proportion of older visitors as well as visitors in key labour force ages. sa4s in this cluster include the mining resource regions of western australia and queensland, as well as large swathes of northern australia which are climatically most attractive during the winter months. this suggests that a combination of production and consumption motivations are driving visits to these regions. visitors to regions in the smallest cluster, cluster 4 (n=9), are older than average with relatively few individuals below age 50. sa4s belonging to this cluster are located in the coastal areas of northern new south wales and southeast queensland, and in northern queensland. 7. discussion and conclusion understanding the way in which populations shift over the course of a day, week and month due to temporary movements is important for planning and service provision, but also for the estimation of better dominators for a range of health and social statistics. this paper explored the intensity, age profile and patterns of temporary movements captured at the 2016 census. it also generated a classification of regions based on the age profile of residents absent on census night, and a separate classification of the age profile of visitors to australian regions. the results reveal that the intensity of temporary mobility in australia has remained stable over the past two decades, with a rate of around one in twenty. there have, however, been shifts in the age/sex profile, with movement increasingly dominated by males in key labour force ages. the impact of temporary population mobility on census night varies across australia. origin–destination flows connect metropolitan regions, particularly on the eastern seaboard. they distribute people from capital cities to regions in the resource rich states, and move victorians to high amenity parts of queensland. with respect to impact, the suburbs of major cities and regions in southern australia experience net losses. gains occur in remote and northern australia, selected high-amenity coastal districts and the core of major metro regions. when age is taken into account, a more differentiated mobility surface is revealed. at sending regions there is a close association between accessibility and the level of outmovement: the more remote an area, the higher the rate of out-movement. at destinations, there is a bifurcation between regions dominated by younger visitors and those more attractive to older australians. the former includes the capital cities and regions in the southeast corner of australia, while the latter incorporates the resource regions of central and northern australia and selected high-amenity coastal districts. census data provides a partial insight into temporary movements in australia, one night every five years. it provides no measure of seasonality, duration, frequency or periodicity, nor the complex circuits and motivations that underpin temporary moves. the spatial patterns observed will not be replicated at other times of the year: for example, during the january holiday period. the utility of census data for the estimation of temporary populations is therefore limited. it does, however, have the singular advantage of complete enumeration of temporary populations coupled with detailed information on the characteristics of movers. the emergence of new data sets, including those collected via social media and communication technologies, presents further opportunities for the generation of temporary population estimates. 24 charles-edwards e and panczak r australian population studies 2 (1) 2018 however, these data are often partial, biased and confounded by individual behaviour and may not reliably represent the population present. baseline data that accurately capture temporary populations and their characteristics, even if just for a single night, are essential for the production of robust estimates of non-resident populations. the integration of census data with emerging data sets forms a key aspect of an ongoing program of work (the tempo project: techniques for estimating mobile populations) aimed at developing techniques for estimating temporary populations in australia. key messages • one in twenty australians were enumerated away from their place of usual residence on census night 2016. this rate has been stable since 1996; however, the age and sex of movers has changed with males in key labour force age groups now much more likely to make temporary moves. • on census night temporary flows connect the capital cities in eastern australia; cities to resource regions in western australia and queensland; and victoria to high amenity parts of queensland and northern and outback australia. • inner cities and select coastal areas gain temporary movers, while the suburbs and southern regions lose residents. this is a winter pattern: the pattern of gains and losses is expected to look different in summer months. • the age of visitors varies across regions. understanding these patterns is important for local service provision, housing and planning. • the complete enumeration of temporary mobility by the census, even for a single night, provides an opportunity to validate estimates of temporary populations derived from new data sources, such as social media and mobile phone data. acknowledgements this research was supported through funding from 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https://dx.doi.org/10.1371%2fcurrents.dis.d073fbece328e4c39087bc086d694b5c australian population studies 2017 | volume 1 | issue 1 | pages 3–12 © mcdonald 2017. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org international migration and employment growth in australia, 2011–2016 peter mcdonald* the university of melbourne *corresponding author. email: mcdonald.p@unimelb.edu.au. address: melbourne school of population and global health, university of melbourne, vic 3010, australia paper received 26 july 2017; accepted 17 september 2017; published 20 november 2017 abstract background immigration to australia pre 1995 was largely low skilled. recessions led to competition between low-skilled domestic workers and new immigrants and subsequent cuts in migration intakes. historical changes in birth rates, increased participation in tertiary education, increasing numbers retiring and the relatively rapid restructuring of the skill level of labour demand combined to produce a skilled labour supply crisis in australia from the mid-1990s. the permanent and temporary skilled migration policies established by the australian government from 1995 played an important role in meeting that labour demand, especially in the boom years of the first decade of the 21st century. aims this paper examines the impact of immigration on employment in australia subsequent to the global financial crisis (gfc) for the five-year period from july 2011 to july 2016. data and methods data for the paper are sourced from the australian bureau of statistics. the paper uses survival methods to decompose the growth in employment in australia in the five-year period from 2011 to 2016: (1) change in age and sex distribution in the absence of migration; (2) changes in employment participation rates by age and sex; (3) net migration by age and sex. results immigration in response to strong labour demand has continued post gfc. from july 2011 to july 2016, employment in australia increased by 738,800. immigrants accounted for 613,400 of the total increase, population growth 98,900 and changes in employment participation only 26,500. migration has had a very large effect on the age structure of employment with most new immigrant workers (595,300) being under 55 years. conclusions research indicates that immigration provides major benefits to the australian economy. however, as strong labour demand is likely to sustain migration at relatively high levels in coming years, it is incumbent upon governments to plan for the effects of rapid population growth on infrastructure and resources. key words australia; labour demand; skilled migration; components of employment growth; global financial crisis (gfc). http://www.australianpopulationstudies.org/ mailto:mcdonald.p@unimelb.edu.au 4 mcdonald p australian population studies 1 (1) 2017 1. introduction this paper makes use of data from the abs labour force surveys for july 2011 (abs 2011) and july 2016 (abs 2016a) to examine changes in employment by age and sex in australia. the aim is to decompose changes in total employment in australia in this five-year period into three components: 1. change in the age and sex distribution in the absence of migration. 2. changes in employment participation rates by age and sex. 3. net migration by age and sex for the period 2011–2016. the study concludes that the third component, net migration, was clearly the largest of these three components. as this is a relatively new phenomenon, it is important to provide the historical context that has led up to this outcome. the purpose of the analysis is to provide a demographic accounting of changes in employment in the five-year period. as such, the analysis focuses on the supply of employment rather than demand. other methodologies such as computable general equilibrium (cge) modelling would be required to examine the demand side. also, though near to impossible to quantify, it should be remembered that the needs of new immigrants for goods and services creates labour demand that, in the absence of the migrants, would not have been apparent. the results provided are not net of this effect. 2. background the post-war migration program created in the late 1940s in australia had two main objectives: to provide workers for the expansion of australian industry, especially the manufacturing and construction industries; to increase the size of the australian population under the imperative of ‘populate or perish’. little attention was given to the skill level or english competency of the immigrants upon arrival because the labour demand was primarily for workers with low skills. as the various migrant groups established themselves in australia, the emphasis of migration shifted to the entry of family members of the prior immigrants. these family members, like their sponsors, were primarily people with low skills. as a consequence of these migration settings, whenever there was a downturn in the australian economy and an increase in unemployment (1961–1962, 1974–1975, 1983–1984 and 1991–1993), the migration program was wound back (figure 1). this was appropriate as the migrants competed very directly with low-skilled australians for the available jobs. this competition was heightened by the continuing expansion of the domestic labour force, which resulted both from the entry into the labour force of the baby-boom generation and the relatively low skills of the domestic population. with australia’s baby boom continuing into the early 1970s and small numbers of older workers retiring from the labour force, this situation of strong natural growth of the domestic labour force continued into the 1980s. from the 1980s onwards economic restructuring, especially the winding back of the manufacturing industry, led to the rapid decline of low-skilled jobs and a commensurate high demand for jobs requiring tertiary education and training. participation in tertiary education began to expand rapidly. in 1995 only 15 per cent of 25–29 year-old australians had a university degree. this had jumped to 37 per cent by 2015 (norton 2016, p. 68). as increasingly higher proportions of young australians australian population studies 1 (1) 2017 mcdonald p 5 pursued tertiary education and training, correspondingly, the number of young people employed in full-time jobs fell rapidly. for example, the number of 15–19 year olds employed full time fell from 463,000 in july 1989 to 240,000 in july 1993 and has continued to fall since then (abs 2016a). figure 1: net overseas migration, australia, 1947–2016(1) notes: (1) from 1 july 2006 (vertical line), the definition of net overseas migration was changed by the abs. the new definition made it more likely that temporary residents such as international students and temporary skilled workers would be counted into the population and coincided with a surge in these types of immigrants immediately after the definitional change. while net overseas migration is somewhat higher under the new definition compared with the old (especially in 2008), the average in recent years of around 200,000 per annum provides a reasonable comparison with the years prior to the definitional change. at the same time, demographic change in australia was putting an end to the natural growth of the domestic labour force. this is indicated starkly by the numbers in table 1. while in 1996 the population aged 25–29 was only 71 per cent of the size of the population aged 15–19, by 2016 the population aged 25–29 was 123 per cent of the population aged 15–19. finally, as evident also from table 1, the ratio of the near retirement age population (60–64 years) was just 41 per cent of the population aged 15–19 in 1966 but 83 per cent in 2016. to bring this situation into even sharper focus, the number of full-time workers aged 15–19 in 1978 was three times the number of full-time workers aged 60–64. in contrast, in 2016 the number of full-time workers aged 15–19 was just 39 per cent of the number aged 60–64. table 1: relative size of age groups in australia, 1966 and 2016 age group relative size of age group (%) (15–19 = 100%) 1966 2016 15–19 100 100 20–24 81 115 25–29 71 123 60–64 41 83 source: abs (2014). the long-term demographic shift resulting from historical changes in the birth rate combined with rapid restructuring of the skill level of labour demand, a hiatus of new entrants into the labour force 0 50,000 100,000 150,000 200,000 250,000 300,000 350,000 1 9 4 7 1 9 5 1 1 9 5 5 1 9 5 9 1 9 6 3 1 9 6 7 1 9 7 1 1 9 7 5 1 9 7 9 1 9 8 3 1 9 8 7 1 9 9 1 1 9 9 5 1 9 9 9 2 0 0 3 2 0 0 7 2 0 1 1 2 0 1 5 a n n u al n e t o ve rs e as m ig ra ti o n 6 mcdonald p australian population studies 1 (1) 2017 (associated with increased participation in tertiary education) and increasing numbers retiring compounded to produce a skilled labour supply challenge in australia from the mid-1990s. this was exacerbated in the early 2000s by the onset of the mining boom and its associated spin-offs into other industries. somewhat presciently, the australian government in 1995 had shifted its permanent migration program away from family migration to points-tested skilled migration and introduced an uncapped temporary skilled worker visa (the 457 visa). these well-timed changes in policy meant that as labour demand expanded in the 2000s, skilled migration could be ramped up effectively to meet the demand. the demand in the early 2000s was so strong that the australian government extended the right to apply for permanent residence to temporary residents onshore through employer sponsorship. this two-step process where migrants entered australia on a temporary visa, established themselves through employment with an employer and then applied for permanent residence as an employersponsored applicant had become the dominant pathway to permanent residence by the second decade of the 21st century. the story of these developments is told by gregory (2014) and mcdonald (2015). both authors argue that the two-step process is very effective because of the guaranteed employment of the migrant as opposed to the potentially long job search that needs to be undertaken by an independent skilled applicant. there were also substantial increases in migrants via the ‘family stream’ and ‘working holiday maker’ visa subclasses and numbers of international students. the latter two groups also have relatively high levels of employment. finally, the high australian dollar and strong labour demand led also to very large numbers of new zealand citizens taking up employment in australia under the open labour market policy of the two countries which had been established in the early 1980s (abs 2010). when the economic recession hit at the end of 2008, for the first time in australian history the australian government did not cut the immigration program. breunig, deutscher and to (2017) claim that there is no evidence to suggest that this approach had negative impacts on the labour market outcomes of domestic australian workers. with this background, the purpose of this paper is to examine post-global financial crisis (gfc) employment outcomes in australia and the ways in which immigrants have contributed to those outcomes. 3. data and methods the input data for the study were: • estimated resident population (erp) of australia by five-year age group and sex for 30 june 2011 and 30 june 2016. the erp values used were those estimated prior to the results of the 2016 census. • number of employed persons by five-year age group and sex from the july 2011 and july 2016 labour force surveys published by the australian bureau of statistics (abs 2011, 2016a). • five-year age group and sex-specific employment to population ratios from the same surveys • five-year life table survival ratios by age and sex calculated from the australian life tables for 2013–2015 published by the australian bureau of statistics (abs 2016b). step 1 in the method was to project the resident australian population in 2016 by five-year age groups and sex in july 2011 forward to july 2016 using the life table survival ratios. at the oldest australian population studies 1 (1) 2017 mcdonald p 7 ages, the population aged 85 and over was survived to 90 and over. this produced the estimated age and sex distribution of the population in 2016 in the absence of migration. in step 2 the employment to population ratios from 2011 were applied to the projected 2016 population. at the oldest ages, the published data required the use of age group 65 and over for this purpose. this step calculates the number of people who would have been employed in australia in 2016 in the absence of migration and under the assumption that there was no change in the employment to population ratios between 2011 and 2016. this yields the first component: 1. changes in numbers employed due to population growth resulting from the existing 2011 age distribution and mortality in the five-year period (referred to in the paper as ‘population growth’). step 3 applied the 2016 employment to population ratios to the 2016 projected population in the absence of migration. this calculates the number of people who would have been employed in 2016 in the absence of migration but using the actual 2016 employment to population ratios. the difference between the results of step 3 and step 2 produces the second component: 2. changes in employment numbers due to the change in the employment to population ratios. step 4, the final stage, compared the actual numbers by age and sex employed in 2016 with the result from step 3. the difference between the two, the residual, shows the effect of adding in migration along with any errors (sampling error in the two surveys; errors in the erp used to blow-up the survey results; errors in the assumed levels of mortality). this provides an estimate of the third component: 3. the effect of net migration in the period 2011–2016 on the total number of people employed in 2016. in relation to the errors, the sampling errors in the labour force survey are small and any error deriving from the survival ratios would be negligible as most of the calculations relate to younger ages. error deriving from errors in the erp are potentially larger, but the changes made to the erp following the results of the 2016 census are small by historical standards (abs 2017). it should also be noted that the 2016 census-adjusted erp was larger than the pre-census estimate, implying that the residual (the third component) would have been larger than estimated here if the 2016 censusadjusted erp had been used to adjust the 2016 labour force survey results. in the end, it is impossible to gauge the combined effect of these potential sources of error but it can be confidently concluded that any error in component 3 would be small and would be in the direction of increasing this component. while error can also apply to the estimation of components 1 and 2, the net effect of the errors would have been very small in relation to these components. there are implicit assumptions in the method that the new migrants had the same age-sex-specific employment to population ratios in 2016 as the domestic population, and that the employment to population ratios of the non-migrant population would not have changed in the absence of migration. as the age and sex distributions of both the migrant and non-migrant populations are taken into account in the calculations, and as the new migrants in 2016 constituted only 5 per cent of total employment, the effects of any errors in these implicit assumptions will be marginal. 8 mcdonald p australian population studies 1 (1) 2017 4. results figure 2 shows the results for three age groups: 15–24; 25–54 (the prime working ages); and 55 and over. total employment is also shown. looking first at the five-year change in total employment (738,800), the largest change was in the prime working ages (431,300) followed by the older ages (286,000), with only a very small positive impact evident for ages 15–24 (21,500). to provide some perspective for these numbers, the total number of employed persons in australia in july 2011 was 10,890,700. this means that employment increased by 6.8 per cent in the five years to july 2016. 4.1 youth employment the small net change at ages 15–24 was the result of a large negative component (-137,900) due to population change and a smaller negative amount (-40,100) due to falls in employment to population ratios for this age group, offset by a large gain (199,500) due to the third component, international migration. in other words, without migration, numbers employed in the age group 15–24 would have fallen substantially. employed recent migrants aged 15–19 are primarily international students and working holiday makers employed very largely in part-time shift work in the hospitality and retail industries. the other group employed in this way in the same industries, even larger in number than the migrant group, is australian students. along with the netherlands, students in australia are much more likely to be employed than students in any other oecd country (quintini 2015). in industries with very distinct peaks and troughs in demand, in terms both of the time of day and time of year, the availability of a large group willing to work under these conditions is highly beneficial to employers. furthermore, australian and international students and working holiday makers are usually much more highly skilled than the jobs require, meaning that productivity is enhanced. figure 2: decomposition of the change in the total number of people employed in australia between june 2011 and june 2016, ages 15–24, 25–54 and 55 and over -200 -100 0 100 200 300 400 500 c h an ge in e m p lo ym e n t (t h o u sa n d s) 15-24 25-54 55+ net migration 2011-2016 change in employment participation rates total population growth – no migration australian population studies 1 (1) 2017 mcdonald p 9 given that youth unemployment in australia is a serious issue, the counterfactual question arises: had there been zero migration at these ages, would australian employers have opted to employ unemployed non-migrants aged 15–24 to a much greater extent, or would total employment have been lower? in addressing this counterfactual question, it needs to be remembered that unemployed domestic job-seekers receiving the newstart allowance effectively need to find longer-term, full-time work. otherwise, they are in and out of the centrelink office every time they take a new job or their hours change and, in this situation, there is a strong chance that they will lose benefits for some periods. given the structure of the labour market at these ages, such jobs are hard to find. as the skills requirements of the australian labour market have shifted upwards, skilled workers are rarely aged under 20, or even in their early twenties, and the opportunities for low-skilled, full-time work at these ages have fallen dramatically. thus, while recent temporary migrants at this age may be in competition for jobs with full-time australian students, their absence from the australian labour market generally would not open opportunities for young australians receiving newstart payments. young unemployed australians have a low-skills problem in a skilled labour market and the social security system makes it difficult for them to take part-time, short-term jobs. while there may be some instances of displacement, the broad story is that they are not pushed out of jobs by migrants. 4.2 prime working ages employment in the prime working ages (25–54 years) in the five-year period rose a little through population growth but declined by a small amount due to changes in employment participation. the small decline related to participation was the result of an increase for women of 31,700 fully offset by a fall for men of 40,100. consequently, almost all of the substantial net growth in employment at these ages was due to migration (395,800 out of a total of 431,300, or 92 per cent). total unemployment in this age group in 2016, excluding unemployed recent immigrants, was 321,000. thus the job growth that was achieved could not have been achieved without migration, even in the extremely unlikely situation that unemployment in the domestic population at these ages had fallen to zero. for long-term unemployed australians in this age group, the issue once more was primarily inadequate skills and not competition from migrants. this is not to say that there is no competition from migrants for jobs that might be filled by domestic workers. as the 2014 independent review of the integrity of the 457 visa subclass for the australian government noted, it is important that the list of occupations open to temporary skilled workers is continuously monitored (azarias et al. 2014). 4.3 older ages migration had very little impact on the relatively substantial growth in employment at ages 55 and above. here, the main source of growth (192,900) was population growth as the baby-boom and subsequent large generations replaced the earlier smaller generations. employment participation also increased at these ages adding 75,000 additional employed persons. virtually all of these (73,600) were older women. while employment participation rates rose sharply for men at older ages in the decade 2000–2010, there was little change after 2010. for older women, the continued increase in employment participation rates through to 2016 is largely the result of cohort changes. 10 mcdonald p australian population studies 1 (1) 2017 each successive cohort of women has increased its participation at younger ages and these higher rates at younger ages have flowed on to higher rates at older ages for each successive cohort. 4.4 the age of the labour force because migrants are young, migration dramatically changes the age structure of employment in australia (table 2). without migration, employment at ages under 55 years would have fallen by 143,000 in the five-year period. instead, with migration, employment at these ages increased by 452,000, a total turnaround of 595,000. at the same time, employment would have increased at older ages without migration by 268,000 and hardly increases when migration is included. in an age where young people are the assimilators of new technology, this impact of migration on the age structure of the labour force is likely to be highly beneficial to the economy. in addition, there is a growing argument that older and younger workers are complementary rather than substitutes for each other: younger workers have the technical skills, while older workers have the experience of how these skills might be utilised. table 2: change in numbers employed by broad age group with and without migration, 2011–2016 age group without migration with migration <55 years -143,000 452,000 55 years and over 268,000 286,000 there is also a gender effect of migration. without migration, male employment would have increased by just 6,000 in the five-year period in net terms. instead, including migration, it increased by 306,000. 5. discussion and conclusion the analysis here shows that immigration had a very large impact on employment change in australia between 2011 and 2016. while this is not an analysis of the economic benefits of migration to australia, a number of relatively recent studies provide some indication of these benefits. for example, in the context of a study which showed that immigration negatively affected the wages of low-skilled workers in most oecd countries, docquier, özden and peri (2010, p. 14) found that the ‘reverse takes place in canada and australia where immigration strongly helps the wages of less educated (+3.3 and +4.5% respectively)’. a report by mcdonald and temple (2013, p. 10) on the long-term effects of ageing and immigration on labour supply and per capita gross domestic product in australia concluded: ‘to draw a more definite conclusion, if the aim is to optimize gdp per capita growth through to [year] 2053, nom [net overseas migration] between about 160,000 and 220,000 seems to do this if it is assumed that the migrants’ have the same rate of labour productivity growth as the general australian population. a broad-based study published by migration council australia utilised the independent macroeconometric model to simulate migration scenarios and concluded: the economic impact of migration flows through into every aspect of the economy. it has a profound positive impact not just on population growth, but also on labour participation and employment, on wages and incomes, on our national skills base and on net productivity. (migration council australia 2015, p. 2) australian population studies 1 (1) 2017 mcdonald p 11 the productivity commission (2016, p. 2) similarly investigated the economic impacts of immigration, finding: ‘australia’s current immigration profile is projected to deliver a demographic dividend to australia and higher economic output per person.’ a further study for the productivity commission by breunig, deutscher and to (2017, p. 1) concluded: ‘we find almost no evidence that immigration harms the labour market outcomes of those born in australia’. referring to regional employment impacts, golebiowska, elnasri and withers (2016, p. 449) found: policy design—particularly the two-step visa process for regional migrants—has allowed substantial and effective regional location encouragement for immigrants over the past decade. … the job-creation dimensions of immigration may mean that regional policies seeking greater population growth … can be benefited by the use of targeted migration visa entry conditions. on the other side of the equation, there are negative externalities created by rapid population growth such as congestion and pressure on natural resources, urban infrastructure and housing. sobels et al. (2010) concluded: ‘the macro-scale modelling found that higher levels of nom [net overseas migration] impose greater adverse impacts on the quality of our natural and built environments, other things being equal’. it is clear that strong labour demand in australia in the first decade of the 21st century led to relatively high immigration and that this had significant economic benefits. this paper has shown that immigration in response to strong labour demand has continued following the gfc. in the next decade, very strong labour demand can be expected in the caring sector with the implementation of the national disability insurance scheme and natural growth also in aged care, and in the construction sector with increased emphasis on infrastructure development. meeting these demands will have spin-offs in other sectors. the work of golebiowska, elnasri and withers (2016) indicates that migration plays an important role also in regional development. while there may be surges in temporary migration from time to time (as in 2008), in the longer term the level of immigration is determined by the setting of the federal target for the permanent migration program. the australian government has set this target at 190,000 persons per annum for 2017–2018 and the next three years. this means that relatively high population growth will continue. recognising that there exist potential negative implications of rapid population growth, particularly for sydney and melbourne, it is incumbent upon governments to plan for the effects of this inevitable population growth on both infrastructure and resources. key messages • historical changes in the birth rate, the hiatus of new entrants into the labour force as young australians increased their participation in tertiary education, increasing numbers retiring and the relatively rapid restructuring of the skill level of labour demand all combined to produce a skilled labour supply challenge in australia from the mid-1990s. • skilled migration, both permanent and temporary, played an important role in meeting this labour demand. • immigration in response to strong labour demand continued after the gfc and had a highly significant impact on the growth of employment in australia between 2011 and 2016. • it is incumbent upon governments to plan for the effects that inevitable population growth will have on infrastructure and resources in the coming years. 12 mcdonald p australian population studies 1 (1) 2017 references australian bureau of statistics (abs) (2010) new zealanders in australia. in: australian social trends, abs cat. no. 4102.2. canberra: abs. australian bureau of statistics (abs) (2011) 6291.0.55.001 – labour force, australia, detailed – electronic delivery, jul 2011, viewed 1 july 2017, http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/e0b54015bb216045ca257 90b001620fd?opendocument. australian bureau of statistics (abs) (2014) 3105.0.65.001 – australian historical population statistics, 2014. population age-sex structure, data cube: excel spreadsheet, viewed 1 july 2017, http://www.abs.gov.au/ausstats/abs@.nsf/detailspage/3105.0.65.0012014?opendocument. australian bureau of statistics (abs) (2016a) 6291.0.55.001 – labour force, australia, detailed – electronic delivery, jul 2016, viewed 1 july 2017, http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/5a9245950663a4f6ca258 035007fee80?opendocument. australian bureau of statistics (abs) (2016b) 3302.0.55.001 – life tables, states, territories and australia, 2013–2015, viewed 1 july 2017, http://www.abs.gov.au/ausstats/abs@.nsf/detailspage/3302.0.55.0012013-2015?opendocument australian bureau of statistics (abs) (2017) australian demographic statistics, december quarter 2016, abs cat. no. 3101.0. canberra: abs. azarias j, lambert j, mcdonald p and malyon k (2014) robust new foundations: a streamlined, transparent and responsive system for the 457 programme, viewed 1 july 2017, http://www.border.gov.au/reportsandpublications/documents/reviews-andinquiries/streamlined-responsive-457-programme.pdf. breunig r, deutscher n and to h-t (2017) the relationship between immigration to australia and the labour market outcomes of australian-born workers. economic record 93(301): 255–276. docquier f, özden c and peri g (2010) the wage effects of immigration and emigration. nber working paper no. 16646. cambridge, massachusetts: national bureau of economic research. golebiowska k, elnasri a and withers g (2016) responding to negative public attitudes towards immigration through analysis and policy: regional and unemployment dimensions. australian geographer 47(4): 435–453. gregory r (2014) cameo 3. the two-step australian immigration policy and its impacts on immigrant employment outcomes. in: chiswick b and miller p (eds) handbook of the economics of international migration, vol. 1. north holland: elsevier; 1421–1443. mcdonald p (2015) international migration and employment in australia. population review 54(2): 1–12. mcdonald p and temple j (2013) the long term effects of ageing and immigration upon labour supply and per capita gross domestic product: australia 2012–2062, final report, viewed 1 july 2017, http://www.demographicinsight.com.au/other/mcdonaldtemple%20-%20web.pdf. migration council australia (2015) the economic impact of migration. canberra: migration council australia. norton a (2016) mapping australian higher education 2016, grattan institute report no. 2016–11. melbourne: grattan institute. productivity commission (2016) migrant intake into australia. productivity commission inquiry report no. 77, 13 april 2016. canberra: commonwealth of australia. quintini g (2015) a picture of working students in oecd countries, viewed 1 july 2017, https://oecdskillsandwork.wordpress.com/2015/09/02/a-picture-of-working-students-in-oecdcountries/. sobels j, richardson s, turner g, maude a, tan y, beer a and wei z (2010) long-term physical implications of net overseas migration: australia in 2050. adelaide sa: national institute for labour studies, flinders university. http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/e0b54015bb216045ca25790b001620fd?opendocument http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/e0b54015bb216045ca25790b001620fd?opendocument http://www.abs.gov.au/ausstats/abs@.nsf/detailspage/3105.0.65.0012014?opendocument http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/5a9245950663a4f6ca258035007fee80?opendocument http://www.abs.gov.au/ausstats/abs@.nsf/allprimarymainfeatures/5a9245950663a4f6ca258035007fee80?opendocument http://www.abs.gov.au/ausstats/abs@.nsf/detailspage/3302.0.55.0012013-2015?opendocument http://www.border.gov.au/reportsandpublications/documents/reviews-and-inquiries/streamlined-responsive-457-programme.pdf http://www.border.gov.au/reportsandpublications/documents/reviews-and-inquiries/streamlined-responsive-457-programme.pdf http://www.demographicinsight.com.au/other/mcdonaldtemple%20-%20web.pdf https://oecdskillsandwork.wordpress.com/2015/09/02/a-picture-of-working-students-in-oecd-countries/ https://oecdskillsandwork.wordpress.com/2015/09/02/a-picture-of-working-students-in-oecd-countries/ australian population studies 2020 | volume 4 | issue 1 | pages 1-3 © piggott 2020. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org introduction to the special issue on population ageing in australia john piggott* the university of new south wales * email: j.piggott@unsw.edu.au. address: arc centre of excellence in population ageing research, university of new south wales, level 3, 223 anzac parade, kensington, nsw 2033, australia. paper received 2 may 2020; accepted 4 may 2020; published 25 may 2020. it is a great privilege to have the opportunity to write an introduction to this important issue of this new and exciting journal. it is very heartening that the editors have chosen to devote an entire issue to the topic of population ageing. population ageing affects all of us and it impacts many dimensions of our lives. from changed family structures, workplace cultures, through to retirement support and health and aged care arrangements, households are facing unfamiliar, sometimes irreversible, complex and critical life choices. it is exerting unprecedented pressures on traditional social institutions, both in australia and around the world. sustained falls in fertility, sometimes to “super-low” levels, are combining with increasing life expectancy to drive global movements in labour, capital and trade in ways that are still unknown. employers will have to learn to deal with and accommodate an older workforce. and governments under fiscal stress are reducing their commitment to pensions, health and aged care, raising new private sector opportunities and challenges for regulation and governance. these adjustments will have flow-on effects to intergenerational exchange and equity and policy formulation. as the un has said, the phenomenon of population ageing is unprecedented, enduring, pervasive, and profound. research is critically required to better understand how policy and practice innovation can ease our individual and collective paths through this transition. longer life is one of humanity’s greatest achievements. it is important that this substantial contribution to human welfare is fully leveraged by moving to policy structures and private sector activity in the best possible way. this requires new knowledge and an evidence base informed by multiple disciplines. the need for cutting edge research related to demographic ageing is documented in the international literature. this is especially true when the focus is on increasing lifespan. in the 2016 application for renewed funding for the arc centre of excellence in population ageing research (cepar), we listed calls for a greater research effort in the world health organisation (2015) and the us national research council (2013), which emphasises the advantages of an inter-disciplinary approach to the issue. an especially useful benchmark is provided in national research council (2012). chapter 10 identifies the following major research needs: demographic and health measurement and projections; capacity to work longer and longer working life; changes in consumption and saving; and modelling efforts and data needs. about:blank about:blank 30 piggott australian population studies 4 (1) 2020 and there has been at least some response on the international stage. last year, the year that japan, the world’s oldest nation, hosted the g20 meetings, a task force was established under its auspices to examine population ageing (see, for example, chomik et al. 2019). the world health organisation is promoting the 2020s as the “decade of healthy aging”, leading up to the deadline for the sustainable development goals in 2030. and the us national academy of medicine has launched a commission on a “roadmap to health longevity”. but natural population increase is in some ways more important. australia remains a young country by developed country standards. partly, this is because social and family institutions are supportive of fertility. but if this were all we had, our population would still age quite rapidly and total population, and national income, would eventually decline. the total fertility rate sits well below replacement. critical to the slowing of population ageing is australia’s immigration policies, which are well targeted to keeping the population young. australia’s continuing economic prosperity depends on the maintenance of strong and well-targeted migration, and targeting depends on our international education industry. something like half of new permanent residents in australia have previously been students here. even though this is primarily a journal about australian population, it is important to recognise the impact on this nation of international demographic forces. china is currently younger than australia but is rapidly catching up – some estimates have china older than australia by the middle of this century. what does this mean for china-australia trade? for migration? for international education services? and china, while enormously important, just leads the pack of emerging economies in asia, all of them important to australia, where fertility has fallen sharply, and demographic transition is an established dynamic. it may well be that changes in international demography end up being more important influences on australia’s future than its own demographic change. in the meantime, there is no shortage of relevant and important research questions. for example: how will australia’s age structure change in the future? will covid-19 make any difference to it? how will the fertility differential shift, and what will the social implications of the shift be? how do households learn to adjust to changing demographic realities, and how does cognitive decline in older ages affect their abilities to make major life decisions? will product innovations help them in this challenge? how do organisations change their behaviour to facilitate greater participation by older workers? is retiring later good for you? does work lead to more, or less, successful ageing? and when you turn from understanding the micro-transition better, and ask broader social and economic questions, solid evidence is even harder to find. to list a few: how will an ageing demographic affect government budgets and services, and social and economic inequality, both between and within generations? how should the government best set policies to respond to demographic change? as retirement risks, and later life risks more generally, become more important, how will markets respond? will management of this kind of risk sit at all in the private sector, or will it remain for government to be the insurer? how can policy innovation help shape broader and better allocated age-related risk sharing and management between the public sector, business, and households? australian population studies 4 (1) 2020 piggott 29 there is at least some research on all these questions. but there are definitive answers to none of them. special issues such as these serve to focus research attention on these unanswered questions, and in so doing, render us all a considerable service. acknowledgements this research was supported by the australian research council centre of excellence in population ageing research (project number ce170100005). references chomik r, piggott j and yan s (2019) aging, fiscal sustainability, and adequacy of social security systems. in asian development bank institute (ed.) aging societies: policies and perspectives. tokyo: asian development bank institute; 52-64. national research council (2012) aging and the macroeconomy: long-term implications of an older population. washington, dc: the national academies press. national research council (2013) new directions in the sociology of aging. washington, dc: national academies press. world health organisation [who] (2015) world report on ageing and health. geneva: world health organisation. it is a great privilege to have the opportunity to write an introduction to this important issue of this new and exciting journal. it is very heartening that the editors have chosen to devote an entire issue to the topic of population ageing. population ageing affects all of us and it impacts many dimensions of our lives. from changed family structures, workplace cultures, through to retirement support and health and aged care arrangements, households are facing unfamiliar, sometimes irrev... research is critically required to better understand how policy and practice innovation can ease our individual and collective paths through this transition. longer life is one of humanity’s greatest achievements. it is important that this substantial... the need for cutting edge research related to demographic ageing is documented in the international literature. this is especially true when the focus is on increasing lifespan. in the 2016 application for renewed funding for the arc centre of excelle... and there has been at least some response on the international stage. last year, the year that japan, the world’s oldest nation, hosted the g20 meetings, a task force was established under its auspices to examine population ageing (see, for example, c... but natural population increase is in some ways more important. australia remains a young country by developed country standards. partly, this is because social and family institutions are supportive of fertility. but if this were all we had, our popu... critical to the slowing of population ageing is australia’s immigration policies, which are well targeted to keeping the population young. australia’s continuing economic prosperity depends on the maintenance of strong and well-targeted migration, and... even though this is primarily a journal about australian population, it is important to recognise the impact on this nation of international demographic forces. china is currently younger than australia but is rapidly catching up – some estimates have... in the meantime, there is no shortage of relevant and important research questions. for example: how will australia’s age structure change in the future? will covid-19 make any difference to it? how will the fertility differential shift, and what will... and when you turn from understanding the micro-transition better, and ask broader social and economic questions, solid evidence is even harder to find. to list a few: how will an ageing demographic affect government budgets and services, and social an... there is at least some research on all these questions. but there are definitive answers to none of them. special issues such as these serve to focus research attention on these unanswered questions, and in so doing, render us all a considerable service. acknowledgements references australian population studies 2019 | volume 3 | issue 2 | pages 29-33 © lock and pettit 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org visualising population distribution in australia over time using rapid 3d web graphics libraries oliver lock* university of new south wales chris pettit university of new south wales * corresponding author. email: o.lock@unsw.edu.au. address: city analytics lab, faculty of built environment. red centre west wing, university of new south wales. kensington, nsw 2033. australia. paper received 1 may 2019; accepted 29 may 2019; published 18 november 2019 this paper presents an interactive 3d visualisation tool and workflow for exploring current and past population data in australia. the visualisation of small-area population data enables the exploration of population dynamics, such as scale, density, movement, age and sociodemographic information. such information is becoming increasingly accessible with the advent of open government data (jetzek et al. 2013), sensor data (sagl et al. 2012), and more sophisticated computational and visualisation tools (kashnitsky and schöley 2018; o’brien and cheshire 2016; pettit et al. 2012; pettit et al. 2017). such tools enable planners, geographers, demographers to understand the current structure of cities and how they are changing over time. there are a number of challenges in representing small-area population geographies in a userfriendly way at a large national (or, indeed, international) scale. these geographies consist of statistical boundaries which can vary significantly in area. the rendering of density and colour breaks can further be difficult, and often can skew the visibility of interconnecting regional cities and centres. due to the complexity of boundary geometries, it can be computationally slow to show national datasets in standard gis applications, and even in web applications they are particularly difficult to interpret when zoomed out as a consequence of preserving the legibility of these boundaries. several systems have been developed to address the visualisation of detailed population data at a large scale by using methods which ameliorate effects of administrative population boundaries. for example, work by smith (2016) discusses this, and creates an interactive 2d population explorer using the open release of the european commission (2019) global human settlement layer. to overcome these challenges this demographic presents a novel approach (figure 1) using rapid, open source 3d web visualisation libraries to explore how this can be achieved with national-level population data in australia. d em og ra ph ic http://www.australianpopulationstudies.org/ mailto:o.lock@unsw.edu.au 30 lock & pettit australian population studies 3 (2) 2019 figure 1: australian population explorer note: access the interactive version via https://aus3dpop.city-informatics.com webgl operates across multiple supported browsers (chrome, firefox, safari) with a royalty-free api (application programming interface), and creates fast, hardware accelerated 3d graphics (khronos group 2019). the open-source webgl-based library deckgl (uber 2019) was used due to its specialisation in processing very large geographic data sets and rendering them in three dimensions. three dimensional techniques are a sensible choice for displaying population density, which has a natural perceptual association with its impact on the height and size of the built environment to support that density. the method used in this visualisation is known as ‘hexagon binning’. a hexagon bin is a form of bivariate histogram which considers both its location and a frequency of values underneath it. the process of generating a hexagon bin is as follows: • geographic space is transformed into a regular grid of hexagons; https://aus3dpop.city-informatics.com/ australian population studies 3 (2) 2019 lock & pettit 31 • the number of points (in this instance, population) falling into each hexagon is counted; • hexagons with a count above 0 are plotted, with their colour and height varying with the density of points underneath. there are several reasons why hexagons are useful (lewin-koh 2011). hexagons are more efficient than covering a plane with squares. they are also visually less biased for displaying densities than other regular tessellations with fewer edges (and thus an implied visual directionality). as such, they provide a sound medium for communicating population and related urban densities. for this visualisation, usual residence census data from the smallest geographic unit for population data within the abs census data was used, mesh blocks. according to the abs (2016), mesh blocks contain around 30-60 dwellings, the smallest number of dwellings that can be communicated without potentially revealing sensitive information. the amount and geometry of mesh blocks has changed over time, from the 2006 census (when originally conceived) when there were approximately 314,000 to approximately 347,000 in 2011 and 358,000 in 2016. a challenge lies in their evolving geometries as their visual comparison is unclear over time. another challenge, as discussed, is in computing the complex, detailed geometries and trying to represent such granular polygons at national scale. the resulting visualisation is available through australian population explorer (lock 2019). the tool is rapid and exploratory. users can toggle between alternate years of the census and see changes in population distribution. further, changes can be made in the coverage of the hexagon to explore more densely populated areas. the lower percentile toggle can be used to see which areas fall in the highest densities of all hexagons generated across the country. it can be seen that australia’s major cities continue to operate as primate cities within their respective states/territories, however, such visualisation also highlights the country’s vast network of regional cities and the interconnectedness of urban regions such as in south-east queensland. by increasing the radius of the hexagon to 10km, and around the 95th percentile, users can begin to see australia’s network of smaller cities and how they may connect to one another, which could, for example, be useful in considering future, major infrastructure projects. with a smaller hex bin it is clearly visible that 2006 and 2011 have greater similarity in population structure and pattern than in 2016. this is likely due to a combination of factors related to the new digital version of the census in 2016, including changes in response rates, imputation challenges and new address-matching systems (the address register), documented by census independent assurance panel (harding et al. 2017). this representation difference was mitigated by increasing the hexagon sizes. by changing size dynamically, it is easier to compare cities over time and highlight overarching structures – see for example components b, c and d of figure 1. in summary, the australian population explorer presented here permits the interactive investigation of population distribution and trends over time. this contributes to our understanding of effective methods to represent detailed small-area information, which can be useful across multiple domains. such applications include planning and delivering of government services, transportation planning, 32 lock & pettit australian population studies 3 (2) 2019 estimating vulnerable communities in disaster situations, understanding communities for election preparation, estimation of population at risk for spread of diseases (wardrop et al. 2018). references australian bureau of statistics [abs] (2018) population projections, australia, 2017 (base) – 2066. catalogue no. 3222. canberra: abs. australian bureau of statistics [abs] (2016) australian statistical geography standard (asgs): volume 1 main structure and greater capital city statistical areas, july 2016. catalogue no. 1270.0.55.001. canberra: abs harding s, jackson pulver l, mcdonald p, morrison p, trewin d and voss a (2017) report on the quality of 2016 census data. http://www.abs.gov.au/websitedbs/d3310114.nsf/home/independent+assurance+panel chen c, ma j, susilo y, liu y and wang m (2016) the promises of big data and small data for travel behavior (aka human mobility) analysis. transportation research part c: emerging technologies, 68, 285–299. https://doi.org/10.1016/j.trc.2016.04.005 european commission (2019) ghsl global human settlement layer. https://ghsl.jrc.ec.europa.eu/index.php. accessed on 28 march 2019. jetzek t, avital m and bjørn-andersen n (2013) generating value from open government data. proceedings of the 34th international conference on information systems 1-20. http://aisel.aisnet.org/cgi/viewcontent.cgi?article=1181&context=icis2013. kashnitsky i and schöley j (2018) regional population structures at a glance. the lancet 392(10143): 209– 210. https://doi.org/10.1016/s0140-6736(18)31194-2 khronos group (2019) webgl opengl es for the web. https://www.khronos.org/webgl/. accessed on 25 june 2019. lewin-koh n (2011) hexagon binning: an overview. http://cran.rproject.org/web/packages/hexbin/vignettes/hexagon_binning.pdf. accessed on 28 march 2019. lock o (2019) australian population explorer. https://aus3dpop.city-informatics.com/. accessed on 25 june 2019. o’brien o and cheshire j (2016) interactive mapping for large, open demographic data sets using familiar geographical features. journal of maps 12(4): 676–683. https://doi.org/10.1080/17445647.2015.1060183 pettit c j, tanton r and hunter j (2017) an online platform for conducting spatial-statistical analyses of national census data across australia. computers, environment and urban systems 63: 68–79. https://doi.org/10.1016/j.compenvurbsys.2016.05.008 pettit c, widjaja i, russo p, sinnott r, stimson r and tomko m (2012) visualisation support for exploring urban space and place. in: isprs annals of the photogrammetry, remote sensing and spatial information sciences 1: 153–158. https://doi.org/10.5194/isprsannals-i-2-153-2012 sagl g, resch b, hawelka b and beinat e (2012) from social sensor data to collective human behaviour patterns – analysing and visualising spatio-temporal dynamics in urban environments. gi_forum 2012: geovisualization, society and learning 1: 54–63. https://doi.org/10.1080/01441647.2019.1616849 smith d a (2016) online interactive thematic mapping: applications and techniques for socio-economic research. computers, environment and urban systems 57: 106-117. https://doi.org/10.1016/j.compenvurbsys.2016.01.002 uber (2019) deck.gl. https://deck.gl/. accessed on 24 january 2019. http://www.abs.gov.au/websitedbs/d3310114.nsf/home/independent+assurance+panel https://doi.org/10.1016/j.trc.2016.04.005 https://ghsl.jrc.ec.europa.eu/index.php http://aisel.aisnet.org/cgi/viewcontent.cgi?article=1181&context=icis2013 https://doi.org/10.1016/s0140-6736(18)31194-2 https://www.khronos.org/webgl/ http://cran.rproject.org/web/packages/hexbin/vignettes/hexagon_binning.pdf https://aus3dpop.city-informatics.com/ https://doi.org/10.1080/17445647.2015.1060183 https://doi.org/10.1016/j.compenvurbsys.2016.05.008 https://doi.org/10.5194/isprsannals-i-2-153-2012 https://doi.org/10.1080/01441647.2019.1616849 https://doi.org/10.1016/j.compenvurbsys.2016.01.002 https://deck.gl/ australian population studies 3 (2) 2019 lock & pettit 33 wardrop n a, jochem w c, bird t j, chamberlain h r, clarke d, kerr d, bengtsson l, juran s, seaman v and tatem a j (2018) spatially disaggregated population estimates in the absence of national population and housing census data. proceedings of the national academy of sciences 115(14): 3529–3537. https://doi.org/10.1073/pnas.1715305115 https://doi.org/10.1073/pnas.1715305115 australian population studies 2019 | volume 3 | issue 2 | pages 1-15 © gray and evans 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org changing education, changing fertility: a decomposition of completed fertility in australia edith gray* the australian national university ann evans the australian national university * email: edith.gray@anu.edu.au. address: school of demography, research school of social sciences, the australian national university, act 2601 paper received 23 may 2019; accepted 3 september 2019; published 18 november 2019 abstract background the expansion of education in australia, particularly for women, is one of the most significant social changes of the last five decades. the relationship between education and fertility has been widely studied, showing that increases in higher education for women are consistently associated with lower fertility. given the close link between education and fertility, this paper questions what effect the changing educational profile of australian women has had on overall fertility trends. aims this paper investigates the effect of the increase in education on completed fertility by decomposing the change in overall completed fertility into two components: (1) change in completed fertility as a result of the proportion of women in different education categories and, (2) changes in completed fertility of women in each education category. data and methods the study uses 2016 census data on the number of children ever born of five cohorts of women born between 1952 and 1976. decomposition is used to distinguish the effects of the two components. results the educational composition of women in these cohorts is dramatically different, with an increasing number of women having completed tertiary education in later cohorts. completed fertility has also changed across successive cohorts. we find that for the earliest cohorts most of the decline is due to declines in completed fertility within education categories, but for later cohorts the decline is attributable to increases in the proportion of women with higher levels of education. conclusions despite tertiary education becoming much more common, fertility within this group remains lower than other education groups. while other countries have seen a narrowing of the gap in fertility rates between education groups, this pattern is not found in australia. key words education; fertility; fertility decline; children ever born; census; decomposition. http://www.australianpopulationstudies.org/ mailto:edith.gray@anu.edu.au 2 gray & evans australian population studies 3 (2) 2019 1. introduction the expansion of education in australia is one of the most significant social changes of the last five decades. the 2016 census marked the first time in australian history that the proportion of women aged 40-44 with a university degree (36 per cent) exceeded the proportion with no post-school qualification (30 per cent). this is a remarkable increase from 30 years earlier when just 5 per cent had a university degree and 70 per cent had no post-school qualification (abs 1988). given the close link between education and fertility, we question what effect the changing educational profile of the population has had on overall fertility trends over time. as the category of women with higher educational qualifications has become less selective (adsera 2017), has the negative relationship between educational attainment and fertility weakened for younger cohorts? the relationship between education and fertility has been one of the most widely studied topics in demography. decades of research has consistently found that at both the individual and population level, higher education is almost universally associated with lower fertility (cochrane 1979; caldwell 1980; rindfuss et al. 1996; musick et al. 2009). women with higher levels of education tend to start childbearing later, have fewer children overall and are more likely to be childless. the reasons for this are numerous and include the ‘incarceration effect’ of longer time spent enrolled in education which delays the start of family formation (heck et al. 1997; ní bhrolcháin and beaujouan 2012), economic considerations including increased opportunity costs, changes in cultural or attitudinal factors such as increased knowledge and decision-making power regarding contraceptive use, and different values regarding gender and family dynamics (fort et al. 2016; neels et al. 2017). over time, the difference in fertility between those with high and low education, can develop in three ways. they can: (1) narrow, (2) widen, or (3) stay stable. recent research looking at change in educational differences across cohorts has been mixed. in south korea, yoo (2014) found that educational differences in completed fertility almost disappeared as the country went through the fertility transition. similarly, in denmark, norway and sweden education differences in cohort fertility have virtually disappeared in younger cohorts (jalovaara et al. 2018; andersson et al. 2009). however, a convergence of fertility across educational categories is not evident in all countries. a cross-national study of 25 european countries found that over time the negative gradient had remained strong in the mediterranean and post-communist countries (merz and liefbroer 2017). in great britain, women with degree-level qualifications still have smaller family sizes than those with lower levels of education and this difference in quantum appears to have widened in recent years (berrington et al. 2015). evidently the relationship between education and fertility is complex and varies not only over time, but also from country to country according to institutional contexts such as family policies, labour market characteristics and gender norms (liefbroer and corijn 1999; sobotka et al. 2017). it is suggested that educational differences in cohort fertility have all but disappeared in nordic countries because their welfare-state policies focus on supporting gender equality and allowing men and women to combine family and work (andersson et al. 2009; kravdal and rindfuss 2008). this paper investigates the effect of the increase in education on completed fertility, examining the completed fertility rate of five cohorts of women in australia born between 1952-56 and 1972-76 – cohorts which experienced large changes in education patterns. these cohorts also experienced considerable change in completed fertility. to consider these changes, we decompose the overall australian population studies 3 (2) 2019 gray & evans 3 change in completed fertility to analyse how it changed due to two factors: changes in the proportion of women in each education category, and changes in fertility of women in education categories. we note that many other changes in family formation also occurred for these cohorts including increases in non-marital childbearing, divorce and cohabitation without marriage. drawing on this analysis, we determine what proportion of the change in completed fertility across cohorts is due to the changing education patterns, and what proportion is due to changing fertility patterns within education categories. we begin by outlining recent trends in education, focusing on the period of 1960s to 1990s, the time period when most of the women in these cohorts would have been completing secondary education and gaining post-school qualifications. we then examine differences in completed fertility across education categories and how this has changed over time. 2. the expansion of education since the 1960s the 1960s marked the large-scale expansion of secondary schooling in australia. during the 1960s and 1970s there was growing political and public support for a system of comprehensive high schools which would enrol everyone regardless of merit or aptitude (campbell and proctor 2014). the influential 1973 karmel report called for reform in the education sector including establishing standards of achievement and ensuring adequate resourcing. it also addressed the existing gender inequality in male and female school completion. the report influenced a large increase in commonwealth funding during the whitlam government of the early 1970s. however, the economic crisis of the later 1970s and early 1980s, which was marred by high unemployment and inflation, led to restrictions on education expenditure (burke and spaull 2001). there are many different measures that can be used to show how education has expanded, but one of the most common is the participation rate at selected ages. the participation rate measures the proportion of the population at a selected age enrolled in an educational institution. the participation rate at age 16 from 1966 to 2000 is shown in figure 1. there was a dramatic rise in participation at age 16 throughout the 1960s, a plateau in the late 1970s and 1980s which may have been due to the economic crisis, followed again by an increase in the 1980s. in the mid-60s less than half of boys and girls aged 16 attended school. by 1970 this had increased to 55 per cent and 47 per cent respectively, and by 1980 to 56 and 60 per cent, with girls surpassing boys in the mid-1970s. another education indicator often used to study trends over time is apparent retention rate to year 12, which is the final year of high school completed at around age 18. this apparent retention rate is expressed as the number of students of a particular sex enrolled in year 12 as a percentage of the cohort of students of the same sex who first commenced secondary schooling (le and miller 2002). in 1971 the apparent retention rate to year 12 was 27 per cent for females and 34 per cent for males. by 1991 this had increased to 77 per cent for females and 66 per cent for males. from 1976 the percent of female students continuing to year 12 exceeded that of males, although this is partly explained by the greater uptake of trade and apprenticeship courses by males than females after completing year 10 (abs 1993 p. 95). 4 gray & evans australian population studies 3 (2) 2019 figure 1: participation rate in school at age 16 by sex, 1966-2000 source: anderson and vernon 1983; long et al. 1999; abs 2001, 2009. in line with increasing school completion already noted, there has also been an increase in the population with tertiary education. the increase in the total enrolment in higher education is shown in figure 2. part of the increase shown is a consequence of the progressive upgrading to degree status of courses which were at diploma level or lower. this includes many vocational-oriented qualifications in fields such as teaching, accounting, surveying, and nursing, originally provided by the former institutes of technology, teacher’s colleges, colleges of advanced education, and technical colleges (abs 1993). the fields of teaching and nursing are disproportionally female, so these changes had a direct impact on the percentage of women completing degree qualifications. figure 2: total enrolment in higher education by sex, 1966-2000 note: includes government teachers colleges from 1973 onwards. includes non-government teachers colleges from 1974 onwards. figures for years from 1985 to 1993 progressively include state-funded basic nursing students who would previously have been trained in hospitals. source: department of education, training and youth affairs (2001) australian population studies 3 (2) 2019 gray & evans 5 the other change in the education landscape is the changing nature of government funding models. in the early part of this period students paid tuition fees which were largely covered by merit-based commonwealth scholarships. in 1973 the whitlam government abolished fees. the impact of this is evident in a small but steep increase in tertiary enrolment, especially for women. in 1987 the government re-introduced fees through the higher education administrative charge (heac) and in 1989 introduced the higher education contribution scheme (hecs), an interest free incomecontingent loan for students to assist with payments of tuition fees (chapman 2011). these funding changes have clearly impacted total enrolment for men and women during the period of early adulthood for the cohorts covered in this study. 3. data and methods in order to examine the relationship between education and fertility we use data from the 2016 census. the census collects information on the three key aspects needed for this analysis: highest level of education, age, and number of children ever born. as seen in figures 1 and 2, the key period of educational expansion was in the 1960s to 1990s. to capture the experience of women going through secondary school and university during this period, we selected women born in a 19-year period from 1952 to 1976, split into five birth cohorts: 1952-56, 1957-61, 1962-66, 1967-71, 1972-76. at the time of the 2016 census they were aged 60-64, 55-59, 50-54, 45-49 and 40-44 respectively (table 1). table 1: cohort birth years and age at census cohort age at 2016 census year turned 16 1952-56 60-64 1968-72 1957-61 55-59 1973-77 1962-66 50-54 1978-82 1967-71 45-49 1983-87 1972-76 40-44 1988-92 detailed education categories are constructed from two variables: highest level of schooling and highest level of post-school qualifications gained. we were particularly interested in looking at detailed categories of educational attainment to gain a richer insight on the differences between high and low education. our measure of completed fertility is based on the census question asked of all females aged 15 and over: how many babies they have ever given birth to. using this ‘children ever born’ variable we calculate cohort fertility or average completed family size for each education category within each cohort. cohort completed fertility is calculated by multiplying the number children by the total number of women, including those who have no children. for the cohort born in 1972-76 who are aged 40-44, childbearing is not fully complete. however, we note that in 2017, just under 5 per cent of births were to mothers aged 40 or over (abs 2018), and more than half of these births were at 6 gray & evans australian population studies 3 (2) 2019 ages 40 and 41, so the overall impact of right-censoring and loss of information about future births for this group is relatively small. we begin by outlining the educational composition and completed fertility for each cohort. we then decompose the overall change in completed fertility to see how it changed due to two factors: the proportion of women in a particular education category, and the completed fertility of women in that education category. we use das gupta’s (1993) decomposition method developed as a stata program by li (2017). as we are only using one factor (education) the formula to calculate the effect of education and composition, respectively is: 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 𝐸𝐸𝐸𝐸𝑐𝑐𝑐𝑐𝐸𝐸𝑐𝑐𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝐸𝐸𝐸𝐸 = � 𝐸𝐸𝑖𝑖𝑖𝑖 𝐸𝐸𝑖𝑖 + 𝐸𝐸𝑖𝑖𝑖𝑖 𝐸𝐸𝑖𝑖 2 𝑖𝑖 × 𝐶𝐶𝐶𝐶𝐶𝐶𝑖𝑖𝑖𝑖 − � 𝐸𝐸𝑖𝑖𝑖𝑖 𝐸𝐸𝑖𝑖 + 𝐸𝐸𝑖𝑖𝑖𝑖 𝐸𝐸𝑖𝑖 2 𝑖𝑖 × 𝐶𝐶𝐶𝐶𝐶𝐶𝑖𝑖𝑖𝑖 𝐶𝐶𝑒𝑒𝐹𝐹𝐸𝐸𝐸𝐸𝐹𝐹𝐸𝐸𝐸𝐸𝐹𝐹 𝐹𝐹𝐸𝐸𝐸𝐸𝑒𝑒 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝐸𝐸𝐸𝐸 = � 𝐶𝐶𝐶𝐶𝐶𝐶𝑖𝑖𝑖𝑖 + 𝐶𝐶𝐶𝐶𝐶𝐶𝑖𝑖𝑖𝑖 2 𝑖𝑖 × 𝐸𝐸𝑖𝑖𝑖𝑖 𝐸𝐸𝑖𝑖 − � 𝐶𝐶𝐶𝐶𝐶𝐶𝑖𝑖𝑖𝑖 + 𝐶𝐶𝐶𝐶𝐶𝐶𝑖𝑖𝑖𝑖 2 𝑖𝑖 × 𝐸𝐸𝑖𝑖𝑖𝑖 𝐸𝐸𝑖𝑖 where cfr is the completed fertility rate, n is the population, i is education category, and 𝐸𝐸 and 𝑏𝑏 are the two populations being compared. for any two populations in this simple decomposition the difference between completed fertility rates is attributed to fertility or education composition, with these two components adding up to 100 per cent. 4. results 4.1. change in completed fertility as expected, due to the rise of education for women in the recent past, the educational composition of women in these cohorts is dramatically different (figure 3). the major change in education has been a decline in the proportion of women who only completed year 10 or below, from 30 per cent among the 1952-56 cohort to 10 per cent in the youngest cohort. in turn there has been a corresponding increase in women who have a bachelor’s degree, from 13 per cent in the earliest cohort to 23 in the latest cohort. those with complete high school (year 12) rose slightly, as did all categories of post-school qualification, except basic vocational. completed fertility has also changed across successive cohorts of women. overall, completed fertility has fallen from 2.23 in the 1952-56 cohort to 1.97 in the 1972-76 cohort. figure 4 shows how completed fertility has changed across the cohorts by education level. at higher levels of education completed fertility has declined more or less steadily, whereas for year 11 and year 10 or below, after a decline in the middle cohorts, we see a rise again in fertility for the most recent cohort. for example, for year 10, completed fertility fell from 2.44 among the 1952-56 cohort to 2.34 for women born in 1962-66. it then increased again to 2.43 for the 1972-76 cohort. this change of fertility for women in the lowest education categories are aligned with the dramatic decline of women in these education categories suggesting that the underlying composition of these groups has changed over time. australian population studies 3 (2) 2019 gray & evans 7 graduate or post graduate bachelors diploma or advanced diploma higher certificate basic vocational year 12 year 11 year 10 or below figure 3: percentage distribution of women by highest level of education and birth cohort source: abs 2019 – authors’ calculations graduate or post graduate bachelors diploma or advanced diploma higher certificate basic vocational year 12 year 11 year 10 or below figure 4: completed fertility by highest level of education and birth cohort source: abs 2019 – authors’ calculations 0 5 10 15 20 25 30 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 pe rc en ta ge 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 1.4 1.6 1.8 2.0 2.2 2.4 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 co m pl et ed fe rt ili ty 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 52 -5 6 57 -6 1 62 -6 6 67 -7 1 72 -7 6 cohort cohort 8 gray & evans australian population studies 3 (2) 2019 the pattern of change in completed total fertility from the 1952-56 cohort to the 1972-76 cohort is shown in figure 5. figure 5 also shows the contribution to completed fertility according to the women’s highest level of education. not only did completed total fertility decline across the cohorts but the contribution by each category also changed. most notably the contribution of completed fertility by women with year 10 or below schooling declined, whereas the contribution to completed fertility by women with a bachelor’s degree increased. the contribution of an education level to completed total fertility can decline if the proportion of women in that category decreases, or their completed fertility rate decreases, or both. in the next section we decompose the change in completed fertility rate to these two factors: compositional change in education categories and actual change in fertility within education categories. figure 5: relative contribution of education categories to overall completed fertility, by cohort source: abs 2019 – authors’ calculations 4.2. decomposing fertility rates and educational composition with this decomposition we can separately identify changes in completed fertility attributable to changes in the educational distribution as well as changes in fertility within each educational group. if, over time, the proportion of women in different educational groups changed but the completed fertility within each group remained the same then changes in total completed fertility would be 100 per cent due to changes in education composition. similarly, if the educational composition stayed the same, but fertility changed within the education groups, then 100 per cent of change in overall fertility could be attributed to fertility rate changes. the decomposition of completed fertility by cohort is shown in table 2. comparing the 1952-56 cohort with the 1957-61 cohort we see a decline of 0.07 children, from 2.23 to 2.16. of this decline, 72 per cent can be attributed to changes in fertility rates and 28 per cent to changes in educational composition. comparing the 1962-66 cohort with the 1957-61 cohort, there is a decline of 0.08 in completed fertility from 2.16 to 2.08. this decline was primarily due to declines in fertility across all education groups, with only 15 per cent attributable to changes in the composition of women across education categories. for the next two cohorts, completed fertility declined by 0.06 and this was 0.00 0.50 1.00 1.50 2.00 1952-1956 1957-61 1962-66 1967-71 1972-76 co m pl et ed fe rt ili ty year 10 or below year 11 year 12 basic vocational higher certificate diploma or advanced diploma bachelors graduate or post graduate australian population studies 3 (2) 2019 gray & evans 9 attributable fairly evenly due to declines in fertility and changes in the composition across education categories. the majority of the decline between the two most recent cohorts is attributable to changes in the composition across education categories. table 2: decomposition of completed fertility change attributable to: completed fertility of cohort completed fertility of previous cohort difference fertility rate effect (%) composition effect (%) 1952-56 2.23 1957-61 2.16 2.23 -0.07 72 28 1962-66 2.08 2.16 -0.08 85 15 1967-71 2.02 2.08 -0.06 53 47 1972-76 1.97 2.02 -0.05 31 70 total (1952-57 to 1972-61) -0.26 56 44 source: abs 2019 – authors’ calculations next we look in more detail at how fertility and education composition contributed to the decline in completed fertility between the cohorts. for each education category, figure 6 shows the effect on fertility of the changing proportion of women in that education category (proportion), and the changing fertility (rate) within each education group. the corresponding table can be found in the appendix. for example, as seen above, between the 1952-57 and 1957-61 cohorts completed cohort fertility declined by 0.07. between these two cohorts the education composition of women changed, and the fertility of women within education categories also changed. for these cohorts, the increase in the proportion of women with a graduate diploma, masters or phd contributed 0.013 to the difference in overall cohort fertility. the decline of fertility among women with a post-graduate degree contributed to -0.006, leading to an overall positive impact of 0.007. if we add up all the positive and negative effects of composition and fertility within each of the education categories it equals -0.07. for the two highest levels of educational attainment, postgraduate and bachelor, between every cohort comparison there was a positive effect on overall completed fertility due to increasing proportion of women with these degrees but a negative effect due to declining fertility in these education categories. however, the negative influence of declining fertility within the education categories was not large enough to offset the positive impact of increasing proportion of women with degrees leading to an overall positive effect on fertility. the increasing proportion of women with a bachelor’s degree had a particularly positive effect on completed fertility for the most recent cohorts, and the offsetting negative effect in the fertility rate among women with a bachelor’s degree was only minor in comparison. as a result, between the 1962-66 and 1967-71 cohort, women with a bachelor’s degree contributed 0.059 to the difference between overall completed fertility. the diploma level had a negligible effect on differences in fertility over time, as did certificate i and iv. for certificate iii and iv initially the increasing composition of women in the oldest cohorts had a positive effect, but in the in later cohorts the effect was minor. 10 gray & evans australian population studies 3 (2) 2019 figure 6: decomposition by cohort and detailed education categories source: abs 2019 – authors’ calculations (full results in appendix) australian population studies 3 (2) 2019 gray & evans 11 for year 12 the increasing composition coupled with very little change in their fertility rate led to an overall positive, though small, contribution to changes in completed fertility. for year 11 an interesting pattern emerges. for the early cohorts there was an increasing proportion of women in year 11 and a small but declining rate of fertility. in the most recent cohorts this switched and the proportion with year 11 declined, but the fertility of women with year 11 education increased. the overall impact on fertility was negative for the most recent cohorts. for year 10 we see the strongest effect of proportion and fertility rate. for each cohort comparison, the declining proportion in this education category had the effect of decreasing completed fertility. among the older cohorts in this group fertility also declined but in the younger cohorts it increased. 5. conclusions for older cohorts of australian women, attaining a degree was a rare occurrence and it was unusual to combine work and family. today the proportion of women with a degree has increased dramatically, and women with a degree are no longer such a selective group. one might therefore expect that the negative gradient between education and fertility would have weakened over time. in australia, we found no evidence of this. instead, as in britain, we find large and widening educational differences. the increasingly large proportion of women with university degrees are still experiencing declining fertility while women with year 11 or below schooling appear to have become an increasingly small and select proportion of the population with increasing fertility rates. these are also women with the lowest investment in human capital and the most precarious attachment to the labour force. in terms of the institutional support for women wanting to combine work and childbearing, australia still lags behind many european and scandinavian countries (heard and arunachalam 2015). the continued barriers to combining motherhood and work for educated women is likely one explanation for why in australia we continue to see educational differences in fertility. in terms of the effect overall, we find that for older cohorts the primary component of change in completed fertility was declining fertility. in the most recent cohort there is evidence that a composition effect due to changing educational trends is now the primary driver of declining fertility. in particular, the impact of the growing group of women with a bachelor’s degree and the shrinking proportion of women who have not completed high school reflects the growth in higher education enrolment shown in figure 2. using detailed education categories also enables us to capture the differences between high and low education. we find large differences in the pattern of fertility between the year 12, year 11 and year 10 or below-groups which are often grouped together in other studies as ‘no post school qualification’. while year 12 followed the same composition and rate trend as the bachelor’s level (increasing composition, declining fertility), the incomplete secondary groups were very different signalling an increasing marginalisation of women with very low levels of education. it is important to note that we use highest completed level of education at the time of the census as our indicator of educational attainment. this anticipatory approach could possibly lead to a bias in the estimates of the educational gradient as the attainment of the highest level of education may change across the reproductive life course and may have occurred after childbearing (hoem and 12 gray & evans australian population studies 3 (2) 2019 kreyenfield 2006). in addition, because we include women up to the age of 64 the results presented may also be biased by differential mortality to the extent that mortality varies by education (hoem and kreyenfield 2006). australia has one of the highest levels of tertiary education completion in the world. nearly 50 per cent of young adults (25-34 year-olds) in australia have attained a tertiary qualification, one of the highest across oecd countries and considerably above the oecd average of 43 per cent. given the significant increase in education, and the continued rising levels of education for women, future national fertility levels will in large part be determined by the childbearing of the increasingly large proportion of women with higher education (heard and arunchalam 2015). it is difficult to predict whether these differences will continue to diverge or whether they will follow european trends and begin to narrow. this will largely depend on the childbearing patterns of the increasingly select group who do not complete high-school, and the fertility of those with university degrees. both can be significantly influenced by supportive family policy. key messages • australia has seen a widespread increase in the level of education of women, and a corresponding decrease in completed fertility. • decomposition analysis allows a separation of the components of fertility decline into two parts: decline due to a change in the composition of education categories, and decline due to changes in fertility rates of cohorts. • for older cohorts, most of the decline is due to declining fertility rates. for the youngest cohort, the decline is due to changing education composition. • focussing on the different education levels provides additional insight into fertility change by level of education. incomplete secondary schooling has a declining effect on completed fertility while tertiary education has a substantial and growing contribution on the change in completed fertility. • overall, the gap between completed fertility by highest level of education is growing. acknowledgements the 2016 australian census data for this paper were made available by the australian bureau of statistics through their tablebuilder product. this research is funded by the australian research council (arc) (dp150104248). we would like to gratefully acknowledge the helpful comments provided by two referees 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2019 gray & evans 15 appendix table a: detailed decomposition of change in completed fertility due to composition and due to fertility rate, by highest level of education cohort 1952-56 to 1957-61 1957-61 to 1962-66 1962-66 to 1967-71 1967-71 to 1972-76 graduate diploma, masters or phd composition effect 0.013 0.008 0.02 0.022 fertility rate effect -0.006 -0.006 -0.002 -0.005 total effect 0.007 0.002 0.018 0.017 bachelor composition effect 0.028 0.021 0.064 0.089 fertility rate effect -0.008 -0.012 -0.005 -0.01 total effect 0.02 0.009 0.059 0.079 diploma or advanced diploma composition effect 0.025 0.011 0.016 0.001 fertility rate effect -0.005 -0.011 -0.009 -0.009 total effect 0.02 0.00 0.007 -0.008 certificate iii or iv composition effect 0.054 0.036 0.008 -0.002 fertility rate effect -0.004 -0.009 -0.009 -0.008 total effect 0.05 0.027 -0.001 -0.01 certificate i or ii composition effect 0.005 0.001 -0.008 0.00 fertility rate effect -0.003 -0.003 -0.002 0.00 total effect 0.002 -0.002 -0.01 0.00 year 12 composition effect 0.018 0.012 0.023 0.027 fertility rate effect -0.004 -0.004 -0.005 -0.001 total effect 0.014 0.008 0.018 0.026 year 11 or equivalent composition effect 0.01 0.009 -0.02 -0.039 fertility rate effect -0.002 -0.002 0.001 0.005 total effect 0.008 0.007 -0.019 -0.034 year 10 or below composition effect -0.147 -0.091 -0.115 -0.126 fertility rate effect -0.011 -0.014 0.001 0.011 total effect -0.158 -0.105 -0.114 -0.115 not stated composition effect -0.026 -0.019 -0.014 -0.01 fertility rate effect -0.006 -0.007 -0.002 0.00 total effect -0.032 -0.026 -0.016 -0.01 column total -0.07 -0.08 -0.06 -0.05 abstract background aims data and methods the study uses 2016 census data on the number of children ever born of five cohorts of women born between 1952 and 1976. decomposition is used to distinguish the effects of the two components. results the educational composition of women in these cohorts is dramatically different, with an increasing number of women having completed tertiary education in later cohorts. completed fertility has also changed across successive cohorts. we find that for ... conclusions despite tertiary education becoming much more common, fertility within this group remains lower than other education groups. while other countries have seen a narrowing of the gap in fertility rates between education groups, this pattern is not found ... key words education; fertility; fertility decline; children ever born; census; decomposition. 3. data and methods key messages acknowledgements references australian population studies 2017 | volume 1 | issue 1 | pages 73–85 © lomax and smith. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org an introduction to microsimulation for demography nik lomax* university of leeds andrew p. smith university of leeds *corresponding author. email: n.m.lomax@leeds.ac.uk. address: school of geography and leeds institute for data analytics, university of leeds, leeds ls2 9jt, united kingdom paper received 18 august 2017; accepted 18 october 2017; published 20 november 2017 abstract background microsimulation consists of a set of techniques for estimating characteristics and modelling change in populations of individuals. aims to demonstrate how microsimulation can be used by demographers who want to undertake population estimates and projections. data and methods we use data from the 2011 united kingdom (uk) census of population to create a synthetic population by age, sex and ethnic group. static and dynamic microsimulations and the visualisation of results are undertaken using the statistical package r. the code and data used in the static and dynamic microsimulation are available via a github repository. results a synthetic population in 2011 by age, sex and ethnicity was produced for the east london borough of tower hamlets, estimated from two census tables. a population projection was produced for each of these age, sex and ethnicity groups to 2021. we used a projection of the bangladeshi population to visualise population growth by middle-layer super output area (msoa) and to produce a population pyramid of estimates in 2021. conclusions we argue that microsimulation is an adaptable technique which is well suited to demography, for both population estimation and projection. although our example is applied to the east london borough of tower hamlets, the approach could be readily applied in australia, or any other country. key words microsimulation; static; dynamic; r code; demography; data visualisation; population estimation. http://www.australianpopulationstudies.org/ mailto:n.m.lomax@leeds.ac.uk 74 lomax n and smith a p australian population studies 1 (1) 2017 1. introduction this paper outlines how microsimulation can be of use to demographers as a method for the estimation and projection of populations. we outline what microsimulation is and how it has been used in a range of applications, from broader social science to demography specific examples. we provide two examples of how to apply microsimulation (with accompanying r code), firstly creating a synthetic population, and then projecting this population forward in time. while the examples presented in this paper relate to the united kingdom (uk), the methods could be readily applied to australia. we offer some examples of how the data can be visualised and analysed and a discussion of how the examples could be further extended. 2. what is microsimulation? microsimulation is an approach used to estimate the characteristics of a population from a range of attribute-rich data sources. micro refers to individual units (people, households, etc.) while simulation refers to the process of assigning attributes for those units. microsimulation can, for example, be used to allocate characteristics from a sample survey dataset to a larger population enumerated in a census. microsimulation can be used to create static or dynamic models. a static model is a way of synthesising data to produce an entire population estimate of individuals. dynamic microsimulation introduces time into the model and the ability to ‘age’ the static population. it is dynamic microsimulation which is used in population projections and to perform ‘what if’ scenario testing of policy or market interventions. the technique is often referred to as spatial microsimulation. essentially, the spatial element is concerned with allocating some form of geography to your individual or unit. we provide examples of static and dynamic microsimulation later in the paper. both are inherently spatial because they estimate people within specific areas. microsimulation has a wide range of utilities across a number of disciplines. for example, microsimulation has been used to model future elderly health care demand (clark et al. 2017), project educational attainment (nelissen 1991), commuting patterns (lovelace, ballas and watson 2014) and population projections (ballas et al. 2005). many of the applications of microsimulation we see in practice today stem from the work of orcutt (1957) and orcutt et al. (1961). spielauer (2011) provides a good overview of microsimulation applications for the social sciences (including the differences between static and dynamic models); li and o’donoghue (2013) provide a comprehensive discussion of dynamic microsimulation models implemented across a range of settings. for a comprehensive overview of spatial microsimulation see birkin and clarke (2011). ballas et al. (2005, p. 15) contend that microsimulation fundamentally is not that complicated an approach, noting that ‘even calculating simple social statistics such as life expectancy is a method that is similar to microsimulation’. when it comes to more complicated dynamic applications, bélanger and sabourin (2017) observe that microsimulation is an approach which has become increasingly popular with improved computing power and better availability of survey microdata. australian population studies 1 (1) 2017 lomax n and smith a p 75 3. why is microsimulation a useful technique for demographers? as a technique, demographers can make use of microsimulation to estimate and project populations and their attributes. in an age where more information is becoming available from disparate sources (e.g. censuses, surveys, administrative or commercial data), there is a need to synthesise this information if we wish to estimate populations with a range of attributes. the need for this attributerich information stems from the fact that we can produce more accurate models and make better recommendations if we know more about each individual. bélanger and sabourin (2017, p. xix) argue that micro models are superior to macro models because ‘the most powerful theoretical models for explaining human behaviour, such as decisions to have a child or migrate, operate at the level of the individual’. for a balanced assessment of microsimulation vis-a-vis macrosimulation models for population projection see van imhoff and post (1998, p. 134) who conclude that, while there are limitations (largely related to difficulty in implementation) ‘microsimulation can do certain things that macrosimulation cannot’. one of the key advantages they identify is the ability of microsimulation to perform in large state space – ‘the representation of the components of the system of interest’ (van imhoff and post 1998, p. 102) – where a large number of individual attributes would not be handled well by a macro model. wilson and rees (2005), in a review of population projection methods, conclude that microsimulation should be considered when projecting populations with multiple attributes. in the demographic literature, microsimulation has been used for a range of applications. for example, it was used by ruggles (1992) to correct missing data bias in historical demography, and by thomson et al. (2012) to estimate completed fertility in france when union formation and dissolution were varied in the simulation. models have been implemented in population projections: see, for example, smile (developed for ireland) (ballas et al. 2005) and moses (developed for the uk) (wu and birkin 2012). microsimulation models are also used to test the implications of policy change. ballas and clarke (2001) model the local impact of changes to national social policy in the uk; brown and harding (2002) provide an overview of a selection of microsimulation models examining policy decisions in australia. microsimulation is a technique which is useful outside the constraints of academia. increasingly microsimulation is being adopted to undertake official projections by national statistics agencies. mosart is used by statistics norway to project education, labour force and public pension benefits (fredriksen and stolen 2007); statistics canada’s projection model demosim uses microdata from the 2011 national household survey to produce estimates of future ethnocultural composition, aboriginal populations and labour force (bélanger and sabourin 2017); pensim is used by the uk department for work and pensions to estimate the future distribution of pensioner incomes (emmerson, reed and shephard. 2004); and sesim is used by the swedish ministry of finance for similar purposes (sundberg 2007). notwithstanding their utility, there are challenges and limitations associated with implementing microsimulation models which must be considered. first, a certain amount of technical expertise is required, although we explain in the next section that there are a range of options for implementing microsimulation models which are suitable for different levels of expertise. second, microsimulation can be computationally intensive. this was a key problem for early implementations of micro models; 76 lomax n and smith a p australian population studies 1 (1) 2017 however, advances in computing means that this is less of a limitation now than it once was. spielauer (2011, p. 18) outlines a third, more conceptual criticism: ‘randomness caused by accumulated errors and biases’. because microsimulation draws from a range of data sources, there is the potential for errors or biases in those data being extrapolated because of the level of detail required (or expected) from the microsimulation model. this randomness, similarly identified by van imhoff and post (1998) and wilson and rees (2005), is more acute in dynamic models because they are stochastic: results of a projection, for example, are randomly drawn from an expected distribution. brown and harding (2002, p. 1) highlight that microsimulation models are limited by design, assumptions, algorithms and data requirements but the solution is to ‘make these explicit and then interpret the results within the models' limitations and capacities’. this is advice which should be applied to any model, be it micro or macro in design. 4. how can microsimulation be applied? there are a multitude of ways to undertake microsimulation, from freely available custom software packages to writing your own model in a development language. bespoke packages are probably the easiest place to start. one excellent example is a program called the flexible modelling framework (fmf), created specifically to perform spatial microsimulation (harland 2013). the fmf has a graphical user interface (gui) which allows the user to select input files and specify required options and outputs, circumnavigating any requirement for the user to write their own code. the model is, however, only capable of static microsimulation. in the programming language r, there are several packages which have been developed to undertake microsimulation. the micsim package is one example which provides the required functionality to undertake microsimulation. for a comprehensive overview of how to use r to undertake spatial microsimulation, see lovelace and dumont (2016). an interim step between writing a program from scratch and an off-the-shelf gui is offered by statistics canada (bélanger and sabourin 2017). their framework, called modgen (model generator), implements an extension of the c++ language to help researchers build a model to their own specification, but does require some development skills to implement properly. for the examples presented in this paper we have chosen to write the code in r. this is because it offers the flexibility to incorporate data and functions of our choosing. also, because the source code is freely available, it offers researchers the option of adapting the code to their specific needs. a slightly longer initial outlay in terms of time and learning yields a more flexible and adaptable approach. 5. two examples: static and dynamic microsimulation we have produced an r package to demonstrate the techniques of both static and dynamic microsimulation with some example visualisations of the results. this package and associated documentation can be accessed via a github repository (see https://github.com/virgesmith/demographymicrosim). in this section, we give a description of the data and methodology, and provide some example illustrations from the results. detailed instructions on how to install and use the package are given in the readme.md file at the github link. the r package is self-contained in that it contains all the code and input data needed for the microsimulation. https://github.com/virgesmith/demographymicrosim australian population studies 1 (1) 2017 lomax n and smith a p 77 in the first example we use static microsimulation to create a base human population for the east london borough of tower hamlets from 2011 uk census data, estimating the population by geographical location, gender, age and ethnicity. in the second example we take this synthetic population and undertake a projection with dynamic microsimulation using detailed ethnicityspecific fertility and mortality data. we demonstrate ways to visualise the estimates using a map and population pyramid. 5.1 case study area the east london borough of tower hamlets makes an interesting case study area because it is one of the most diverse areas in the uk, both in terms of its ethnic composition and its socioeconomic structure. this part of london has seen successive waves of immigration and onward migration for centuries, including huguenots, jews, irish, bangladeshis and, more recently, migrants from eastern europe, somalia, eritrea and yemen. the borough is also a place of economic extremes: areas of poverty such as shadwell, whitechapel and poplar contrast with the financial district of canary wharf and the high-end ‘docklands’ riverside housing developments which have replaced the old working docks. our estimates are produced at middle-layer super output area (msoa) spatial resolution. msoas are a census geography where zones are aggregations of output areas, the smallest geography at which census data are released, and designed to provide consistent population counts across the country. msoas contain an average of just under 8,000 people. tower hamlets is split into 32 msoas and the borough’s total population is recorded as just over 250,000. the method outlined here could be adapted and applied to any other geography in the uk or elsewhere, so long as the data are available. the australian equivalent to these hierarchical census geographies are statistical areas (sas). sa2s have an average population of about 10,000 so are the nearest equivalent to the uk’s msoa geography. 5.2 input data the input data consist of two datasets, which are used for the static and dynamic microsimulation. we also provide geographical boundaries for the visualisation of results. the specific data used in our example are described in more detail in the following sections. however, in general terms, to undertake a static microsimulation as described in this paper the user will need one or more datasets containing full enumeration of the population of interest (e.g. from a census), disaggregated by some attributes. subsequent tables don’t need to provide full enumeration and some attributes need to match if drawing from a number of tables. to undertake dynamic microsimulation the user will additionally need demographic rates for the population of interest (e.g. from vital registration data). these need not be at the same spatial scale, as shown in our example. to replicate the visualisation of results, our code can be adapted to deal with any spatial system if shapefiles are available. 5.2.1 aggregate population data we use data from the uk 2011 census of population to create the microsimulated synthetic population. the 2011 census provides counts of people by area (in this case msoa), cross-tabulated by a number of characteristics. census data used here are sourced from nomis official labour market statistics (https://www.nomisweb.co.uk/) and contain public sector information licensed under the open government licence v3.0. https://www.nomisweb.co.uk/ 78 lomax n and smith a p australian population studies 1 (1) 2017 we have used the following tables: • dc2101ew: ethnic group by sex by age. after processing we have named this file sexageeth.csv in the github repository. it provides a count of persons by msoa by sex by age band by ethnicity. • dc1117ew: sex by single year of age. after processing we have named this file sexageyear.csv. it provides a count of persons by msoa by sex by single year of age. the data tables contain the following fields, where ‘persons’ is the count of each cross tabulation: • msoa: identification code for the 32 msoas within tower hamlets • sex: m (male) and f (female) • age band: 0-4, 5-7, 8-9, 10-14, 15, 16-17, 18-19, 20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64, 65-69, 70-74, 75-79, 80-84, 85+ • age: individual years up to 84, then a single 85+ category • ethnicity: ban (bangladeshi), bla (black african), blc (black caribbean), chi (chinese), ind (indian), mix (mixed), oas (other asian), obl (other black), oth (other), pak (pakistani), wbi (white british), who (white other). the categories for ethnicity have been aggregated from the original census categories in order to be consistent with the fertility and mortality data discussed below. figure 1 provides an extract from the two constraint tables. we can see that both tables contain useful information but are not consistent with each other. a b figure 1: extracts from (a) table sexageeth.csv and (b) table sexageyear.csv. 5.2.2 fertility and mortality rate data there is substantial variation in the rates of mortality and fertility for different ethnic groups (rees et al. 2009; norman et al. 2014), and it is important that our microsimulation captures this. we use ethnic-specific fertility and mortality rates produced as part of the newethpop project. newethpop has produced population projections for uk local authorities, disaggregated by age, sex and ethnic group, that capture the variation in demographic components which is mostly missed by other (nonethnic disaggregated) projections. for more information on the project see rees et al. (2017). projection results can be downloaded from www.ethpop.org. https://github.com/virgesmith/demographymicrosim/blob/master/data/sexageeth.csv https://github.com/virgesmith/demographymicrosim/blob/master/data/sexageyear.csv http://www.ethpop.org/ australian population studies 1 (1) 2017 lomax n and smith a p 79 rates by ethnicity and single year of age are available for the entire borough of tower hamlets. these rates are not differentiated at any smaller geographical scale. we use this information in the microsimulated population projection. note that while ethnic-specific migration data are used in the newethpop project, we do not use this in our paper. our aim is to keep the examples we present simple and reproducible. we provide the following files, which provide the ethnic-specific information, in the github repository: • towerhamletsfertility.csv, which is the ethnic and single year of age specific fertility rate for tower hamlets. • towerhamletsmortality.csv, which is the ethnic and single year of age specific mortality rate for tower hamlets. 5.2.3 geographical boundaries the code to map the results for the tower hamlets projection is also provided at github. this includes msoa boundaries made available by the office for national statistics under the open government licence v3.0. background map data are sourced from carto through openstreetmap under the open data commons open database license. 5.3 methodology in the following examples, microsimulation is necessary because we have information from different data sources which are not entirely consistent. while we have counts of people by single year of age by sex in one census table, the ethnic disaggregated counts from the other census table are only available for grouped age bands. the information on fertility and mortality rates is available for single year of age and sex, but is not geographically disaggregated below borough level. the aim here is to use static microsimulation to produce a population of individuals by sex, ethnicity, single year of age and msoa. this base population is then aged on using the ethnic-specific fertility and mortality rates in the dynamic microsimulation. 5.3.1 static microsimulation using microsimulation, we can generate a synthetic population that enumerates both ethnicity and single year of age for every individual. the sum of this population is entirely consistent with the input data: it will add up to both the ethnicity totals (by age band) and the population totals (by single year of age) for each geographical area and sex. for the microsimulation we use the humanleague r package that generates a population using quasirandom sampling of the marginal data (smith et al. 2017). iterative proportional fitting (ipf) achieves a similar goal, minimising statistical significance at the expense of not always producing a whole-number population in each (age, ethnicity) state, and thus requires some form of adjustment. see lomax and norman (2016) for a step-by-step guide to ipf. in our example, in any given area, for each gender and age band, we know the total persons of each ethnicity, and the total persons of each (single year of) age. we fill a table with people in such a way that: (1) there is a whole-number population for each age and ethnicity; (2) the totals for each age and ethnicity are correct; and (3) the population has a low statistical significance, i.e. age and ethnicity are not correlated. https://github.com/virgesmith/demographymicrosim/blob/master/data/towerhamletsfertility.csv https://github.com/virgesmith/demographymicrosim/blob/master/data/towerhamletsmortality.csv 80 lomax n and smith a p australian population studies 1 (1) 2017 the algorithm has three broad functional components: 1. load the input data and compute various data that will be required later (such as the categories, and a match between age band and age). 2. perform microsimulation for each geographical area and insert into the population. 3. perform checks on the synthesised population to ensure it is consistent with the input data. the result is a population of 254,096 individuals who have some combination of age, sex, ethnicity and msoa location. this is the base population which will be used for the dynamic projection. 5.3.2 dynamic microsimulation in this example we project the base population from 2011 to 2021. the projection uses a montecarlo simulation that assign births and deaths to the population based on the ageand ethnicityspecific fertility and mortality rates for the borough of tower hamlets. this type of methodology is described in van imhoff and post (1998). in this example, for each iteration (i.e. year) we draw two uniform independent random variates for each eligible person. we compare these values to the fertility and mortality rates for the appropriate age and ethnicity: if the first random variate is lower than the fertility rate, a birth is assigned to this person; if the second is lower, a death is assigned. only females have nonzero fertility rates, which are strongly age dependent. if the fertility rate is 0.1, this will result in on average one in ten of the population drawing a random lower number and having a birth assigned to them. for a mortality rate of 0.01, only 1 per cent of the population will on average draw a number lower than this. the simulation is discrete in that it operates in one-year intervals, and the user specifies the number of years to run the projection. in this relatively simple example, our population is 254,096 persons. each person exists in one of 66,048 possible states (32 [msoas] × 86 [ages] × 2 [genders] × 12 [ethnicities]). in a macrosimulation we would need to keep track of the number of people in each state (i.e. 66,048 values). however, in a microsimulation, we need to keep track of individuals and the states that they occupy. this requires storing about 1,000,000 values, since there are four separate categories. as more categories are added the number of states grows exponentially, while the storage required for individuals only grows linearly. it would only take the addition of one or two more categories before the number of states would exceed the population, and microsimulation would be a more efficient approach in terms of storage. note that the following assumptions are made in the model, which are reflected in the source code in the ‘microsimulate’ function (see lines 71–82 in microsimulation.r): • only single births occur (i.e. we assume that multiple births are factored into the fertility rate) • newborns have an equally probable chance of being male or female • the ethnicity and msoa of the newborn is the same as their mother’s • births occur before deaths – thus a newborn will survive if a parent dies within the same year • migration is not taken into account. see the final section of this paper for discussion about developing the example further. australian population studies 1 (1) 2017 lomax n and smith a p 81 the algorithm can be described as follows: 1. load the ethnicity-specific fertility and mortality rates. 2. randomly assign births and deaths to members of the population in a manner that is consistent with the fertility and mortality rates. 3. age the population by one year. 4. add newborns (aged zero) and remove the deceased from the population. 5. repeat from step 2 until the target year is reached. 5.4 visualisation figure 2: map of projected percentage population growth, 2011–2021 source: map tiles by carto under cc by 3.0. data by openstreetmap under odbl. note: low growth is blue and higher growth orange. to interpret the results, it is important to be able to visualise them effectively. the package provides functionality to calculate summary measures for visualisation. firstly growth (𝑔𝑇), 𝑔𝑇 = 𝑃𝑇 𝑃0 − 1 where 𝑃0 is the initial population and 𝑃𝑇 the final one. the value will be negative if the population shrinks, zero if unchanged, and positive if the population increases. the value is not annualised. secondly diversity, 𝑑 = 1 − 𝑛. var(𝐩) 82 lomax n and smith a p australian population studies 1 (1) 2017 where 𝑛 is the number of categories (i.e. ethnicities), 𝐩 a vector of populations in each category, and var is the sample variance. while numerous measures for diversity are used to explain population distributions (e.g. rees and butt 2004 use the diversity index), this measure has the useful properties that the value is: zero when the population is all in one category; one (1) when the populations in each category are equal; and essentially independent of the number of categories. we include code to produce maps of these data in the github repository. figure 2 (previous page) provides an example of total population growth between 2011 and 2021. figure 3: 2021 projected bangladeshi population pyramid, 2021 source: authors’ projections. we also provide a function to produce population pyramids of subsets of the base or projected population. figure 3 shows one of these population pyramids for the age and sex structure of the bangladeshi population in 2021. the code can be adapted to produce figures for other ethnic groups. 6. adaption and extension of the example the examples outlined in the previous section provide the building blocks needed for researchers to implement both static and dynamic microsimulation. in order to use the example in different contexts, researchers will want to adapt the data inputs to take in to account their own research interests. for example, fertility and mortality rates for different groups (e.g. stratified by socioeconomic status or health status) could replace ethnicity, and different geographic systems could replace the msoas used here. australian population studies 1 (1) 2017 lomax n and smith a p 83 there are also improvements which would make the microsimulation models more sophisticated. the first obvious extension is to include migration (both internal and international) in the model. this could be done by incorporating migration rates in a similar way to those used for fertility and mortality, but it is important to note that the model complexity and run time would be increased. for an overview of how complex and multifaceted a projection with dynamic microsimulation can be, see the work of holm et al. (2008) who describe the sverige model which not only incorporates migration, but also education, marriage, leaving home, divorce, employment and earnings. an individual simulated population cannot be considered an accurate prediction of the future. it is essentially an extrapolation that is subject to biases and uncertainties in the input data, the model assumptions and the random noise that is inherent in any monte-carlo simulation, which may amplify the initial biases. the second improvement, which would help to negate this problem, would be to perform a number of iterations of the model run and from these compute not a single value but a confidence interval for aspects of the final population. this would go some way towards alleviating the criticisms about randomness discussed in section 3. multiple runs of the model would give the researcher an idea about the variability of results, providing some indication of uncertainty which could be attached to projection estimates. this significantly increases the amount of computation required, but there are various statistical techniques available (outside the scope of this paper) which are more efficient than a brute-force approach. a third improvement is to test the sensitivity of the model to the input data or model assumptions. if there is a suspicion that some value or values in the input data are inaccurate or biased, perturbing these values (i.e. changing them by a small amount) and re-running the microsimulation can establish the sensitivity of the model to these inputs. if the projected population (or some aspect of it) is very similar the model can be considered insensitive to the input and the input’s accuracy may not be a major issue. conversely, if the projected population differs significantly the model is highly sensitive to the input, and perhaps the results cannot be accepted with much confidence. a final important consideration is the validation of model results. limitations in the amount of space available negate a discussion of model validation in this paper but for a good summary see ballas et al. (2005). 7. conclusion this paper has provided an overview of microsimulation as a technique which should be considered by demographers who are interested in estimating individuals within a population (through static models) and undertaking projections of those individuals (through dynamic models). we have argued that microsimulation is a technique which is useful for demographers and one which is becoming increasingly used as data, computing power and user support increases. our example is applied to the east london borough of tower hamlets but the approach could be readily applied in australia, or any other country for that matter, so long as appropriate data are available. useful next steps would be to look at the full r code provided for the examples outlined in this paper and have a go at implementing the model. the code can be adapted to suit the researchers’ requirements. 84 lomax n and smith a p australian population studies 1 (1) 2017 references ballas d and clarke g (2001) modelling the local impacts of national social policies: a spatial microsimulation approach. environment and planning c: government and policy 19(4): 587–606. ballas d, clarke g, dorling d, eyre h, thomas b and rossiter d (2005) simbritain: a spatial microsimulation approach to population dynamics. population, space and place 11(1): 13–34. bélanger a and sabourin p (2017) microsimulation and population dynamics: an introduction to modgen 12. the springer series on demographic methods and population analysis 43. switzerland: springer. birkin m and clarke m (2011) spatial microsimulation models: a review and a glimpse into the future. in: stillwell j and clarke m (eds) population dynamics and projection methods. netherlands: springer; 193–208. brown l and harding a (2002) social modelling and public policy: application of microsimulation modelling in australia. journal of artificial societies and social simulation 5(4), http://jasss.soc.surrey.ac.uk/5/4/6.html. clark s, birkin m, heppenstall a and rees p (2017) using 2011 census data to estimate future elderly heath care demand. in: stillwell j and duke-williams o (eds) the routledge handbook of census resources, methods and applications: unlocking the uk 2011 census. london: routledge; 305–319. emmerson c, reed h and shephard a (2004) an assessment of pensim2. london: ifs working papers, institute for fiscal studies (ifs) no. 04/21, doi: 10.1920/wp.ifs.2004.0421. fredriksen d and stolen n (2007) model 1: mosart (dynamic cross-sectional microsimulation model). in: gupta a and harding a (eds), modelling our future: population ageing, health and aged care. bingley: emerald group publishing limited; 433–437. harland k (2013) microsimulation model user guide: flexible modelling framework. uk: national centre for research methods (ncrm), ncrm working paper no. 06/13. holm e, holme k, lindgren u and mäkilä k. 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social science computer review 29(1): 9–20. sundberg o (2007) model 5: sesim (longitudinal dynamic microsimulation model). in: gupta a and harding a (eds), modelling our future: population ageing, health and aged care. bingley: emerald group publishing limited; 453–460. thomson e, winkler-dworak m, spielauer m and prskawetz a (2012) union instability as an engine of fertility? a microsimulation model for france. demography 49(1): 175–195. van imhoff e and post w (1998) microsimulation methods for population projection. population: an english selection 10(1): 97–138. wilson t and rees p (2005) recent developments in population projection methodology: a review. population, space and place 11(5): 337–360. wu b and birkin m (2012) agent-based extensions to a spatial microsimulation model of demographic change. in: heppenstall a, crooks t, see l and batty m (eds) agent-based models of geographical systems. netherlands: springer; 347–360. australian population studies 2018 | volume 2 | issue 2 | pages 33-58 © dennett 2018. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org an introduction to modelling population flows using spatial interaction models adam dennett* university college london * corresponding author. email: a.dennett@ucl.ac.uk. address: bartlett centre for advanced spatial analysis, university college london, gower street, london, wc1e 6bt, uk paper received 18 april 2018; accepted 10 may 2018; published 12 november 2018 abstract background spatial interaction models have been used for decades to explain and predict flows (of migrants, capital, traffic, trade etc.) between geographic locations. aims this paper will guide users through the process of fitting and calibrating spatial interaction models in order to understand, explain and predict internal migration flows in australia. data and methods internal migration data from the australian 2011 census of population and housing, which records people who have moved between greater capital city statistical areas over 5-year periods, is used to exemplify the modelling process. the r statistical software is used to process and visualise the data as well as run the models. results the full suite of wilson’s family of spatial interaction models is fitted to the internal migration data, revealing that distance and origin/destination populations are some of the most important influencing factors affecting internal migration flows. we see whether constraining the model to known flows about origins and/or destinations will improve the fits and model estimates. conclusions spatial interaction modelling has been a tool in the box of some population geographers for a number of decades. however, recent advances in more forgiving programming languages such as r and python now mean that this powerful modelling methodology is no longer only available to those who also possess advanced computer programming skills. this guide has exemplified the process of fitting and calibrating spatial interaction models on australian internal migration data, but the methods could easily be applied to other flow data sets in other contexts. key words spatial interaction model; gravity model; migration; r; estimation; visualisation; census; australia. http://www.australianpopulationstudies.org/ mailto:a.dennett@ucl.ac.uk 34 dennett australian population studies 2 (2) 2018 1. introduction in this introductory guide, you will learn how we can use spatial interaction models to model population flows for a variety of different purposes such as estimating unknown flows, predicting future patterns, understanding the drivers of those flows, or exploring the differences between the flows of different groups. the empirical example uses migration flows taken from the australian bureau of statistics (abs) 2011 census of population and housing (census), but the method is generic and could be used on any flow data (other population data such as commuting data or economic data such as flows of capital or trade, for example). the examples shown here will use the r software environment, and an accompanying practical walk-through guide will be referred to throughout this paper which can be accessed via the following link: https://rpubs.com/adam_dennett/376877. it can also be followed in its entirety if you would like to learn the code required for any of the models. 1.1 what constitutes a population flow? in fields such as population geography and demography, the population flows of interest are usually low-frequency migration or residential mobility moves. both assume some permanent change of residential address which can be either within a country (internal migration or residential mobility) or between countries (international migration). some scholars make a clear distinction between what they term ‘residential mobility’ (short-distance moves, usually within settlements or regions where individuals may retain the same social groups or job) and ‘internal migration’ (longer distance moves, which may involve changing jobs and social groups). however, in reality this is a continuum with no clear line demarking one or the other. most national censuses will simply refer to any internal move over any distance as ‘internal migration’. depending on where you are in the world, the proportion of a population changing their residential address in a given year is around 10 per cent, with most people only moving a handful of times in their lifetime. these population movements can be contrasted with high-frequency flows that occur on daily or weekly cycles. the commute to work or school or travel to the shops, while of interest to some population geographers, is frequently the domain of transport planners and analysts who are concerned with the impact of these moves on transport infrastructure and systems. 1.2. population flow data data related to these flows can vary. for migration, data captured by censuses or surveys tend to be ‘transitions’ over a period of time (a year, 5 years, 10 years) with a flow recorded if there is a difference between residential address between the start and the end of this period (rees 1977). transition data will not record multiple moves during a period and, as such, are simpler than movement data which record multiple moves. movement data can be found more commonly in population registers that track population changes continuously. commuting data, while frequently transitions derived from census returns, are increasingly being obtained from sources such as mobile phone cell tower connections and apps (erhardt and dennett 2017). in this guide we will use censusbased transition data; however, being aware of these other sources is important, particularly in a world that is looking increasingly to move away from censuses. https://rpubs.com/adam_dennett/376877 australian population studies 2 (2) 2018 dennett 35 1.3. why would we want to model population flows? as hinted in the introduction, there are a number of reasons for wanting to model population flows. in migration studies, in a number of papers by raymer and colleagues (raymer 2007; raymer, abel and smith 2007; raymer and abel 2008) as well abel (2010), willekens (1999) and dennett and wilson (2013), the problem of missing or incomplete data was addressed. pooler (1987) used similar models to tackle the problem of predicting migration, as did fotheringham et al. (2001). implicit in much of this modelling research is the evaluation of factors influencing the observed patterns – a paper by kim and cohen (2010) is more explicit in this regard. 1.4. how can we model population flows? population flows can be conceptualised as interactions between two entities – origins and destinations – which have different properties of emissivity and attractiveness (see lee 1966 for the classic paper on this topic in relation to migration). the strength of interaction is a function of these origin and destination properties and the negative influence of the cost (frequently some measure of distance, but equally could be financial, time or some other cost) that might be associated with travelling between them. this situation is analogous to that observed by newton when he defined the laws of gravity – the larger the entities interacting, the stronger the force of interaction; the further the distance between them, the weaker the interaction. hence the term ‘gravity model’ has been used and the equation applied in studying population flows for a long time. see zipf (1946) for one of the earlier applications of the model to population flows. over the years, various improvements have been made to the basic gravity model. perhaps the most important paper in this respect is by wilson (1971), where he introduces the idea of ‘constraints’ which force the flows or interactions estimated by the model to adhere to known information about the system. for example, there may be data on the total number of people leaving an origin or arriving at a destination (or both). in the basic gravity model, the flows estimated might exceed this known information, which is clearly an issue. by introducing constraints, it is possible to force the modelled flows to correspond to this known information, significantly improving accuracy. wilson called his new family of constrained models ‘spatial interaction models’. 2. modelling population flows in practice the basic theory behind spatial interaction or gravity models is not too difficult to comprehend. where the challenges begin is in running a spatial interaction model in practice. in the 1970s and 1980s, when spatial interaction modelling was being established as part of the tool kit for people working on spatial problems, running a model would require some fairly high-level computer programming knowledge. today, however, software has advanced and more forgiving languages such as python and r mean that spatial interaction models can be used as a tool by many more researchers. in this guide we will be using r, with details of the full implementation referred to in this paper found in an accompanying walk-through guide designed to be worked through while reading the text here. the guide includes all of the data and code you need to run a spatial interaction model, and can be https://rpubs.com/adam_dennett/376877 36 dennett australian population studies 2 (2) 2018 accessed via the link at the beginning of this paper1. if, however, you would like to explore these models in python, then oshan (2016) has written an excellent primer that is worth reading, while dan lewis has translated a similar r walk-through of mine into python using uk data2. for consistency, oshun’s notation is adopted in this paper. 2.1. data to illustrate the modelling exercise, migration data (derived from the answer about previous residence 5 years ago – therefore comprising 5-year transitions) from the 2011 census have been obtained. these data are at the greater capital city statistical area (gccsa) level, which is comprised of 15 zones (figure 1). figure 1: five-year migration flows between gccsas, 2006–2011 source: abs 2011 census. note: line weights indicative of volumes. 1 https://rpubs.com/adam_dennett/376877 2 https://github.com/danlewis85/ucl_casa_urban_simulation https://rpubs.com/adam_dennett/376877 https://github.com/danlewis85/ucl_casa_urban_simulation australian population studies 2 (2) 2018 dennett 37 accompanying the migration flows are variables for each origin and destination relating to: • total population • unemployment rate • median weekly income • percentage of households living in rented accommodation. these variables can be used to try and explain observed migration flows or predict flows if none are available. a table containing origin/destination pairs, the flows between them and these origin and destination specific variables can be observed in table 1 and is downloadable in the accompanying exercise. table 1: sample of pair-wise migration flow data with accompanying data relating to origin and destination characteristics origin destination flow origpop destpop orig unemp dest unemp orig med income dest med income orig % rented dest % rented greater sydney greater sydney 3,395,019 4,391,673 4,391,673 5.74 5.74 780.64 780.64 31.77 31.77 greater sydney rest of nsw 91,043 4,391,673 2,512,952 5.74 6.12 780.64 509.97 31.77 27.20 greater sydney greater melbourne 22,605 4,391,673 3,999,981 5.74 5.47 780.64 407.95 31.77 27.34 greater sydney rest of vic. 4,420 4,391,673 1,345,717 5.74 5.17 780.64 506.58 31.77 24.08 greater sydney greater brisbane 22,874 4,391,673 2,065,998 5.74 5.86 780.64 767.08 31.77 33.19 greater sydney rest of qld 27,447 4,391,673 2,253,723 5.74 6.22 780.64 446.48 31.77 32.57 greater sydney greater adelaide 5,829 4,391,673 1,225,235 5.74 5.78 780.64 445.53 31.77 28.27 greater sydney rest of sa 795 4,391,673 368,260 5.74 5.45 780.64 522.71 31.77 26.17 greater sydney greater perth 10,572 4,391,673 1,728,865 5.74 4.76 780.64 730.84 31.77 27.52 source: abs 2011 census 2.2. the ‘unconstrained’ / ‘total constrained’ spatial interaction model 2.2.1. the multiplicative modelling framework the classic gravity model, which estimates flows/interactions as a function of predictor variables (a model virtually identical to that used by zipf), can be written as follows: 𝑇𝑇𝑖𝑖𝑖𝑖 = 𝑘𝑘 𝑉𝑉𝑖𝑖 𝜇𝜇𝑊𝑊𝑗𝑗 𝛼𝛼 𝑑𝑑𝑖𝑖𝑗𝑗 𝛽𝛽 (1) this model can be rearranged and written in the multiplicative form more familiar from wilson’s 1971 paper: 𝑇𝑇𝑖𝑖𝑖𝑖 = 𝑘𝑘𝑉𝑉𝑖𝑖 𝜇𝜇𝑊𝑊𝑖𝑖 𝛼𝛼𝑑𝑑𝑖𝑖𝑖𝑖−𝛽𝛽 (2) 38 dennett australian population studies 2 (2) 2018 where: 𝑇𝑇𝑖𝑖𝑖𝑖 is the transition/trip or flow, 𝑇𝑇, between origin 𝑖𝑖 (always the rows in a matrix) and destination 𝑗𝑗 (always the columns in a matrix). if you are not overly familiar with matrix notation, the 𝑖𝑖 and 𝑗𝑗 are just generic indexes to allow us to refer to any cell in the matrix. 𝑉𝑉 is a vector (a 1 dimensional matrix – or, if you like, a single line of numbers) of origin attributes which relate to the emissivity of all origins in the dataset, 𝑖𝑖 – this could be any of the origin-related variables in table 1. 𝑊𝑊 is a vector of destination attributes relating to the attractiveness of all destinations in the dataset, 𝑗𝑗 – similarly, this could be any of the destination related variables in table 1. 𝑑𝑑 is a matrix of costs (frequently distances – hence, d) relating to the flows between 𝑖𝑖 and 𝑗𝑗. 𝑘𝑘, 𝜇𝜇, 𝛼𝛼 and 𝛽𝛽 are all model parameters to be estimated. 𝛽𝛽 is assumed to be negative, as with an increase in cost/distance we would expect interaction to decrease. wilson’s term for this basic gravity model is the ‘unconstrained’ model. however, 𝑘𝑘 is a constant of proportionality and forces all flow estimates to add up to the total number of flows observed in a system. this leads to this particular model being more accurately described as a ‘total constrained’ model, where: 𝑘𝑘 = 𝑇𝑇 ∑ ∑ 𝑉𝑉𝑖𝑖 𝜇𝜇𝑗𝑗𝑖𝑖 𝑊𝑊𝑗𝑗 𝛼𝛼𝑑𝑑𝑖𝑖𝑗𝑗 −𝛽𝛽 (3) and 𝑇𝑇 is the sum of our matrix of observed flows or: 𝑇𝑇 = ∑ ∑ 𝑇𝑇𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 (4) in plain language, this is just the sum of all observed flows divided by the sum of all of the other elements in the model. if we use distance as a basic measure of cost, then the simplest distance to measure is the euclidean distance between the centroids of the zones for which you have data. in the accompanying walkthrough exercise, the process of generating a distance matrix from a set of gccsa boundaries is demonstrated using the spdists() function in r. observing equations 1 and 2 above you would be forgiven for asking how the values for the four parameters are known or estimated. one solution could be to simply insert some arbitrary or expected values as parameters. this becomes more feasible once we understand what the parameters are in reality: they relate to the scaling effect/importance of the variables with which they are associated. most simply, where the effects of origin and destination attributes on flows scale in a linear fashion (i.e. for a 1 unit increase in, say, population at origin, we might expect a 1 unit increase in flows of people from that origin; or for a halving in average salary at destination, we might expect a halving of migrants), then the parameter/scaling factor for our origin variable would equal 1, e.g. μ = 1 and α = 1. in newton’s original gravity equation the negative influence of distance is not linear. rather, it follows a power law. for example, where β = -2 for a 1 unit increase in distance, we have a 1-2 (or 1) australian population studies 2 (2) 2018 dennett 39 unit decrease in interaction/flow. for a 2 unit increase in distance, we have 2-2 (0.25 or 1/4) of the interaction, for a 3 unit increase, 3-2 (0.111) of the interaction and so on. we can check to see if μ = 1 and α = 1 and β = -2 are a good or poor guess by looking at our data and plotting observed flows against each variable and seeing whether the value of these variables raise to these powers (figure 2). reviewing the three graphs at figure 2a, 2b, 2c, it can be observed that -2 looks like a fairly good estimate for β with the red modelled line matching quite closely the observed relationship between migration flows and distances. 1 also looks like a fair estimate of μ for at least some of the relationship between origin population and migration flows; however, it appears that there is little discernible visible relationship between destination median incomes and migration flows, so the value of α may be of little consequence. if we accept that these first parameter estimates are plausible, then they can be inserted into equation 2 to generate a first set of estimates. such a set of estimates, where k=3.28, μ = 1, α=1 and β=-2, are shown in table 2. these can be compared with the observed flows in table 3. manual inspection of the flows reveals that in some cases the estimates are not too far from the observed flows, but in others we can clearly see that the estimates are a long way out. whilst it is ok to ‘eyeball’ small flow matrices like these, when you have much larger matrices, another solution is required to test the so-called ‘goodness-of-fit’. there are a number of ways to do this but two of the most common are to calculate the coefficient of determination (r2) or the square root of mean squared error (rmse). anyone who has run a linear regression model before will have come across r2 but rmse may be less familiar. there are other methods and they all do more-or-less the same thing: compare the modelled estimates with the real data and represent the degree of agreement with a single number. r2 is popular as it is quite intuitive and can be compared across models. rmse is less intuitive, but some argue is better for comparing changes to the same model. guidance on how to quickly calculate r2 and rmse can be found in the accompanying practical guide. in this initial case, the r2 value is 0.18. this tells us that this first model accounts for about 18 per cent of the variation of flows in the system – not brilliant, but a starting point nevertheless. as a result, two immediate questions emerge: can we improve these estimates? can we tell which predictor variables are best? fortunately, the answer to both of these questions is ‘yes’. one way that we can begin to answer both of these questions is through the process of model calibration. 40 dennett australian population studies 2 (2) 2018 (a) distance note: red line is distance or 𝑑𝑑𝑖𝑖𝑖𝑖−𝛽𝛽 estimate where 𝛽𝛽 = -2 (b) origin population note: red line is origin population or 𝑉𝑉𝑖𝑖 𝜇𝜇estimate where 𝜇𝜇 = 1 (c) destination median income note: red line is destination median income or 𝑊𝑊𝑖𝑖 𝛼𝛼estimate where 𝛼𝛼 = 1 figure 2: the relationship between migration flows and three predictor variables australian population studies 2 (2) 2018 dennett 41 table 2: modelled flows from the initial total constrained gravity model with crude estimated parameters origin / destination 1gsyd 1rnsw 2gmel 2rvic 3gbri 3rqld 4gade 4rsau 5gper 5rwau 6ghob 6rtas 7gdar 7rnte 8acte (all) 1gsyd 0 47944 12607 15513 22050 3346 5187 3522 1012 1325 5627 7789 1386 1395 193311 322014 1rnsw 41995 0 8089 12786 11218 3039 5467 3675 721 1008 2566 3703 1021 1138 42659 139085 2gmel 21972 16095 0 373099 5627 2040 13506 4665 1294 1539 15973 29621 1221 1271 62311 550234 2rvic 7325 6893 101083 0 2014 784 6705 1971 465 570 3652 6304 448 481 18995 157690 3gbri 10556 6131 1546 2041 0 3035 1256 1293 397 573 955 1259 791 771 6639 37243 3rqld 3002 3113 1050 1491 5688 0 1508 2718 615 1118 630 844 2101 2759 2873 29510 4gade 2536 3051 3788 6941 1283 821 0 5788 653 858 1300 1973 543 657 4041 34233 4rsau 441 525 335 523 338 379 1483 0 250 462 172 241 275 439 569 6432 5gper 425 346 312 414 349 288 562 839 0 4637 273 356 730 604 535 10670 5rwau 156 136 104 142 141 147 207 434 1299 0 81 107 523 508 190 4175 6ghob 478 249 778 657 169 60 226 116 55 58 0 25438 46 43 876 29249 6rtas 724 393 1579 1240 244 87 375 179 79 84 27825 0 65 62 1416 34352 7gdar 33 28 17 23 39 56 26 52 41 105 13 17 0 326 36 812 7rnte 42 39 22 31 49 93 41 107 44 131 15 20 417 0 47 1098 8acte 13901 3502 2571 2893 997 230 594 327 92 116 742 1096 110 112 0 27283 (all) 103586 88445 133881 417794 50206 14405 37143 25686 7017 12584 59824 78768 9677 10566 334498 1384080 source: abs 2011 census. notes: greater sydney = 1gsyd; rest of new south wales = 1rnsw; greater melbourne = 2gmel; rest of victoria = 2rvic; greater brisbane = 3gbri; rest of queensland = 3rqld; greater adelaide = 4gade; rest of south australia = 4rsau; greater perth = 5gper; rest of western australia = 5rwau; greater hobart = 6ghob; rest of tasmania = 6rtas; greater darwin = 7gdar; rest of northern territories = 7rnte; australian capital territory = 8acte 42 dennett australian population studies 2 (2) 2018 table 3: original flow data for comparison origin / destination 1gsyd 1rnsw 2gmel 2rvic 3gbri 3rqld 4gade 4rsau 5gper 5rwau 6ghob 6rtas 7gdar 7rnte 8acte (all) 1gsyd 0 91043 22605 4420 22874 27447 5829 795 10572 2127 1654 1984 1992 828 10658 204828 1rnsw 53568 0 12418 13072 21289 35191 3613 1587 4999 3295 978 1885 2252 1431 15766 171344 2gmel 15569 11094 0 70264 13055 16164 6017 1292 10111 2570 2126 2553 2029 1004 4727 158575 2rvic 2528 11968 47988 0 4328 10110 3468 2217 3449 2597 667 1428 1548 721 1362 94379 3gbri 12333 16056 13080 4249 0 84649 3044 818 4810 1796 1388 2295 1802 905 3127 150352 3rqld 11629 26699 12284 7566 74412 0 3772 1758 6583 4688 1479 3086 3126 2142 3125 162349 4gade 5415 3517 8803 3188 5449 6178 0 25679 3831 1230 598 872 1843 927 1995 69525 4rsau 477 1490 1154 2439 824 2631 22020 0 1051 1354 148 429 679 484 185 35365 5gper 6523 4064 11721 2931 5086 7019 2625 865 0 41332 1022 1802 1305 416 1675 88386 5rwau 714 2241 1490 1811 1141 4333 808 982 42149 0 277 1161 1093 627 251 59078 6ghob 1221 998 3014 624 1307 1810 532 111 901 365 0 5019 195 113 564 16774 6rtas 1029 1871 2637 1647 1543 2884 658 343 1210 1028 7214 0 272 164 288 22788 7gdar 1237 2185 1957 1481 2763 5107 2111 641 2149 949 239 333 0 1998 824 23974 7rnte 406 1432 700 792 896 3018 1296 961 699 826 96 213 2684 0 229 14248 8acte 7065 16829 5930 1994 5225 6968 2657 1091 2212 1110 466 480 3304 56779 0 112110 (all) 119714 191487 145781 116478 160192 213509 58450 39140 94726 65267 18352 23540 24124 68539 44776 1384075 source: abs 2011 census australian population studies 2 (2) 2018 dennett 43 2.2.2. regression modelling framework calibration is the process of adjusting parameters in the model to try and get the estimates to agree with the observed data as much as possible. adjusting the parameters is the sort of iterative process that computers are particularly good at and the goodness-of-fit statistics can be used to indicate when the optimum solution is found. historically this process required a researcher with the requisite programming skills to write a computer algorithm to iteratively adjust each parameter, check the goodness-of-fit, and then start all over again until the goodness-of-fit statistic was maximised/minimised. there are various well-established routines that can achieve this, such as the newton-raphson algorithm, but without the necessary programming skills this can be a serious barrier and probably why spatial interaction modelling was the preserve of a few specialists for so long. however, since the early days of spatial interaction modelling, a number of useful developments have occurred. perhaps the most important in the context of calibration is the fact that it is possible to turn the multiplicative model in equation 2 into an additive model. taking the logarithms of both sides of equation 2, you end up with the following equation: ln𝑇𝑇𝑖𝑖𝑖𝑖 = 𝑘𝑘 + 𝜇𝜇ln𝑉𝑉𝑖𝑖 + 𝛼𝛼ln𝑊𝑊𝑖𝑖 − 𝛽𝛽ln𝑑𝑑𝑖𝑖𝑖𝑖 (5) what we have now is a regression model. anyone who has been introduced to regression models in introductory statistics classes will be aware that there are various pieces of software available to us to run regressions (such as r) and calibrate the parameters (or ‘estimate the coefficients’ in the language of statistics), so expert programming skills are no longer required. there are some papers that are worth reading at this point if you would like to learn more. perhaps the best is by flowerdew and aitkin (1982). one of the key points that flowerdew and aitkin make is that the model in equation 5 (known as a log-normal model) has various problems associated with it, which mean that the estimates produced might not be reliable. the paper (and also wilson’s 1971 paper) details these issues; however, the salient point is that the way around many of these issues is to re-specify the model, not as a log-normal regression but as a poisson or negative binomial regression model. the flows that spatial interaction models deal with (such as migration or commuting) relate to nonnegative integer counts (you cannot have negative people moving between places and you cannot normally – if they are alive! – have fractions of people moving either). as such, the probability of migrating or commuting is not described by a continuous (normal) probability distribution (the distribution which underpins the error distribution in standard linear regression models), but a discrete probability distribution such as the poisson distribution or the negative binomial distribution (of which the poisson distribution is a special case). there is a family of generalised linear models, but in the analysis of migration and other population flows poisson and negative binomial regression models have been used most frequently (abel 2010; congdon 1993, 1988; crymble, dennett and hitchcock 2017; flowerdew 2010, 1982; flowerdew and aitkin 1982; shen 2017, 2015; willekens 1999). the differences between the two are technical, but some, including congdon (1993), argue that negative binomial models should be used over poisson due to a statistical phenomenon known as overdispersal. for ease of explanation here we will 44 dennett australian population studies 2 (2) 2018 continue with the poisson model, but be aware that in practice a negative binomial model may be better. in the migration modelling literature others, such as raymer (raymer 2007; raymer, abel and smith 2007; raymer and giulietti 2010; rogers and raymer 1998), have used what are described as loglinear models. these are exactly the same as poisson models with the distinction that poisson models will usually contain both continuous and categorical predictor variables, whereas log-linear models will only contain categorical predictors. for a two-dimensional population flow matrix between origins and destinations, these categorical predictors would generally be the origin and destination zones – in effect we would have a two-dimensional contingency table. the analysis of contingency tables is well established in statistics and as such has its own lexicon. in log-linear modelling terminology, these origin and destination zones would be described as the ‘main’ or ‘fixed’ effects and are equivalent to the ‘constraints’ that will be introduced later on in this paper. this discussion of poisson, log-linear and spatial interaction models is included here for the purpose of highlighting that in the migration modelling literature it can be particularly confusing when reading papers by different authors who all use very different terminology and modelling paradigms. iterative proportional fitting (ipf) is another term that may appear when researching papers in this area (lomax and norman 2016). the salient point is that all of the models are essentially doing the same thing, but the papers in which they are outlined ascribe to different definitional conventions. how is the poisson distribution different to a normal distribution? aside from them describing different frequency/probability distributions, they behave differently for different sets of observations. below are two histograms (figure 3). the first is a random variable with a normal distribution, with a mean of 75 and a standard deviation of 5; the second is a histogram of poisson distributed variable with the same mean (poisson distributions have only one parameter – the mean). you will notice that they look broadly similar. however, with a poisson distributed variable, when the mean (𝜆𝜆 lambda) changes, so does the shape of the frequency distribution. as the mean gets smaller, and this is often the case with flow data where small flows are very likely, the distribution starts to look a lot more like a skewed or log-normal continuous distribution. the key point is that it is not a continuous distribution but a discrete (poisson) distribution. figure 4 plots a frequency distribution for a discrete variable with a small mean. the shape of the histogram is very similar to a positively skewed continuous distribution. for any system of population flows between a matrix of origins and destinations, the flows will have a mean value of 𝜆𝜆𝑖𝑖𝑖𝑖 which will normally be quite low and will dictate the distribution. plotting the frequency distribution of migration flows between our australian gccsas (excluding within-area flows – figure 5), reveals a histogram which looks like a skewed normal or, more accurately, a poisson distribution with a small mean. australian population studies 2 (2) 2018 dennett 45 (a) random variable with a normal distribution (b) random variable with a poisson distribution figure 3: normal and poisson distributions figure 4: poisson distribution with a small mean 46 dennett australian population studies 2 (2) 2018 figure 5: frequency distribution of migration flows (excluding intra-zonal flows) between gccsas in all of this discussion about frequency/probability distributions, it can be easy to lose track of the purpose for understanding all of this. perhaps the easiest way to remind ourselves of the purpose is in understanding the basics of what a regression model is trying to do. at its most simple a regression model is nothing more than a line of best fit drawn through a cloud of observations. if we think of a spatial interaction model as partially representing the relationship between volume of flow and cost of interaction (distance), then we would expect to see a straight line between flow volumes and distance. figure 2a shows that when plotting raw flows against distance, the relationship cannot be represented by a straight line. however, if both the flows and the distance are logged, as in equation 5, a plot similar to the one below in figure 6 is produced. it might not be a clear straight-line relationship, but there is certainly a suggestion that the blue regression line does represent the underlying relationship between migration flows and distance. figure 6: relationship between log(distance) and log(migration flows) between gccsas australian population studies 2 (2) 2018 dennett 47 now the discussion in the previous session indicates that the 𝑦𝑦 variable in our model is not logged as in the graph above. however, it can still be modelled using something like the blue line if we assume a poisson distribution. equation 5 can now be re-specified as a poisson regression model. instead of the dependent variable being ln𝑇𝑇𝑖𝑖𝑖𝑖, it is now the mean of the poisson distribution 𝜆𝜆𝑖𝑖𝑖𝑖 and the model becomes: 𝜆𝜆𝑖𝑖𝑖𝑖 = exp(𝑘𝑘 + 𝜇𝜇ln𝑉𝑉𝑖𝑖 + 𝛼𝛼ln𝑊𝑊𝑖𝑖 − 𝛽𝛽ln𝑑𝑑𝑖𝑖𝑖𝑖) (6) what this model says is 𝜆𝜆𝑖𝑖𝑖𝑖 (the dependent variable – the estimate of 𝑇𝑇𝑖𝑖𝑖𝑖) is logarithmically linked to (or modelled by) a linear combination of the logged independent variables in the model. using equation 6, a poisson regression model can be fitted to produce estimates of 𝑘𝑘, 𝜇𝜇, 𝛼𝛼 and 𝛽𝛽 – or put another way, we can use the regression model to calibrate our parameters. it is very straight forward to run a poisson regression model in r using the glm() (generalised linear models) function. the code to do this can be found in the accompanying guide. delving into the depths of the glm() function documentation will reveal that the parameters are calibrated though an ‘iteratively re-weighted least squares’ algorithm. this essentially fits lots of lines similar to that in figure 6 to the data until it finds the best one. it continually adjusts the parameters to minimise the error between the observed and expected (blue line) values using some goodness-of-fit measure, not dissimilar to an r2 or rmse. running the model will produce some output similar to that shown below in box 1. call: glm(formula = flow ~ log(vi1_origpop) + log(wj3_destmedinc) + log(dist), family = poisson(link = "log"), data = mdatasub, na.action = na.exclude) deviance residuals: min 1q median 3q max -177.78 -54.49 -24.50 9.21 470.11 coefficients: estimate std. error z value pr(>|z|) (intercept) 7.1953790 0.0248852 289.14 <0.0000000000000002 *** log(vi1_origpop) 0.5903363 0.0009232 639.42 <0.0000000000000002 *** log(wj3_destmedinc) -0.1671417 0.0033663 -49.65 <0.0000000000000002 *** log(dist) -0.8119316 0.0010157 -799.41 <0.0000000000000002 *** -- signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 (dispersion parameter for poisson family taken to be 1) null deviance: 2750417 on 209 degrees of freedom residual deviance: 1503573 on 206 degrees of freedom aic: 1505580 number of fisher scoring iterations: 5 box 1: model output including calibrate parameters from r glm() implementation of equation 6 https://rpubs.com/adam_dennett/376877 48 dennett australian population studies 2 (2) 2018 box 1 contains various pieces of information. the ‘call’ section at the top is the code used to run the model in r. then, under the ‘coefficients’ section, are the values for the four calibrated parameters in the model. in our original model, we estimated the four parameters as follows: 𝑘𝑘 = 3.28, 𝜇𝜇 = 1, 𝛼𝛼 = 1 and 𝛽𝛽 = −2 after fitting the poisson model, the values for the parameters can be found in the ‘estimate’ column. they change to: 𝑘𝑘 = 7.195, 𝜇𝜇 = 0.59, 𝛼𝛼 = −0.17 and 𝛽𝛽 = −0.81 the regression model also produces some other useful pieces of output. the p-values in the last column reveal that all variables have a highly (***) statistically significant influence on migration flows, with the z-scores (standardised coefficients) revealing that distance has the most (negative) influence on the model followed by origin population, with destination income only a small influence on the flows, and a counterintuitive one at that, with increases in destination income resulting in decreases in migration flows. in the accompanying practical guide, it is shown how these parameter values can be inserted directly back into equation 6 to produce a new set of estimates similar to those in table 1. the r2 value for this new matrix improves to 0.32, meaning that by simply calibrating the model parameters on observed data, we are able to explain around 14 per cent more of the variation in the migration flows in our system. 2.2. constrained spatial interaction models returning to wilson’s (1971) seminal paper, he introduces a full family of spatial interaction models of which the unconstrained model is just the start. of course, since then, there have been all manner of incremental advances and alternatives (dennett and wilson 2013; fotheringham 1983; pooler 1994; stillwell 1978). however, in this section we will concentrate on wilson’s original family – the production (origin) constrained model; the attraction (destination) constrained model; and the doubly constrained model – but show how the poisson regression framework can be used as with the unconstrained model. recalling the unconstrained/total constrained model above (table 1), while the total flows in the estimates equalled the total observed flows, none of the estimates sum to the observed in-migration and out-migration totals (the margins of the matrix). wilson’s real contribution to the field was in noticing that this unconstrained model was sub-optimal as it did not make use of all of the available information in the system being studied. where there is a full flow matrix to calibrate parameters, then it is possible to incorporate the row (origin) totals, column (destination) totals or both origin and destination totals to constrain flow estimates to these known values. there are various reasons for wanting to do this in different flow modelling contexts, for example: a) if the researcher is interested in flows of money into businesses or customers into shops, then they might have information on the amount of disposable income and shopping habits of the people living in different areas, perhaps from loyalty card data. this is known information about origins and so it would be logical to constrain the estimates from a spatial interaction model to https://rpubs.com/adam_dennett/376877 australian population studies 2 (2) 2018 dennett 49 this known information. other information about the attractiveness of shops and businesses (store size, variety/specialism of goods etc.) can then be used to estimate how much money/customers a new store opening in the area might make/attract or, if a new out-of-town shopping centre opens, how much it might affect the business of shops in the town centre. this is what is known in the literature as the ‘retail model’ and is perhaps the most common example of a production (origin) constrained spatial interaction model. b) other researchers might be interested in understanding the impact of a large new employer in an area on the flows of traffic in the vicinity or on the demand for new worker accommodation nearby. a good example of where this might be the case is with large new infrastructure developments like airports. for example, before the go-ahead for the new third runway at heathrow airport in london, england was given, one option being considered was a new runway in the thames estuary. if a new airport was built here, what would the potential impact on transport flows be in the area and where might workers commute from? this sort of scenario could be tested with an attraction (destination) constrained spatial interaction model where the number of new jobs in a destination is known (as well as jobs in the surrounding area). the model could also be used to estimate where the workers will be drawn from and their likely travel-to-work patterns. these models are known as land use transport interaction (luti) models and have a well-established history in urban planning. c) other researchers might be interested in understanding the changing patterns of commuting or migration over time. data from a census provides an accurate snap-shot of migrating and commuting patterns, but only periodically. in these full data matrices, information about both the numbers of commuters/migrants leaving origins and arriving at destinations and the interactions between them is known. constraining model estimates to this known information at origin and destination allows various things to be examined, including: i. the ways that the patterns of commuting/migration differ from the model predictions – where might there be more migrant/commuter flows than expected? ii. how the model parameters vary over time – for example, how does distance/cost of travel affect flows over time? are people prepared to travel further or less distance than before? 2.2.2. the production constrained model recall the unconstrained model from equation 2. a production constrained model constrains estimates to known information about the origins and so replaces the terms 𝑘𝑘 and 𝑉𝑉𝑖𝑖 𝜇𝜇 to produce the following model: 𝑇𝑇𝑖𝑖𝑖𝑖 = 𝐴𝐴𝑖𝑖𝑂𝑂𝑖𝑖𝑊𝑊𝑖𝑖 𝛼𝛼𝑑𝑑𝑖𝑖𝑖𝑖−𝛽𝛽 (7) where: 𝑂𝑂𝑖𝑖 = ∑ 𝑇𝑇𝑖𝑖𝑖𝑖𝑖𝑖 (8) and: 𝐴𝐴𝑖𝑖 = 1 ∑ 𝑊𝑊𝑗𝑗 𝛼𝛼 𝑗𝑗 𝑑𝑑𝑖𝑖𝑗𝑗 −𝛽𝛽 (9) 50 dennett australian population studies 2 (2) 2018 in the production constrained model, 𝑂𝑂𝑖𝑖 does not have a parameter as it is a known constraint. 𝐴𝐴𝑖𝑖 is known as a balancing factor and is a vector of values which relate to each origin 𝑖𝑖 which do the equivalent job as 𝑘𝑘 in the unconstrained/total constrained model but ensure that flow estimates from each origin sum to the know totals 𝑂𝑂𝑖𝑖 rather than just the overall total. now at this point the 𝑂𝑂𝑖𝑖 and 𝐴𝐴𝑖𝑖 values could be calculated by hand for the sample system and the parameter values for the rest of the model could be guessed. however, the poisson regression framework allows this to be avoided. the production constrained model can be re-specified as a poisson regression model in exactly the same way as before. taking the logs of the right-hand side of the equation, and assuming that these are logarithmically linked to the poisson distributed mean (𝜆𝜆𝑖𝑖𝑖𝑖) of the 𝑇𝑇𝑖𝑖𝑖𝑖 variable, means that equation 7 becomes: 𝜆𝜆𝑖𝑖𝑖𝑖 = 𝑒𝑒𝑒𝑒𝑒𝑒(𝜇𝜇𝑖𝑖 + 𝛼𝛼ln𝑊𝑊𝑖𝑖 − 𝛽𝛽ln𝑑𝑑𝑖𝑖𝑖𝑖) (10) in equation 10 𝜇𝜇𝑖𝑖 is the equivalent of the vector of balancing factors 𝐴𝐴𝑖𝑖. but in regression/log-linear modelling terminology these can also be described as either ‘dummy variables’ or ‘fixed effects’. in practical terms what this means is that in the regression model 𝜇𝜇𝑖𝑖 is modelled as a categorical predictor3, and therefore in the poisson regression model the numeric values of 𝑂𝑂𝑖𝑖 are ignored and replaced by a categorical identifier for the origin. in terms of the origin/destination migration matrix shown in table 3, rather than the flow of 204,828 migrants leaving sydney (row 1) being used as a predictor, simply the code ‘1gsyd’ is used as a dummy variable. in the accompanying practical guide the code for running this model using the glm() function in r is provided. running the model will produce the following output (box 2). there are elements of the model output that should be familiar from the unconstrained model: • the α parameter related to the destination attractiveness (in this case, median weekly income): -0.27 is not much different from the unconstrained model. the z-score indicates that this is not a very important variable in explaining variation in migration behaviours in australia. • the β distance decay parameter: -1.23 has decreased meaning after controlling for origin characteristics, distance becomes more of a deterrent. where the model output differs is that the intercept (𝑘𝑘) parameter has been replaced by the vector of dummy variables/constraints 𝜇𝜇𝑖𝑖 relating to each origin. we can see from the standard outputs from the model that all of the explanatory variables are statistically significant (***); the z-scores indicate that the rest of queensland and greater sydney have greater emissivity properties than all other zones in the model, with factors associated with these zones more important in explaining migration patterns in australia than distance, which while still important, is less important than a number of origin zones. in the accompanying practical guide there is code that allows you to create a new set of estimates by both plugging these values back into a multiplicative model or by using a much easier built-in function in glm(). using either method will produce the set of flows shown in table 4. 3 https://en.wikipedia.org/wiki/categorical_variable https://en.wikipedia.org/wiki/categorical_variable https://en.wikipedia.org/wiki/categorical_variable https://rpubs.com/adam_dennett/376877 https://rpubs.com/adam_dennett/376877 https://en.wikipedia.org/wiki/categorical_variable australian population studies 2 (2) 2018 dennett 51 call: glm(formula = flow ~ orig_code + log(wj3_destmedinc) + log(dist) 1, family = poisson(link = "log"), data = mdatasub, na.action = na.exclude) deviance residuals: min 1q median 3q max -225.71 -54.10 -15.94 20.45 374.27 coefficients: estimate std. error z value pr(>|z|) orig_code1gsyd 19.541851 0.023767 822.22 <0.0000000000000002 *** orig_code1rnsw 19.425497 0.023913 812.35 <0.0000000000000002 *** orig_code2gmel 18.875763 0.023243 812.12 <0.0000000000000002 *** orig_code2rvic 18.335242 0.022996 797.31 <0.0000000000000002 *** orig_code3gbri 19.856564 0.024063 825.20 <0.0000000000000002 *** orig_code3rqld 20.094898 0.024300 826.94 <0.0000000000000002 *** orig_code4gade 18.747938 0.023966 782.28 <0.0000000000000002 *** orig_code4rsau 18.324029 0.024407 750.75 <0.0000000000000002 *** orig_code5gper 20.010551 0.024631 812.43 <0.0000000000000002 *** orig_code5rwau 19.392751 0.024611 787.96 <0.0000000000000002 *** orig_code6ghob 16.802016 0.024282 691.97 <0.0000000000000002 *** orig_code6rtas 17.013981 0.023587 721.33 <0.0000000000000002 *** orig_code7gdar 18.607483 0.025012 743.93 <0.0000000000000002 *** orig_code7rnte 17.798856 0.025704 692.45 <0.0000000000000002 *** orig_code8acte 17.796693 0.023895 744.79 <0.0000000000000002 *** log(wj3_destmedinc) -0.272640 0.003383 -80.59 <0.0000000000000002 *** log(dist) -1.227679 0.001400 -876.71 <0.0000000000000002 *** -- signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 (dispersion parameter for poisson family taken to be 1) null deviance: 23087017 on 210 degrees of freedom residual deviance: 1207394 on 193 degrees of freedom aic: 1209427 number of fisher scoring iterations: 6 box 2: outputs from the production constrained model specified in equation 10 comparing table 4 with table 3, it is very easy to see the origin constraints working. the sum across all destinations for each origin in the estimated matrix (table 4) is exactly the same (give or take the odd rounding error) as the same sum across the observed matrix (table 3): ∑ 𝑇𝑇𝑖𝑖𝑖𝑖𝑖𝑖 = ∑ 𝜆𝜆𝑖𝑖𝑖𝑖𝑖𝑖 = 𝑂𝑂𝑖𝑖. but clearly the same is not true when you sum across all origins for each destination: ∑ 𝑇𝑇𝑖𝑖𝑖𝑖𝑖𝑖 ≠ ∑ 𝜆𝜆𝑖𝑖𝑖𝑖𝑖𝑖 ≠ 𝐷𝐷𝑖𝑖. calculating the r2 value, the fit of the model has improved quite considerably: from around 0.32 in the unconstrained model to around 0.43 in this model. the rmse has also dropped quite noticeably. one of the advantages of singly constrained models is that once initial parameters have been calibrated on existing data, then changes can be made to destination variables (for origin/production constrained models) or origin variables (for destination/attraction constrained models) and the impact on flow estimates explored. for example, what would happen if average wages suddenly increased in an area? how would this impact migration flows to and from that area? the accompanying worked example demonstrates how this can be explored. https://rpubs.com/adam_dennett/376877 52 dennett australian population studies 2 (2) 2018 table 4: modelled flows from a production constrained spatial interaction model with parameters calibrated by a poisson regression model origin / destination 1gsyd 1rnsw 2gmel 2rvic 3gbri 3rqld 4gade 4rsau 5gper 5rwau 6ghob 6rtas 7gdar 7rnte 8acte (all) 1gsyd 0 36794 19752 18516 15905 8076 10591 7248 2504 2860 11192 11454 2519 4105 53308 204824 1rnsw 29163 0 18862 20620 13173 9548 13715 9329 2549 3032 8667 9100 2619 4543 26439 171359 2gmel 8501 10243 0 70950 3742 3243 10367 4685 1584 1705 11552 14147 1268 2109 14474 158570 2rvic 4924 6918 43838 0 2263 2050 7667 3139 961 1053 5309 6221 779 1320 7935 94377 3gbri 21684 22658 11852 11604 0 16555 9653 8526 3069 3722 8200 8144 3886 6207 14647 150407 3rqld 12057 17984 11248 11511 18128 0 12989 16188 4832 6746 7639 7664 8515 16335 10539 162375 4gade 4109 6714 9345 11186 2747 3376 0 9731 1895 2167 4506 4879 1403 2558 4912 69528 4rsau 1922 3122 2887 3130 1659 2876 6653 0 1438 2028 1780 1840 1264 2736 2017 35352 5gper 3930 5048 5777 5673 3533 5080 7666 8507 0 17470 4952 4882 4812 6954 4064 88348 5rwau 2445 3269 3387 3386 2333 3862 4775 6535 9514 0 2696 2679 4515 7196 2476 59068 6ghob 619 605 1485 1105 333 283 643 371 175 175 0 9840 129 201 807 16771 6rtas 827 829 2374 1689 431 371 908 501 225 226 12842 0 166 261 1121 22771 7gdar 1030 1350 1204 1198 1165 2331 1478 1948 1253 2159 950 937 0 6000 981 23984 7rnte 644 899 769 779 714 1716 1034 1618 695 1321 569 568 2303 0 618 14247 8acte 9622 6021 6070 5386 1939 1274 2285 1373 467 523 2631 2802 433 712 0 41538 (all) 101477 122454 138850 166733 68065 60641 90424 79699 31161 45187 83485 85157 34611 61237 144338 1313519 australian population studies 2 (2) 2018 dennett 53 2.2.3. the attraction constrained model the attraction constrained model is virtually the same as the production constrained model: 𝑇𝑇𝑖𝑖𝑖𝑖 = 𝐷𝐷𝑖𝑖𝐵𝐵𝑖𝑖𝑉𝑉𝑖𝑖 𝜇𝜇𝑑𝑑𝑖𝑖𝑖𝑖−𝛽𝛽 (11) where: 𝐷𝐷𝑖𝑖 = ∑ 𝑇𝑇𝑖𝑖𝑖𝑖𝑖𝑖 (12) and: 𝐵𝐵𝑖𝑖 = 1 ∑ 𝑉𝑉𝑖𝑖 𝜇𝜇 𝑖𝑖 𝑑𝑑𝑖𝑖𝑗𝑗 −𝛽𝛽 (13) the poisson model equation for the attraction constrained model would be: 𝜆𝜆𝑖𝑖𝑖𝑖 = 𝑒𝑒𝑒𝑒𝑒𝑒(𝜇𝜇ln𝑉𝑉𝑖𝑖 + 𝛼𝛼𝑖𝑖 − 𝛽𝛽ln𝑑𝑑𝑖𝑖𝑖𝑖) (14) its implementation in r is virtually identical to the production constrained model. see the accompanying walk-through exercise for full details of how to run these models with the sample dataset. because of the similarities to the production constrained model, the attraction constrained model will not be dwelt upon here. 2.2.3. the doubly constrained model the final model in the wilson (1971) family is the doubly constrained model. let’s begin with the formula: 𝑇𝑇𝑖𝑖𝑖𝑖 = 𝐴𝐴𝑖𝑖𝑂𝑂𝑖𝑖𝐵𝐵𝑖𝑖𝐷𝐷𝑖𝑖𝑑𝑑𝑖𝑖𝑖𝑖−𝛽𝛽 (15) where: 𝑂𝑂𝑖𝑖 = ∑ 𝑇𝑇𝑖𝑖𝑖𝑖𝑖𝑖 (16) 𝐷𝐷𝑖𝑖 = ∑ 𝑇𝑇𝑖𝑖𝑖𝑖𝑖𝑖 (17) and: 𝐴𝐴𝑖𝑖 = 1 ∑ 𝐵𝐵𝑗𝑗𝑗𝑗 𝐷𝐷𝑗𝑗𝑑𝑑𝑖𝑖𝑗𝑗 −𝛽𝛽 (19) 𝐵𝐵𝑖𝑖 = 1 ∑ 𝐴𝐴𝑖𝑖𝑖𝑖 𝑂𝑂𝑖𝑖𝑑𝑑𝑖𝑖𝑗𝑗 −𝛽𝛽 (20) astute readers will have noticed that the calculation of 𝐴𝐴𝑖𝑖 relies on knowing 𝐵𝐵𝑖𝑖 and the calculation of 𝐵𝐵𝑖𝑖 relies on knowing 𝐴𝐴𝑖𝑖 – something of a conundrum to which the solution is elegantly described by senior (1979), who sketches out a very useful algorithm for iteratively arriving at values for 𝐴𝐴𝑖𝑖 and 𝐵𝐵𝑖𝑖 by setting each to equal 1 initially and then continuing to calculate each in turn until the difference between successive iterations of the 𝐴𝐴𝑖𝑖 and 𝐵𝐵𝑖𝑖 values is small enough not to matter. in the accompanying practical guide an algorithm to achieve this using this multiplicative framework is provided. however, as you will have probably guessed by now, the poisson regression framework allows for the doubly constrained model to be fitted very easily. https://rpubs.com/adam_dennett/376877 https://rpubs.com/adam_dennett/376877 54 dennett australian population studies 2 (2) 2018 the poisson doubly constrained model takes the form: 𝜆𝜆𝑖𝑖𝑖𝑖 = 𝑒𝑒𝑒𝑒𝑒𝑒(𝜇𝜇𝑖𝑖 + 𝛼𝛼𝑖𝑖 − 𝛽𝛽ln𝑑𝑑𝑖𝑖𝑖𝑖) (21) when run in r and applied to the australian migration data we have been using, this model will produce the outputs shown in box 3. the coefficients in this version of the doubly constrained model will look a little different. this is explained in the accompanying walk-through exercise and is because an intercept has been added along with reference categories for the categorical variables, as two factor levels are used in this model. importantly the model estimates are not altered in any way by this. the reference level means that the origin and destination coefficients need to be interpreted in relation to a reference category. in this example, the first zone in the system is used (sydney), with the direction and size of the coefficients referring to whether another origin or destination zone has a greater or lesser positive or negative effect on migration flows in the system when compared to sydney. the estimates produced by the doubly constrained model are the most accurate in the wilson family of models (in this example, an r2 value of 0.87). however, there is a loss of flexibility when compared to the singly constrained models, as only alternatives to origin/destination interaction explanatory variables such as historic flows or something other than distance can be experimented with. the double constraints mean that originand destination-specific explanatory variables cannot be used. 2.2.4. further experimentation all of the way through this paper there has been an assumption that the distance decay parameter follows a negative power law. this does not have to be the case and empirically might not necessarily be so. in his original paper, wilson (1971) generalised the distance decay parameter to: 𝑓𝑓(𝑑𝑑𝑖𝑖𝑖𝑖) (22) where 𝑓𝑓 represents some function of distance describing the rate at which the flow interactions change as distance increases. lots of people have written about this, including taylor (1983) and more recently lovelace (2015) in a transport context. the inverse power law that has been used to this point is one possible function of distance; the other common one that is used is the negative exponential function: 𝑒𝑒𝑒𝑒𝑒𝑒(−𝛽𝛽𝑑𝑑𝑖𝑖𝑖𝑖) (23) the exact effect that the different function has on the rate of distance decay will depend on the value of 𝛽𝛽 as well as the function. however, figure 7 shows how the different functions and values of 𝛽𝛽 can combine to affect distance decay. https://rpubs.com/adam_dennett/376877 australian population studies 2 (2) 2018 dennett 55 call: glm(formula = flow ~ orig_code + dest_code + log(dist), family = poisson(link = "log"), data = mdatasub, na.action = na.exclude) deviance residuals: min 1q median 3q max -93.018 -26.703 0.021 19.046 184.179 coefficients: estimate std. error z value pr(>|z|) (intercept) 20.208178 0.011308 1786.999 <0.0000000000000002 *** orig_code1rnsw -0.122417 0.003463 -35.353 <0.0000000000000002 *** orig_code2gmel -0.455872 0.003741 -121.852 <0.0000000000000002 *** orig_code2rvic -1.434386 0.004511 -317.969 <0.0000000000000002 *** orig_code3gbri 0.241303 0.003597 67.091 <0.0000000000000002 *** orig_code3rqld 0.772753 0.003599 214.700 <0.0000000000000002 *** orig_code4gade -0.674261 0.004527 -148.936 <0.0000000000000002 *** orig_code4rsau -1.248974 0.005889 -212.091 <0.0000000000000002 *** orig_code5gper 0.742687 0.004668 159.118 <0.0000000000000002 *** orig_code5rwau -0.317806 0.005131 -61.943 <0.0000000000000002 *** orig_code6ghob -2.270736 0.008576 -264.767 <0.0000000000000002 *** orig_code6rtas -1.988784 0.007477 -265.981 <0.0000000000000002 *** orig_code7gdar -0.797620 0.007089 -112.513 <0.0000000000000002 *** orig_code7rnte -1.893522 0.008806 -215.022 <0.0000000000000002 *** orig_code8acte -1.921309 0.005511 -348.631 <0.0000000000000002 *** dest_code1rnsw 0.389478 0.003899 99.894 <0.0000000000000002 *** dest_code2gmel -0.007616 0.004244 -1.794 0.0727 . dest_code2rvic -0.781258 0.004654 -167.854 <0.0000000000000002 *** dest_code3gbri 0.795909 0.004037 197.178 <0.0000000000000002 *** dest_code3rqld 1.516186 0.003918 386.955 <0.0000000000000002 *** dest_code4gade -0.331189 0.005232 -63.304 <0.0000000000000002 *** dest_code4rsau -0.627202 0.006032 -103.980 <0.0000000000000002 *** dest_code5gper 1.390114 0.005022 276.811 <0.0000000000000002 *** dest_code5rwau 0.367314 0.005362 68.509 <0.0000000000000002 *** dest_code6ghob -1.685934 0.008478 -198.859 <0.0000000000000002 *** dest_code6rtas -1.454819 0.007612 -191.112 <0.0000000000000002 *** dest_code7gdar -0.308516 0.007716 -39.986 <0.0000000000000002 *** dest_code7rnte -1.462020 0.009743 -150.060 <0.0000000000000002 *** dest_code8acte -1.506283 0.005709 -263.866 <0.0000000000000002 *** log(dist) -1.589102 0.001685 -942.842 <0.0000000000000002 *** -- signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 (dispersion parameter for poisson family taken to be 1) null deviance: 2750417 on 209 degrees of freedom residual deviance: 335759 on 180 degrees of freedom aic: 337818 number of fisher scoring iterations: 6 box 3: outputs from the doubly constrained model specified in equation 21 56 dennett australian population studies 2 (2) 2018 figure 7: alternative distance decay curves for alternative values of 𝜷𝜷 and different functions in this particular example with these parameters and 𝛽𝛽 values, the inverse power function has a far more rapid distance decay effect than the negative exponential function. in real life, what this means is that if the observed interactions drop off very rapidly with distance, then they might be more likely to follow an inverse power law. this might be the case when looking at trips to the local convenience store by walking, for example. on the other hand, if the effect of distance is less severe – for example, migration across the country for a new job – then the negative exponential function with a small value of 𝛽𝛽 function might be more appropriate. there is no hard and fast rule as to which function to pick. it will just come down to which fits the data better. following oshan’s (2016) example, the accompanying walk-through exercise will allow you to explore the effect on model fits and predictions of fitting different distance decay functions to the distance variable. the final point to note is that the regression modelling framework means that adding additional explanatory variables into the spatial interaction model is very easy compared with the multiplicative framework. in the accompanying walk-through guide, in addition to variables relating to median income, there are variables on unemployment rate and the percentage of households living in rented accommodation. experiment with these variables for origins and destinations to see whether the singly constrained models can be improved in any way. 3. conclusions spatial interaction modelling is one of the key tools in the population geographer’s tool kit, but for too long has been inaccessible to researchers new to the field or without computer programming expertise. recent advances in more forgiving software environments like r and python now mean that with much less (although admittedly still some) effort, this powerful modelling tool can be accessed by more people. this guide has been designed to introduce researchers to spatial interaction modelling in, hopefully, an accessible way through exemplification of two modelling frameworks – the wilson-esque multiplicative framework and the poisson regression additive modelling framework – and an accompanying walk-through guide. https://rpubs.com/adam_dennett/376877 http://rpubs.com/adam_dennett/376877 http://rpubs.com/adam_dennett/376877 australian population studies 2 (2) 2018 dennett 57 acknowledgements thanks to hadrien salat in casa who helped with some 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statistical society. series a, statistics in society 170(4): 891–908. raymer j and giulietti c (2010) analysing structures of interregional migration in england. in: stillwell j, duke-williams o and dennett a (eds) technologies for migration and commuting analysis: spatial interaction data applications. hershey pa: igi global. rees p (1977) the measurement of migration from census data and other sources. environment and planning a: economy and space 9(3): 257–280. rogers a and raymer j (1998) the spatial focus of us interstate migration flows. population, space and place 4(1): 63–80. senior m l (1979) from gravity modelling to entropy maximizing: a pedagogic guide. progress in human geography 3(2): 175–210. shen j (2017) modelling interregional migration in china in 2005–2010: the roles of regional attributes and spatial interaction effects in modelling error. population, space and place 23(3): e2014. shen j (2015) explaining interregional migration changes in china, 1985–2000, using a decomposition approach. regional studies 49(7): 1176–1192. stillwell j (1978) interzonal migration: some historical tests of spatial-interaction models. environment and planning a: economy and space 10(1): 1187–1200. taylor p j (1983) distance decay in spatial interactions. norwich: geo books. willekens f (1999) modeling approaches to the indirect estimation of migration flows: from entropy to em. mathematical population studies 7(3): 239–278. wilson a (1971) a family of spatial interaction models, and associated developments. environment and planning a: economy and space 3(1): 1–32. zipf g k (1946) the p1 p2 / d hypothesis: on the intercity movement of persons. american sociological review 11(6): 677–686. australian population studies 2019 | volume 3 | issue 2 | pages 34-36 © lazzari 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org socio-economic changes in the age-patterns of childbearing in australia ester lazzari* australian national university * corresponding author. email ester.lazzari@anu.edu.au. address: school of demography, anu college of arts and social sciences, the australian national university, 9 fellows road, acton, act 2601, australia paper received 1 august 2019; accepted 17 october 2019; published 18 november 2019 over the past three decades the median age of mothers in australia has continued to rise, although age-patterns of childbearing vary widely between poorer and wealthier areas. using data on the number of children ever born to women aged 15 years and over sourced from the 2006 and 2016 censuses, this demographic examines changes in the timing and quantum of childbearing of australian mothers across different socio-economic statuses. in developed countries, fertility has been progressively decreasing at younger ages and increasing at older ages, a phenomenon known as postponement (kohler et al. 2002). despite the overall shift towards later childbearing, significant variation in the median age of mothers can be found across different socio-economic groups. there is a vast literature showing that the trend towards postponed childbearing primarily occurs among women with high educational attainment (heck et al. 1997). not only are highly educated women likely to start their families later because of their pursuit of education and career (kaizer et al. 2007), but they also tend to have fewer children due to the natural decline in fertility with age (steiner and jukic 2016). the 2016 census was used to quantify the number of babies ever born to women aged 15 years and over by the statistical areal level 2 (sa2) of usual residence, as defined by the australian statistical geography standard (asgs) of the abs. to analyse whether socio-economic circumstances have an effect on the timing of childbearing, i used the index of relative socio-economic advantage and disadvantage (irsad) developed by the abs, which ranks areas in australia according to a set of variables including relative educational and occupational level (abs 2018). the index is used to group the population into five socio-economic statuses: ses1 (most disadvantaged), ses2, ses3, ses4, and ses5 (most advantaged). the index is based on census data and assigns summary values of socioeconomic conditions to each geographic area. between 2006 and 2016, the average age of all women who gave birth increased from 29.8 to 30.5 years old (aihw 2016). figure 1 displays the changes over the ten year intercensal period in the proportion of women with one, two and three children by age and socio-economic status (ses) as defined by the 2016 irsad index values. despite a general increase in the median age of australian mothers across parities, a variation by socio-economic status can be observed, with mothers from wealthier areas experiencing substantially later ages at first, second and third birth compared to d em og ra ph ic http://www.australianpopulationstudies.org/ mailto:ester.lazzari@anu.edu.au australian population studies 3 (2) 2019 lazzari 35 figure 1: cumulative difference in the proportion of children ever born between 2006 and 2016 by socioeconomic status and parity source: calculated by the author using data extracted from the 2006 and 2016 censuses using tablebuilder women from poorer areas. at the ses5 level, the gap in the proportion of first-time mothers between 2006 and 2016 was at its greatest at the age of 26 (9.3 per cent). a recuperation trend can be observed after age 26, with the proportion of mothers slightly increasing until age 36, when 4.5 per cent more women were first-time mothers than in 2006. similar patterns can be observed at parity 2 and 3, even though recuperation at parity 3 is rather modest and the proportion of third-time mothers never surpasses that of 2006. by contrast, at the ses1 level, the peak of first-time births was reached at the age of 22 at parity 1, 25 at parity 2 and 30 at parity 3, showing an anticipation rather than a postponement in childbearing compared to the benchmark year. 36 lazzari australian population studies 3 (2) 2019 socio-economic circumstances seem to have different impacts on the probability of entry into motherhood in different periods of life. the trend of childbearing postponement differs across socioeconomic groups and the increase in the age at birth of australian mothers is driven by women with high socio-economic status. low socio-economic status was associated with entry into motherhood at younger ages, while high socio-economic status was associated with childbearing postponement and increased fertility at older ages. interestingly, fertility was lower among the most disadvantaged groups, suggesting that socio-economic circumstances affect both timing and quantum of fertility. by the end of the reproductive years, there were 2.5 per cent more first-time mothers and 9.2 more second-time mothers in the ses5 than in the ses1, while only a slightly higher proportion of women in the ses1 gave birth to a third child by the age of 49 (1.8 per cent). the decrease in the total fertility rate from 1.87 in 2006 to 1.79 in 2016 (abs 2017) seems to be driven by women with low socioeconomic status, which despite having their first child relatively young, have fewer children overall than women in higher ses groups. family policies tend to mainly favour working women and, hence, it has been argued that women in higher socio-economic statuses account for these observed fertility patterns (mcdonald and moyle 2019). references abs (2017) births, australia, 2016. catalogue no. 3301.0. canberra: abs. abs (2018) census of population and housing: socio-economic indexes for areas (seifa), australia, 2016. catalogue no. 2033.0.55.001. canberra: abs. australian institute of health and welfare (2019) australia’s mothers and babies 2017 in brief. perinatal statistics series 35. canberra: aihw. heck k, schoendorf k c, ventura s j and kiely j (1997) delayed childbearing by education level in the united states, 1969–1994. maternal and child health journal 1 (2): 81-88. kaizer r, dykstra p a and jansen m d (2007) pathways into childlessness: evidence of gendered life course dynamics. journal of biosocial science 40 (6): 863-878. kohler h-p, billari f c and ortega j a (2002) the emergence of lowest-low fertility in europe during the 1990s. population and development review 28(4): 641-680. mcdonald p and moyle h (2019) in australia fertility is falling only for low educated women. n-iussp. http://www.niussp.org/article/in-australia-fertility-is-falling-only-for-low-educated-womenenaustralie-la-fecondite-baisse-uniquement-chez-les-femmes-peu-scolarisees/. accessed on 4 july 2019. steiner a z and jukic a m z (2016) impact of female age and nulligravidity on fecundity in older reproductive age cohort. fertility and sterility 105(6): 1584-1588. http://www.niussp.org/article/in-australia-fertility-is-falling-only-for-low-educated-womenen-australie-la-fecondite-baisse-uniquement-chez-les-femmes-peu-scolarisees/ http://www.niussp.org/article/in-australia-fertility-is-falling-only-for-low-educated-womenen-australie-la-fecondite-baisse-uniquement-chez-les-femmes-peu-scolarisees/ australian population studies 2021 | volume 5 | issue 1 | pages 3-8 © charles-edwards 2021. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org commentary living in more than one place: capturing dual-local lives in the 2026 census elin charles-edwards the university of queensland email: e.charles-edwards@uq.edu.au. address: queensland centre for population research, school of earth and environmental sciences, the university of queensland, brisbane, australia 4072. paper received 5 march 2021; accepted 20 april 2021; published 31 may 2021 1. introduction the concept of “usual residence” is central to the collection of population data in the australian census of population and housing and the basis of australia’s official population statistic, the estimated resident population. usual residence is defined in the census as “...the address at which a person lives or intends to live for six months or more” (abs 2017). growth in spatial mobility and a “pluralisation” of living arrangements makes that the notion of a single usual residence problematic for a growing share of the population (schier et al. 2015). this includes second (vacation) homeowners (atkinson et al. 2009), long-distance commuters (including fly-in fly-out workers), children living in shared custody arrangements (stjernström and strömgren 2012), and couples “living apart together” (reimondos, evans, and gray 2011). few data sources capture these populations in australia, and available data lack detailed socioeconomic attributes and reliable spatial information which are critical for policy and planning. there are myriad applications of such data, ranging from the development of service population estimates (mckenzie, martin, and paris 2008) and emergency preparedness, to better understanding of residential multi-locality (schier 2016) and regional population dynamics (adamiak et al. 2017). there are longstanding calls for the inclusion of a census question on dual or second residence (abs 2007). a question on second residence was researched and tested for 2016 but not selected as it was “…difficult for respondents to understand” (abs 2018) as well as having a significant cost impost. despite renewed calls for inclusion in the 2021 census, a question on second residence was again rejected. public submissions for the 2021 census also called for information on children living in multiple residences as part of shared care arrangements (abs 2018), a form of dual-local living, but was not selected for inclusion. while there are certainly barriers to the inclusion of questions on dual residence including respondent burden, recall issues and cost, calls for better information on dual-local individuals and households are likely to persist and grow over time. http://www.australianpopulationstudies.org/ mailto:e.charles-edwards@uq.edu.au 4 charles-edwards australian population studies 5 (1) 2021 2. proposed census questions given the reticence of the abs to include a question on dual residence in the census, it is illustrative to turn to other jurisdictions. second or dual residence data can be collected directly via a targeted census question or indirectly as a by-product of the census enumeration strategy. the england and wales censuses have included questions on dual residence since 2011. respondents are first asked, “do you stay at another address for more than 30 days a year?”. if respondents answered “yes” they were prompted to enter the full uk residential address or the country if the second residence was abroad. this was followed by a question asking respondents to nominate the type of residence from the following options: armed forces base address; another address when working away from home; student’s home address; student’s term-time address; another parent or guardian’s address; holiday home; other. the question has been retained for the 2021 census with only the addition of “partner’s house” as a response for the type of residence. the formulation used by the england and wales censuses allows the identification of a range of dual-local arrangements including second homes, long-distance commuting, couples living apart together and children in shared custody arrangements. a question on dual residence was included in the 2001 italian census. respondents were asked to “indicate whether during the past 12 months (21 october 2000 21 october 2001) the person lived in accommodation or institutional household (e.g., relatives or friends house, barracks, hospital) other than the present”. respondents were then asked to nominate the number of days from a closed-response set. persons living at another address for more than 90 days were asked to indicate if the person was currently absent, followed by the location of the accommodation (in this municipality; in another municipality; and abroad). a final question asked the reasons for absence. pre-coded responses included: work; study; vacation; presence of relatives; vacation; previous usual residence; other. the formulation used in the 2001 italian census produced data on dual-local living arrangements tied to work, study, family and leisure. this question was not retained in the 2011 italian census. the 2020 united states census collected information on second homes (indirectly) as a by-product of its enumeration strategy. individuals were directed to complete the census at their primary residence; however, homeowners were asked to complete a form for all properties owned and had the option of nominating these properties as seasonal homes. us census data on second homes are available back to the 1940s but are limited to the number and distribution of second homes across us states (us census bureau 2017). information on the utilisation of seasonal homes, including the duration and purpose of use, is not available. following the example of the england and wales census and the 2011 italian census, the following suite of questions is proposed for the 2026 census in australia (figure 1). the proposed questions follow the same format as the england and wales censuses. this is due to their simplicity and low respondent burden compared with the italian formulation. an indirect data item, such as collected in the us, is rejected due to its inability to enumerate dual-local households, such as couples living apart together and fly-in fly-out arrangements. it is proposed that the 30-day threshold is replaced by the term “regularly” to reduce recall burden for respondents. supplementary information is, however, required to provide respondents with the definition of “regular”, here proposed as australian population studies 5 (1) 2021 charles-edwards 5 “recurring at uniform or fixed intervals e.g., weekly, monthly or seasonally”. respondents regularly living at more than two addresses should be instructed to select only one. the response set for question 2 is shorter than the england and wales equivalent, and aims to capture the main forms of dual residence living in australia including long distance commuting, children in shared custody, couples living apart together and second homeowners. [1] in the past year, have you regularly stayed at another address? [ ] no [ ] yes, write in other australian address below (address write-in) or [ ] yes, outside australia , write in country [2] what is that address? [ ] another address when working away from home [ ] parent or guardian's address [ ] a partner’s address [ ] holiday home [ ] other figure 1: proposed census questions on dual residence source: author 3. discussion census statistics on dual residence have several potential applications. in this section, three are described alongside a brief discussion of past research and existing data sources. these are: understanding the impacts of second home communities; the intensity, pattern and composition of long-distance commuting (ldc); and the distribution and characteristics of couples living apart together (lat). second or vacation homes are a significant feature of regional landscapes in australia and overseas. while there is extensive literature on second homes, the vast majority of papers are focused on europe and north america. this literature points to the varied social (gallent 2014), economic (hilber and schöni 2020; velvin et al. 2013) and environmental (hiltunen 2007; næss et al. 2019) impacts of second homes. besides improving our understanding of these varied impacts, accurate statistics on second homes would be useful for planning and provision of goods and services and emergency preparedness as part of service population estimates (mckenzie, martin, and paris 2008; charlesedwards, bell, and brown 2008). several australian sources provide partial insight into the number and distribution of second homes in australia, including census counts of unoccupied dwellings, the national visitor survey (nvs), and the household, income and labour dynamics in australia (hilda) survey. at the 2016 census, 11 per cent of private dwellings were unoccupied, up from 10 per cent in 2011. over fifty per cent of private dwellings were unoccupied on census night in the local government areas of central highlands, robe, queenscliffe, tasman, dandaraga, and glamorgan/spring bay (table 1). 6 charles-edwards australian population studies 5 (1) 2021 table 1: percentage of unoccupied private dwellings, selected local government areas, 2016 census local government area state % unoccupied private dwelling central highlands tasmania 61 robe south australia 58 queenscliffe victoria 54 tasma tasmania 52 dandaragan western australia 51 glamorgan/spring bay tasmania 50 source: abs tablebuilder, 2016 census this statistic includes homes for sale, new homes yet to be occupied, homes in which the residents were absent on census night as well as second homes. no information on individuals using second homes is collected and thus the utility of census data is limited to identifying (potential) second home locations. data have, however, been used for this purpose to good effect (see e.g., frost 2004). the nvs collects data on trips and visitors to second homes (recorded as “own property”) by australians aged 15 years and over and includes information on trip activities as well as limited demographic data. in 2019, the nvs recorded almost 5 million overnight trips to second homes of a total of 117 million overnight trips (tourism research australia 2021). sampling variability is large at the local area level which limits the utility of these data for understanding second home impacts. hilda collects data on second home ownership, along with a rich array of sociodemographic data, but does not collect any information on the location of second homes, again limiting their utility for studying impacts at the local area level. the proposed census questions on dual residence overcome the main shortcomings of the extant data sets providing reliable information on both the spatial distribution of second homes at the small area level as well as detailed information on the attributes of individuals visiting them. fly-in fly-out (fifo) and drive-in drive-out (dido) arrangements in the mining and construction sectors has disrupted the traditional relationship between place of usual residence and place of work in many parts of australia (see the article by haslam mckenzie in this issue). fifo arrangements are just one form of long-distance commuting (ldc), an arrangement whereby people live beyond daily commuting distance from their workplace, necessitating several nights stay near their place of work before returning “home”. several studies have attempted to estimate the intensity (kpmg for the minerals council of australia 2013), geography (nicholas and welters 2016), and characteristics (de silva, johnson, and wade 2011) of ldc by cross-classifying a combination of census data on place of usual residence, place of enumeration and place of work and then applying some distance threshold that precludes daily commuting. estimates of the extent of ldc vary depending on the classification method and distance thresholds used (nicholas and welters 2016). more accurate data on ldc is important to understand the social and economic impacts of ldc on individuals, families and communities. this may become increasingly important in the post-covid-19 era with increased acceptance of working from home potentially facilitating more ldc arrangements. a final application of the proposed question on dual residences relates to our understanding of couples living apart together (lat). in recent decades, lat has emerged as an important new household form, with estimates suggesting it involves around 10 per cent of the adult population in australian population studies 5 (1) 2021 charles-edwards 7 western europe, north america and australasia (duncan et al. 2014). relatively little research on lat has been undertaken in australia (for exceptions see tai et al. 2014 and reimondos et al. 2011). research from overseas suggests that the prevalence of these relationships is likely to increase over time, particularly among older adults (benson and coleman 2016). growth in lat relationships has the potential to impact average household size and dwelling demand (reuschke 2010), as well as residential mobility (wagner and mulder 2015). while there are some survey data on lat in australia (e.g., hilda), little remains known about the geographic distribution of these relationship and their impacts on urban form and spatial mobility. the three applications described above highlight the growing complexity of living arrangements in australia as well as the sustained efforts of researchers and policymakers to understand the intensity, composition and geography of dual-local arrangements and their impacts. the increase in dual-local individuals presents a challenge to traditional population statistics which are founded on the notion of a single place of usual residence. the growth in personal mobility, improvements in telecommunication technology and continued dismantling of traditional societal norms has the potential to increase the prevalence of such arrangements. statistics on dual resident individuals and households are therefore likely to become more important over time. references abs (2007) 2007.0 information paper: census of 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https://www.tra.gov.au/tra-online/tra-online https://www.census.gov/data/tables/time-series/dec/coh-vacation.html https://doi.org/10.5367/te.2013.0216 http://doi.org/10.1007/s11577-015-0327-4 http://doi.org/10.1007/s11577-015-0327-4 australian population studies 2019 | volume 3 | issue 1 | pages 40-56 © wilson 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org introductory guide an introduction to population projections for australia tom wilson* charles darwin university * email: tom.wilson@cdu.edu.au. address: northern institute, charles darwin university, darwin, nt 0909 paper received 30 january 2019; accepted 19 april 2019; published 27 may 2019 abstract background population projections for australia are produced by many organisations. they differ in projected population numbers, methods used, level of output detail, temporal extent, frequency of revision, quality and purpose, and they are not always easy to find. aims this paper provides a brief guide to many of the population projections prepared for australia in recent years. it gives an overview of projection methods and selected results, a brief commentary on key aspects of the projections, and shows readers where to find more data and information. data and methods projections data were obtained from the various organisations producing projections. they are presented in order of spatial detail: national scale, states and territories; large sub-state regions; and then local and small areas. results the abs and state and territory governments are the main producers of population projections and forecasts in australia, and generally these projections are good quality. they cover a wide variety of spatial scales from the national level to local areas, such as sa2s. a great deal of projections data and information is now freely available online. conclusions population projections and forecasts can be very useful data for a wide variety of planning, policy and research purposes. but it is important to be aware of their limitations. key words population projections; population forecasts; projections data; australia http://www.australianpopulationstudies.org/ mailto:tom.wilson@cdu.edu.au australian population studies 3 (1) 2019 wilson 41 1. introduction population projections are calculations of population beyond the latest population estimate based on assumptions about the future of fertility, mortality and migration. projected populations, and sometimes also projected births, deaths and migration, are used in a wide variety of planning, policy development, service delivery, market assessment, and research activities, as well as in public debates about australia’s future. for example:  state and territory governments formulate urban and regional plans which take into account the future demand for housing, schools, hospitals, public transport, and so on;  utility companies wish to plan for future electricity, water and sewage treatment needs;  the commonwealth government uses projections to assess the likely costs of future health provision and aged pensions (as shown in its intergenerational reports, e.g. australian treasury 2015);  the australian electoral commission uses short-term projections of enrolments to vote to adjust electoral boundaries to ensure constituencies are likely to contain roughly equal numbers of electors (e.g. australian electoral commission 2017). projections are also sometimes used as interim population estimates for the present because official estimated resident populations (erps) are published some time after their reference dates (between around 6 and 15 months depending on geographical scale and level of demographic detail). population projections for australia are produced by many organisations. they differ in projected population numbers, methods used, level of output detail, temporal extent, frequency of revision, quality, and purpose. and they are not always easy to find on the web. the aim of this paper is to provide a brief guide to many of the population projections prepared for australia in recent years. it gives an overview of methods employed, data outputs, where projections data and accompanying information can be obtained, along with a few comments about the projections. national projections are covered first, followed by those for states and territories, major sub-state regions, and then local and small areas. details of the projections are not presented and interested readers are encouraged to look up the web resources listed in the paper to find out more. projections of other demographic variables, such as households, living arrangements, dwellings, populations by indigenous status, school enrolments and so on, are outside the scope of the paper. be aware that all projections mentioned in the paper (along with urls) refer to those publically available as of 30th april 2019. projections are revised regularly and may have been updated since the time this article was finalised. before proceeding any further i define the meanings of some common projections terms such as projection horizon, jump-off year, and the difference between a projection and a forecast. these are listed in box 1. 42 wilson australian population studies 3 (1) 2019 box 1: projections terminology jump-off year: the starting year of population projections; the year in which they ‘jump off’ into the demographic future. it is sometimes also known as the launch year. population estimate: the population for a past or current point in time derived from demographic information available for that time. population projection: a calculation of population beyond the jump-off year based on certain assumptions about the future of fertility, mortality and migration (and sometimes other variables). projection series: a projection with a specified combination of fertility, mortality and migration assumptions (often labelled low, medium, or high; or sometimes labelled with letters and numbers). projection scenario: a projection based on a vision, story, or set of particular circumstances (e.g. restrictive immigration policy scenario; major new employer scenario; mine closure scenario). population forecast: a population projection deemed to be the most likely future population; a prediction. (therefore all forecasts are projections, but many projections are not forecasts). projection/forecast horizon: the time period between the jump-off year and the final year of the projections/forecasts. projection assumptions: data inputs to the projection calculations which usually include the assumed future of fertility, mortality, and migration (and sometimes other input variables, e.g. housing developments). if more broadly defined, projection assumptions also implicitly or explicitly include qualitative elements, such as expectations about future immigration policy, and the absence of major disasters. probabilistic projections/forecasts: projections/forecasts which are expressed as a range of future populations, often with prediction intervals. prediction intervals consist of a range with a probability of future population lying within that range. deterministic projections/forecasts: projections/forecasts which are expressed as a single set of values; most national projections and almost all subnational projections are of this type. net migration: the value of inward migration minus outward migration, such as net interstate migration (nim) which is interstate in-migration minus interstate out-migration, or net overseas migration (nom) which is immigration (which the australian bureau of statistics (abs) terms nom arrivals) minus emigration (nom departures). directional migration: flows of migration from one country or region to another; for example, migration from overseas to australia (immigration), or from new south wales to other jurisdictions within australia (interstate out-migration). source: the author australian population studies 3 (1) 2019 wilson 43 2. population projections for australia 2.1. national population projections the best known population projections for australia are those produced by the australian bureau of statistics (abs) in their population projections, australia publication. updated every five years, the most recent abs projections were released in november 2018 (abs 2018a). these projections start from a jump-off year of 2017 and cover a projection horizon of almost 50 years, ending in 2066. the abs applies a standard cohort-component model1 incorporating directional migration flows (immigration and emigration) constrained to total net overseas migration (nom) assumptions (abs 1999). most emphasis is placed on three main projection series – a, b and c – which are often interpreted as high, medium and low series. a further 69 projection series with differing fertility, mortality and migration assumptions are also prepared and are available for download from the abs website. series b is generally interpreted by users to be a forecast, though abs deliberately avoids the term ‘forecast’ and emphasises that all its future population numbers are merely projections. the series b projection sees australia’s population increasing from 24.6 million in 2017 to 42.6 million by 2066, the result of a long-run total fertility rate of 1.80, net overseas migration of 225,000 per annum, and modest and decelerating increases in life expectancy at birth (86.0 years for females and 83.0 years for males by the end of the projection horizon). the projected population growth rate gradually declines into the future because population ageing results in the number of deaths rising slightly faster than births, and because a fixed level of net overseas migration in the context of an increasing population represents a falling crude rate of net migration. the projection assumptions are based primarily on recent levels of fertility and net overseas migration observed over the last few years, and the small increases in life expectancy observed in recent years. these trends are assumed to continue. interestingly, life expectancy at birth is expected to rise by very little and is less optimistic than in the previous set of abs projections (abs 2013), and by the 2060s is over 2 years of life lower. some users may wish to download projection series 26 which incorporates the abs high life expectancy assumptions (increasing to 87.7 years and 89.2 years for males and females respectively by 2065-66). the series 26 projection is 1.1 million higher than series b by 2066, nearly all of which is in the 65+ age group. figure 1 illustrates the latest abs series b projection alongside several others for australia, while figure 2 presents some of the assumptions on which those projections were based. box 2 includes urls which will take readers to these and other projections mentioned in the paper. the united nations population division updates population projections for australia every two years as part of its world population prospects publication (un 2017a). this publication contains projections for all countries of the world (except the very smallest) along with projections for the world as a whole. the projections in the 2017 revision of world population prospects start from a jump-off year of 2015 and extend all the way out to 2100. the un uses a cohort-component model with five year age groups which proceeds forward in five year intervals; overseas migration is generally projected as net migration numbers due to the lack of reliable data on immigration and 1 for basic introductions to the cohort-component model see rowland (2003) chapter 12, or smith et al. (2013) chapters 3 to 7. for a description of subnational and multiregional cohort-component models see rees (1997) and the review in rees et al. (2015). 44 wilson australian population studies 3 (1) 2019 emigration flows for all countries (un 2017b). the demographic transition model (dyson 2010) provides the over-arching theoretical framework for setting fertility and mortality assumptions, so that all countries are assumed to progress through the transition from high to low fertility and mortality rates. net overseas migration is assumed to remain constant until 2045-50 if recent numbers have been stable, and then decline to half that number by 2095-2100. this approach was taken because it “represents a compromise between the difficulty of predicting the levels of immigration or emigration for each country of the world over such a far horizon, and the recognition that net migration is unlikely to reach zero in individual countries” (un 2017b p. 30). the un’s projection assumptions for australia consist of a long-run tfr varying slightly between 1.76 and 1.80, life expectancy reaching 87.3 years for males and 90.5 years for females by 2060-65 (and 91.5 and 94.7 years respectively by 2095-2100), and net overseas migration set to an annual average of 150,000 from 2020 to 2050, declining gradually to 75,000 by 2095-2100. the un assumptions for mortality and migration differ considerably from those of the abs series b projection, with the un selecting much higher life expectancy and much lower net overseas migration levels. according to the un’s main series projection, australia’s population is projected to increase from 23.8 million in 2015 to 41.8 million by 2100. by 2066 it is expected pass 36.6 million (7 million lower than the abs series b projection). differences with abs projections are largely due to nom assumptions and are particularly noticeable in the 0-14 and 15-64 age groups (figure 1b). the un projections comprise nine variants as well as probabilistic projections created from probabilistic fertility and mortality inputs (though, interestingly, not probabilistic overseas migration inputs). outputs from, and information about, these alternative projections can be found at the webpage listed in box 2. intergenerational reports are prepared by the australian treasury every few years, with the most recent being the 2015 report (australian treasury 2015). the purpose of these reports is to “assess the long-term sustainability of current government policies and how changes to australia’s population size and age profile may impact economic growth, workforce and public finances” (australian treasury 2015 p. xxiii). the assessment is underpinned by a series of demographic and economic projections looking ahead over the next four decades. the population projections are prepared with a standard cohort-component model. treasury’s projection for australia’s population in 2055 is 39.7 million, the result of a total fertility rate of 1.90, life expectancy at birth increasing to 87.5 years for males and 90.1 years for females by 2050, and long-run net overseas migration levels of 215,000 per annum. population projections for australia are also produced by other organisations and individuals as occasional or one-off exercises. three examples are mentioned here. the productivity commission created population projections as part of the report an ageing australia (productivity commission 2013). their projections from 2012 to 2060 put the national population at 38.3 million by the end of the projection horizon. lutz et al. (2018) created projections for most countries of the world by educational status from 2015 to 2100. their medium scenario has australia’s total population at 32.5 million by 2050 and 43.6 million by 2100. bell et al. (2011) prepared probabilistic population forecasts for australia from 2010 to 2051. their forecasts included a 95% prediction interval for australia’s total population in 2051 spanning 29.4 to 43.0 million, with the median of the distribution at 36.1 million. australian population studies 3 (1) 2019 wilson 45 (a) projections of australia’s total population (b) projections of australia’s population aged 0-14, 15-64 and 65 years and over figure 1: some recent projections of australia’s population notes: erp = estimated resident population sources: abs (2018a; 2018b), un (2017a), australian treasury (2015) 46 wilson australian population studies 3 (1) 2019 (a) net overseas migration assumptions (b) life expectancy at birth assumptions (c) total fertility rate assumptions figure 2: assumptions behind some recent projections of australia’s population notes: tfr = total fertility rate; e0 = life expectancy at birth sources: abs (2014; 2018a; 2018b), human mortality database (2017), un (2017a), australian treasury (2015) australian population studies 3 (1) 2019 wilson 47 2.2. projections at the state and territory scale the abs and state and territory governments all produce population projections at the state and territory scale every few years. abs state and territory projections are published as part of its population projections, australia publication (abs 2018a). these projections have a high profile because they are published by the national statistical office. because they are produced using a consistent method, and have net interstate migration summing to the logical value of zero across all jurisdictions, the projections are useful for analyses involving all states and territories across australia. state and territory governments produce projections for their own state/territory as a whole, plus projections for a variety of sub-state geographies, with updates mostly prepared every 2 to 5 years. these projections are important because government departments within that state or territory are required to use them in their analysis, planning and budgeting. data and information on all these projections can be obtained from the urls listed in box 2. the abs projects state and territory populations with a cohort-component model which is similar to the national-scale model but with the addition of interstate migration. interstate inand outmigration flows are handled as directional (rather than net) migration flows but are constrained to be consistent with assumed net interstate migration (nim) totals. the model is not a fully multiregional model with flows between each state/territory and every other, but a bi-regional type which handles inand out-migration flows between each state/territory and the remainder of the country (abs 1999; wilson and bell 2004). in the latest set of abs projections medium variant nim assumptions are based on the average nim values of the last 10 years. series b state and territory population projections are illustrated in figure 3 alongside those produced by state and territory governments. a log scale is used in the graph to clearly show the projected trends of the less populous states and territories. all state and territory governments make use of cohort-component projection models of various types. most projection models use directional (rather than net) migration, which is conceptually better and avoids implausible outputs. some models work with five year age groups and projection intervals, though most use single year ages and intervals; some state and territory governments produce only one set of projections while others produce multiple series. medium series projections often use assumptions which deliver similar results to the abs series b projections in terms of total population, which is probably a mix of similar thinking and a desire to avoid having to explain to users why their projections are so different. the new south wales department of planning and environment produces official nsw government population projections for nsw. high, medium and low series are produced. the latest projection covers a horizon of 2011 to 2041 and the medium series puts the nsw population at 10.46 million by the end of that period (nsw department of planning and environment 2016). these projections are fractionally lower than those of the abs. the department of environment, land, water and planning in victoria produces population projections for its victoria in future publication. only one projection series is published. the latest ‘victoria in future 2016’ projections cover the period 2011 to 2051 at the state level and show victoria’s population increasing from 5.54 million to 10.09 million over those four decades (victorian 48 wilson australian population studies 3 (1) 2019 department of environment, land, water and planning 2016). these are a little lower than the abs series b projections. the queensland government statistician’s office prepares the official population projections for that state. high, medium and low series are published. its latest projections were published in 2018 and extend from 2016 to 2066. the medium series projections indicate growth from 4.85 million to 9.51 million over the projection horizon (queensland government statistician’s office 2018), showing marginally higher growth than the abs series b projection. western australia tomorrow is the publication produced by the department of planning, lands and heritage containing population forecasts for western australia (western australian planning commission 2018). these projections are unusual in that they are formally labelled ‘forecasts’ and are produced by a form of probabilistic cohort-component model. within the probabilistic forecasts five alternative projection trajectories are distinguished, labelled bands a, b, c, d and e. the latest band c (medium series) forecasts envision wa’s population growing from 2.35 million in 2011 to 3.25 million by the end of the projection horizon in 2031 (western australian planning commission 2018), which is slightly higher than abs series b projection. tasmania’s latest population projections were published recently and include high, medium and low series. the medium series show the state’s population growing from 522,000 in 2017 to 577,000 by 2067 (tasmanian department of treasury and finance 2019). the projected trajectory of tasmania’s total population is close to the latest abs series b projection. the northern territory’s projected population is calculated as the sum of separate projections for its indigenous and non-indigenous residents, a feature which is unique amongst the state and territory government population models. the cohort-component model incorporates overseas and interstate migration flows, permits changes to reported indigenous status over time, and allows the indigenous status of newly-born babies to differ from those of their mothers. the four projection series are labelled main, current, high and low. the main series from the latest projections has the population growing from 246,000 in 2016 to 352,000 by 2046; the indigenous population is expected to increase from 75,000 in 2016 to 104,000 by 2046 while the non-indigenous population is projected to grow from 171,000 to 247,000 over the same projection horizon (nt department of treasury and finance 2019). the nt’s total population is a little under the abs series b projection until the 2040s. the current australian capital territory government population projections start from a jump-off year of 2017 and extend out to 2058 (act government 2019). only one projections series was published. the projections indicate that the population will increase from 412,000 in 2017 to 703,000 by 2058, which is a very similar growth trajectory to the latest abs series b projections. australian population studies 3 (1) 2019 wilson 49 figure 3: some recent projections of state and territory populations notes: state and territory government medium/main series projections are shown. sources: abs (2018a), nsw department of planning and environment (2016), victorian department of environment, land, water and planning (2016), queensland government statistician’s office (2018), western australian planning commission (2018), tasmanian department of treasury and finance (2019), nt department of treasury and finance (2019), act government (2019). 2.3. projections for large sub-state regions the abs projections in population projections, australia include projections for greater capital city statistical areas and balance of state/territory regions. they are produced using a cohortcomponent model projecting internal migration flows in and out of each region constrained to a total net internal migration assumption. the latest series b projections suggest an increasing concentration of population in australia’s metropolitan regions over the coming decades (abs 2018a). the combined population of the capital cities is expected to grow from 16.6 million in 2017 (67.3% of the national population) to 32.1 million by 2066 (75.3%). by the end of the projection horizon sydney and melbourne are projected to be 9.7 and 10.2 million, respectively, with brisbane the next largest at 4.8 million. the greatest proportional increase, however, is projected for greater darwin (149,000 in 2017 and 333,000 in 2066). projections of metropolitan growth such as these tend to gain lots of media attention, but the demographic outcomes for other regions can look very different. the rest of south australia and rest of tasmania are projected to decline in population and experience considerable amounts of population ageing. 50 wilson australian population studies 3 (1) 2019 some state and territory government projections are published for greater capital city statistical areas as well as for other large sub-state regions. in some cases these projections are created directly, but in others they are created by building up from smaller geographical areas. table 1 lists the large sub-state regions for which projections are published in the current sets of projections. in queensland, for example, projections are published for brisbane greater capital city statistical area and all other sa4 regions of the state (queensland government statistician’s office 2018). under the medium series projections brisbane grows from 2.36 million in 2016 to 3.67 million by 2041 (which is very close to the latest abs series b projection). population growth is anticipated for all other regions of queensland with the exception of queensland – outback where the total population remains largely unchanged. table 1: state and territory government projections for large sub-state regions state/territory sub-state regions nsw projection regions, defined as aggregations of local government areas; local health districts vic major regions, defined as melbourne greater capital city statistical area and sa4 areas across the rest of the state qld brisbane greater capital city statistical area and sa4 regions across the rest of the state sa statistical divisions wa no large sub-state regions in the current projections output tas no large sub-state regions in the current projections output nt regions, defined as sa3 areas; sa4 regions act districts, defined as sa3 areas sources: see figure 3. 2.4. projections for local and small areas for many users, local and small area population projections are the most useful. they inform planning, budgeting, and service delivery at the local scale, and small area projections can also be aggregated up to a variety of custom-defined regions. in some cases they can generate strong local reactions, such as objections from a mayor when projections show population decline or little growth, or protests from local community groups about anticipated rapid growth viewed as likely to adversely affect the character and quality of life of a local neighbourhood. the abs does not produce local or small area projections as part of its official projections output (though it does prepare them as a consultancy on behalf of other organisations). the key producers of local and small area projections are state and territory governments who tend to publish local government area (lga) and/or sa2 area projections, as shown in table 2. see box 2 for urls. often local and small area projections in metropolitan regions are derived from cohort-component models linked to housing unit models (foss 2002; wilson 2011), which are based on assumptions about expected future dwelling growth. the incorporation of dwelling data in these projections can result in substantially different outputs compared to trend-based projections. for example, the populations of urban fringe areas experiencing considerable increases in the amount of residential land becoming available will not be projected accurately from trend-based models. but reasonable projections may be obtained via housing-unit models if the land development and dwelling forecasts are about right. australian population studies 3 (1) 2019 wilson 51 table 2: state and territory government projections for local and small areas state/territory areas nsw local government areas vic local government areas; victoria in future small areas (aggregations and modifications of sa2 areas which nest into lgas) qld local government areas; sa2 areas sa local government areas; statistical local areas wa sa2 areas tas local government areas nt no local or small areas in the current projections output act sa2 areas sources: see figure 3 a variety of other organisations also prepare local and small area projections from time to time. the commonwealth department of social services (2014) has published sa2 area projections by age and sex for the whole of australia. they were prepared by the abs as a consultancy and cover a projection horizon of 2012 to 2027, so are a little old now. their main advantage is the use of a common method and data inputs across the whole country. however, the migration assumptions are purely trend-based so projections for sa2 areas within metropolitan regions should be used with caution beyond just a few years into the projection horizon. this also applies to certain nonmetropolitan local areas, such as mining towns (e.g. taylor et al. 2014). the australian electoral commission obtains short-term sa1 area population projections from time to time (usually as a consultancy from the abs). they are used to calculate likely numbers of enrolled electors over the next few years for the purpose of electoral boundary redistributions. the enrolment projections are generally made available, but not the population projections on which they are based (e.g. australian electoral commission 2017). several consulting firms also produce local and small area projections. for example, id prepares projections for many local government areas which are freely available if councils place them on their websites. id also creates smaller geographical areas in its small area forecast information (safi) product (id 2018). pitney bowes produces sa1 area population projections (pitney bowes 2018). the small area projections are prepared on a consulting basis and must be paid for. 3. concluding remarks population projections and forecasts can be very useful inputs to decision-making, policy formulation, budgeting, and planning. but it is important to be aware of their limitations. strictly, population projections, as statements about future population under certain assumptions, are correct provided they have been calculated correctly. this is the case most of the time – but not always. however, population forecasts will almost certainly turn out to be in error to some extent. this can be due to a suboptimal choice of projection model, subsequent revisions to the jump-off population and historical demographic components, random noise, and deviations in actual fertility, mortality and migration from the projection assumptions. as a general rule:  the further a forecast extends into the future the greater the error;  the smaller the population the greater the error; and 52 wilson australian population studies 3 (1) 2019 box 2: selected population projections for australia and where to obtain them population projections produced by the commonwealth government population projections, australia – abs http://www.abs.gov.au/ausstats/abs@.nsf/mf/3222.0 intergenerational report – australian treasury https://treasury.gov.au/intergenerational-report/ an ageing australia – productivity commission https://www.pc.gov.au/research/completed/ageing-australia sa2 population projections – department of social services https://www.gen-agedcaredata.gov.au/resources/access-data/2014/august/population-projections,2012-(base)-to-2027-for-al population projections produced by state and territory governments nsw: population projections – department of planning & environment https://www.planning.nsw.gov.au/projections vic: victoria in future – department of environment, land, water & planning https://www.planning.vic.gov.au/land-use-and-population-research/victoria-in-future-2016 qld: population projections – queensland government statistician’s office http://www.qgso.qld.gov.au/subjects/demography/population-projections/index.php sa: department of planning, transport and infrastructure https://www.saplanningportal.sa.gov.au/data_and_research/population_projections_and_demographics wa: wa tomorrow – department of planning, lands and heritage https://www.dplh.wa.gov.au/information-and-services/land-supply-and-demography/westernaustralia-tomorrow-population-forecasts tas: population projections – department of treasury & finance https://www.treasury.tas.gov.au/economy/economic-data/2019-population-projections-for-tasmaniaand-its-local-government-areas nt: population projections – department of treasury & finance https://treasury.nt.gov.au/dtf/economic-group/population-projections act: population projections – treasury and economic development directorate https://apps.treasury.act.gov.au/snapshot/demography/act population projections produced by overseas organisations world population prospects – united nations population division https://population.un.org/wpp/ population projections by educational status – wittgenstein centre http://dataexplorer.wittgensteincentre.org/wcde-v2/ population projections produced by consulting firms many local and small area projections are produced by consulting firms. summary data may sometimes be freely available but generally these projections must be paid for. examples include: small area forecast information (safi) projections – id https://home.id.com.au/services/population-forecasting/small-area-population-forecasts-safi/ sa1 area projections – pitney bowes https://www.pitneybowes.com/au/data/demographic-data/estimates-projections-australia.html note: urls correct as of 30th april 2019. http://www.abs.gov.au/ausstats/abs@.nsf/mf/3222.0 https://treasury.gov.au/intergenerational-report/ https://www.pc.gov.au/research/completed/ageing-australia https://www.gen-agedcaredata.gov.au/resources/access-data/2014/august/population-projections,-2012-(base)-to-2027-for-al https://www.gen-agedcaredata.gov.au/resources/access-data/2014/august/population-projections,-2012-(base)-to-2027-for-al https://www.planning.nsw.gov.au/projections https://www.planning.vic.gov.au/land-use-and-population-research/victoria-in-future-2016 http://www.qgso.qld.gov.au/subjects/demography/population-projections/index.php https://www.saplanningportal.sa.gov.au/data_and_research/population_projections_and_demographics https://www.dplh.wa.gov.au/information-and-services/land-supply-and-demography/western-australia-tomorrow-population-forecasts https://www.dplh.wa.gov.au/information-and-services/land-supply-and-demography/western-australia-tomorrow-population-forecasts https://www.treasury.tas.gov.au/economy/economic-data/2019-population-projections-for-tasmania-and-its-local-government-areas https://www.treasury.tas.gov.au/economy/economic-data/2019-population-projections-for-tasmania-and-its-local-government-areas https://treasury.nt.gov.au/dtf/economic-group/population-projections https://apps.treasury.act.gov.au/snapshot/demography/act https://population.un.org/wpp/ http://dataexplorer.wittgensteincentre.org/wcde-v2/ https://home.id.com.au/services/population-forecasting/small-area-population-forecasts-safi/ https://www.pitneybowes.com/au/data/demographic-data/estimates-projections-australia.html australian population studies 3 (1) 2019 wilson 53  the greater the volatility of migration the greater the error (smith et al. 2013; wilson et al. 2018). forecast errors are often larger than many users realise. projections and forecasts can also be subject to another form of error – misinterpretation and misreporting. net overseas migration projections are regularly misinterpreted as immigration (which is only correct in the absence of emigration!). sometimes population projections are interpreted as population targets or policies (which would only be correct if a projection had been expressly created as such). for example, the reporting of australia’s population passing the 25 million milestone in 2018 was reported by some news outlets (deliberately not cited) as “33 years ahead of schedule” based on abs projections from the late 1990s, as if those abs projections were part of a national population policy. population projections are highly sensitive to input assumptions, and these can vary considerably from one projection to another (as figure 2 shows). generally assumptions do not attempt to predict trend changes or cyclical paths, but instead aim for a smooth trajectory through the middle of an undulating pattern. assumptions are sometimes based on statistical models, and sometimes on judgement. in reality they often involve a mix of art and science. in australia, overseas migration contributes the bulk of error in national population forecasts while at the state and regional scales both internal and overseas migration tend to contribute most of the error (wilson 2007, 2012). the variability of overseas migration makes it especially challenging to forecast and there is no robust mathematical model available which has proven to give accurate migration forecasts, at least in the medium and long-term (disney et al. 2015). the history of fertility forecasting is also not an unqualified success despite a large literature attempting to understand and forecast period and cohort fertility (bohk-ewald et al. 2018). mortality forecasting at the national scale has been subject to a great deal of research attention and there are an ever increasing number of sophisticated models to choose from (booth and tickle 2008; janssen 2018). generally, errors in mortality forecasts are lower than those of fertility and migration. nonetheless, mortality models are almost all extrapolative models. should a major change in mortality trends occur, as appears to be the case in the us and uk at the moment, errors could be larger than in the past. before using a set of projections, it is valuable to ask who prepared them and why. that may go some way to explaining the choice of projection assumptions and the way in which projection outputs are presented. no set of projections is ever completely objective and free of analysts’ judgments. for example, given the sensitivity about population decline in australia, projections for local areas currently experiencing population decline sometimes err on the ‘optimistic’ side by showing much less decline, or even no decline, in the future. state/territory projections may be influenced by the incumbent government’s view on whether recent population growth is too high or too low, or an explicit population policy. projections produced by consulting firms will sometimes reflect the assumptions, or aspirations, of the client. it is also sensible to conduct a quick assessment of the plausibility of any set of projections you are considering using (see also smith et al. 2013 pp. 385-390; wilson 2017). while most projections have been generated by good models and sensible assumptions, this is not universally the case. treat projections which have been produced using models incorporating net migration numbers or net migration rates with caution (rogers 1990; wilson 2016). they have the potential to generate 54 wilson australian population studies 3 (1) 2019 implausible or impossible outcomes. at the local level in growing urban regions, it is also worth checking that projections are based on anticipated housing developments. be wary of purely trendbased local area projections in such regions. projected age-sex structures should generally evolve slowly and will often maintain characteristic peaks and troughs across the peak migration age groups (late teens to late 30s), as well as continued population ageing. for example, if a local population age structure has a large peak across the late teens and early twenties due to a higher education institution then you would expect that peak to be maintained in the projections. in addition, projected total population, births, deaths and migration flows should follow on smoothly from observed trends – unless there are good reasons for such changes. the projected age pattern of sex ratios should also change gradually in the projections. in summary, this paper has provided a brief guide to australian population projections data at various geographical scales. it has introduced many (though not all) of the projections produced for australia in recent years, and included some brief comments on the limitations of projections. it is hoped that the guide proves a useful starting point for exploring population projections data and understanding the context and broader processes involved in population projections preparation. key messages  population projections are calculations of population beyond the latest population estimate based on assumptions about the future of fertility, mortality and migration.  population projections are used in planning, policy development, service delivery, market assessment, research activities, and public debate.  the abs and state and territory governments are the main producers of population projections and forecasts in australia.  a great deal of projections data and information is now freely available online (box 2).  be aware of the limitations of projections and forecasts. acknowledgements i am grateful for the helpful comments on an earlier draft of this paper by alison taylor, hitesh khanna, abs demography staff, and the anonymous reviewers. references abs (1999) population estimates: concepts, sources and methods, 2009. catalogue no. 3228.0.55.001. canberra: abs. http://www.abs.gov.au/ausstats/abs@.nsf/mf/3228.0.55.001 abs (2013) 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of queensland, brisbane. wilson t (2012) forecast accuracy and uncertainty of australian bureau of statistics state and territory population projections. international journal of population research. volume 2012, article id 419824. http://dx.doi.org/10.1155/2012/419824. wilson t (2016) evaluation of alternative cohort-component models for local area population forecasts. population research & policy review 35(2): 241-261. wilson t (2017) a checklist for reviewing draft population projections. northern institute, charles darwin university. https://www.cdu.edu.au/sites/default/files/the-northern-institute/checklist.pdf. accessed 15 january 2019. wilson t and bell m (2004) comparative empirical evaluations of internal migration models in subnational population projections. journal of population research 21(2): 127-160. wilson t, brokensha h, rowe f, and simpson l (2018) insights from the evaluation of past local area population forecasts. population research and policy review 37(1): 137-155. http://eprints.whiterose.ac.uk/90125/ https://www.treasury.tas.gov.au/economy/economic-data/2019-population-projections-for-tasmania-and-its-local-government-areas https://www.treasury.tas.gov.au/economy/economic-data/2019-population-projections-for-tasmania-and-its-local-government-areas https://population.un.org/wpp/ https://population.un.org/wpp/publications/files/wpp2017_methodology.pdf https://www.planning.vic.gov.au/land-use-and-population-research/victoria-in-future-2016 https://www.dplh.wa.gov.au/information-and-services/land-supply-and-demography/western-australia-tomorrow-population-forecasts https://www.dplh.wa.gov.au/information-and-services/land-supply-and-demography/western-australia-tomorrow-population-forecasts http://dx.doi.org/10.1155/2012/419824 https://www.cdu.edu.au/sites/default/files/the-northern-institute/checklist.pdf australian population studies 2020 | volume 4 | issue 2 | pages 33-38 © kippen 2020. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org australian age-sex-specific covid-19 mortality in international comparative perspective, to june 2020 rebecca kippen* monash university * email: rebecca.kippen@monash.edu. address: school of rural health, monash university, 26 mercy street, bendigo, victoria, australia. paper received 28 july 2020; accepted 9 november 2020; published 16 november 2020 introduction by the end of june 2020, a combination of good luck and good management had resulted in australia having one of the lowest covid-19 death rates in the developed world at that time. australia’s success was heralded nationally and internationally (duckett and stobart 2020; bremmer 2020). the second wave of covid-19 deaths that occurred in australia from july to october 2020 was, in june 2020, only a possible threat. at 30 june 2020, australia had recorded 103 deaths from covid-19, with only 1 death reported in june. this translates to 4 deaths per million population. developed countries with similarly low covid-19 death rates (under 10 deaths per million population), january-june 2020, included japan (8), brunei (7), south korea (6), slovakia (5), singapore (4), and new zealand (4) (calculated from who 2020; united nations 2019). in contrast, the following 11 developed countries had recorded covid-19 death rates more than 50 times higher than that of australia (above 200 deaths per million population), as at 30 june 2020: belgium (842), united kingdom (644), spain (606), italy (575), sweden (528), france (456), united states (382), netherlands (357), ireland (352), chile (298), and canada (227) (calculated from who 2020; united nations 2019). deaths and death rates were still rising strongly in several of these countries in mid-2020. despite vastly differing levels of mortality, age-sex patterns of covid-19 deaths appear to be consistent internationally (at least for those countries with available data). death rates are higher for males than for females, low in childhood and young adulthood, and increase markedly through middle and old age. data and methods this study is based on age-sex-specific covid-19 death rates for the first half of 2020 for 7 developed countries with particularly low or high covid-19 mortality and for which consistent age-sex death data could be sourced. these 7 countries are australia, japan, south korea, belgium, england & wales (constituting 89% of the united kingdom’s population), italy, and the netherlands. d e m o g ra p h ic http://www.australianpopulationstudies.org/ mailto:rebecca.kippen@monash.edu 34 kippen australian population studies 4 (2) 2020 counts of deaths by age and sex were sourced from national governments for australia (agdh 2020) and england and wales (ons 2020), and from coverage-db (riffe et al. 2020) for the remaining 5 countries. population estimates by age and sex for 2020 were sourced from world population prospects (united nations 2019). death counts and population estimates were used to calculate covid-19 death rates for each population by sex for age groups 0-49 (a broad grouping since covid19 mortality under the age of 50 years was relatively low for all considered populations), 50-59, 60-69, 70-79, 80-89, and 90+ years. to show the age-sex covid-19 mortality pattern for each population, taking into account the enormously disparate death-rate levels, rate ratios were used. for each country, the ratio was calculated of the mortality rate for each age-sex category to the mortality rate for males aged 90+ years (the highest age-sex rate for every country considered). these ratios are shown in figure 1. age-standardised mortality rates for each sex for each country were calculated using australia’s 2020 population by age as the standard. these were used to calculate the male-to-female ratio of agestandardised covid-19 mortality for each country, as a summary measure of excess male mortality, shown in figure 2. key features figure 1 shows the age-sex pattern of covid-19 mortality for each country. figure 1a shows 4 populations that have remarkably similar patterns, despite the fact that the overall mortality of 2 of the populations (belgium, and england & wales) was 100-200 times higher than that of the other 2 countries (australia and south korea). for all 4 populations, female covid-19 mortality at age 90+ years was 64-72% that of males of the same age. male and female mortality at age 80-89 years was respectively 34-41% and 23-27% of male mortality at age 90+ years. younger age groups show similar clustered differentials at lower levels. figure 1b displays the remaining 3 populations – japan, italy, and the netherlands (with australia as a comparator) – with dissimilar age-sex patterns of covid-19 mortality, although they all exhibit higher male mortality and a positive correlation of mortality with age. japanese and italian male mortality for age groups under 90 years is relatively high compared to the patterns seen in figure 1a, while japanese female mortality at age 90+ years is remarkably low relative to japanese male mortality at the same age. female mortality at older ages for italy and the netherlands is relatively high. ratios of male-to-female age-standardised covid-19 death rates for each country are shown in figure 2 in order of magnitude. in belgium, australia, netherlands, england & wales, and south korea, age-standardised covid-19 mortality for males was 61-73% higher than for females. in contrast, covid-19 mortality for italian males was more than twice that for females, while japanese male mortality was almost 3 times female mortality. these 7 country-level sex ratios are much higher than those seen for the most similar cause-of-death groupings. for example, for australia in 2019, age-standardised male mortality for certain infectious and parasitic diseases was only 16% higher than female mortality, and for influenza and pneumonia 11% higher (abs 2020). australian population studies 4 (2) 2020 kippen 35 figure 1: similar (1a) and dissimilar (1b) age-sex patterns of covid-19 mortality (rate ratio to mortality for males age 90+ years), selected developed countries, january-june 2020 36 kippen australian population studies 4 (2) 2020 figure 2: male-to-female ratio of age-standardised covid-19 mortality, selected developed countries, january-june 2020 what explains this disparity in sex-specific covid-19 mortality? early research indicates that females produce a more effective immune response to sars-cov-2 (the coronavirus that causes covid-19) than do males, and that this response declines across age for both sexes (takahashi et al. 2020). in addition, co-morbidities (such as hypertension) and risk behaviours (such as smoking and drinking) that are more prevalent in males may play a role in higher male covid-19 mortality (gebhard et al. 2020). areas for future research include the factors behind non-standard age-sex patterns of covid-19 death rates, such as those seen for japan and italy, and reasons for the much higher male-to-female mortality ratios for these countries. in addition, future research will reveal whether the second wave of covid-19 deaths in australia and other countries results in similar age-sex mortality patterns to those seen in the first half of 2020, or whether and why there are substantive differences. limitations although death registration in each country considered is complete, or near complete, covid-19 death rates may be inaccurate because of (a) mis-estimates of the 2020 denominator population, or, more importantly (b) mis-recording of covid-19 as a cause of death. ‘excess deaths’ in 2020 in many countries greatly exceed reported covid-19 deaths (felix-cardoso et al. 2020; the economist 2020). this indicates that covid-19 as a cause of death is under-recorded, and that therefore the death rates discussed above, are, if anything, underestimates. this could also be the case in australia (bennett 2020). the extent of underestimation may vary by age and sex, affecting the age-sex patterns described above. australian population studies 4 (2) 2020 kippen 37 ethics approval this study was approved by the monash university human research ethics committee, project id 25067. acknowledgements the author thanks the editor and two anonymous reviewers whose helpful suggestions improved this work. most data are derived from coverage-db: a database of covid-19 deaths by age (led by researchers at the max planck institute for demographic research), world population prospects (united nations) and coronavirus disease (covid-19) situation reports (world health organization). the author thanks the respective research teams for assembling these international data and making them publicly available under creative commons licenses. references australian bureau of statistics (abs) (2020) causes of death, australia, 2019, catalogue number 3303.0. 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(2020) coverage-db: a database of covid-19 deaths by age. https://osf.io/mpwjq/. accessed 7 november 2020. takahashi t, ellingson m k, wong p, israelow b et al. (2020) sex differences in immune responses that underlie covid-19 disease outcomes. nature. https://doi.org/10.1038/s41586-020-2700-3. accessed 8 november 2020. https://www.abs.gov.au/statistics/health/causes-death/causes-death-australia/2019/3303_1%20underlying%20causes%20of%20death%20%28australia%29.xlsx https://www.abs.gov.au/statistics/health/causes-death/causes-death-australia/2019/3303_1%20underlying%20causes%20of%20death%20%28australia%29.xlsx https://www.health.gov.au/resources/covid-19-deaths-by-age-group-and-sex https://theconversation.com/have-there-been-uncounted-coronavirus-deaths-in-australia-we-cant-say-for-sure-but-the-latest-abs-data-holds-clues-141363 https://theconversation.com/have-there-been-uncounted-coronavirus-deaths-in-australia-we-cant-say-for-sure-but-the-latest-abs-data-holds-clues-141363 https://time.com/5851633/best-global-responses-covid-19/ https://theconversation.com/4-ways-australias-coronavirus-response-was-a-triumph-and-4-ways-it-fell-short-139845 https://theconversation.com/4-ways-australias-coronavirus-response-was-a-triumph-and-4-ways-it-fell-short-139845 https://www.medrxiv.org/content/10.1101/2020.04.28.20083147v1 https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/deaths/datasets/deathsinvolvingcovid19englandandwales https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/deaths/datasets/deathsinvolvingcovid19englandandwales https://osf.io/mpwjq/ https://doi.org/10.1038/s41586-020-2700-3 38 kippen australian population studies 4 (2) 2020 the economist (2020) tracking covid-19 excess deaths across countries. https://www.economist.com/graphic-detail/2020/04/16/tracking-covid-19-excess-deaths-acrosscountries. accessed 2 july 2020. united nations (2019) country-level populations, totals, and by age and sex. world population prospects. https://population.un.org/wpp/. accessed 2 july 2020. world health organization (who) (2020) coronavirus disease (covid-19) situation report 163, 1 july 2020. https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports. accessed 2 july 2020. https://www.economist.com/graphic-detail/2020/04/16/tracking-covid-19-excess-deaths-across-countries https://www.economist.com/graphic-detail/2020/04/16/tracking-covid-19-excess-deaths-across-countries https://population.un.org/wpp/ https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports australian population studies 2021 | volume 5 | issue 1 | pages 1–2 © wilson et al. 2021. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org editorial introduction to the census questions special issue tom wilson* the university of melbourne elin charles-edwards the university of queensland jonathan corcoran the university of queensland julia loginova the university of queensland kirsten martinus the university of western australia * corresponding author. email: wilson.t1@unimelb.edu.au. address: melbourne school of population and global health, the university of melbourne, 207 bouverie st, melbourne, vic 3010, australia. published on 31 may 2021 in june 2020, the australian bureau of statistics announced which new questions would be included in the 2021 census of population and housing, as well as which existing questions would be dropped (abs 2020). there will be new questions about defence force service and long-term health conditions, while the internet access question will no longer be asked given how widespread internet access has become. the process of adding questions to the census questionnaire is, understandably, a lengthy one. proposed new topics and questions require careful consideration and debate. there needs to be a compelling case for asking the question, insufficient data on the topic from existing data sources, clear public acceptability of the question, limited respondent burden, an ability for the question to be easily interpretable, and a strong likelihood of it yielding accurate data, among other considerations (abs 2018a). any potential new question needs to be balanced against the competing demands of both existing as well as other proposed new questions, as well as the value of consistency across censuses for time series analyses. all potential new questions require stakeholder consultation (abs 2018b), detailed abs assessment, and extensive testing. any new questions which successfully make it through this rigorous assessment process into the final abs assessment are then recommended to parliament to be included in the next census. given we are currently in a census year, australian population studies sought to place a spotlight on all things census and put out a special call for short commentary papers on proposed new census topics and questions. this special issue draws together a select number of papers that answered this call. the aim was to broaden the conversation and stimulate useful discussion about potential new topics and questions that might be considered for the 2026 census. contained in this special issue are commentary pieces that cover a range of topics, including (1) measuring multi-locational living; (2) highly mobile populations; (3) long-distance commuting; (4) commuting to places of education; http://www.australianpopulationstudies.org/ mailto:wilson.t1@unimelb.edu.au 2 editorial: wilson et al. australian population studies 5 (1) 2021 (5) financial wellbeing; (6) gender identity and sexual orientation; and (7) ethnicity and ancestry. together we hope readers find the collection of papers thought-provoking and seek to draw on in this special issue as a new consolidated resource for scholars and practitioners interested in the census. we note that some papers did not quite make the timing to appear in this special issue of australian population studies and will instead be published in a special section in the forthcoming november issue of the journal. finally, we would like to thank each of the contributing authors who submitted these interesting commentary pieces, and to the referees who gave their time and provided useful comments on the submitted papers. references abs (2018a) census of population and housing: topic directions, 2021. https://www.abs.gov.au/ausstats/abs@.nsf/lookup/2007.0.55.001main+features12021. accessed 2 may 2021. abs (2018b) census of population and housing: consultation on topics, 2021. https://www.abs.gov.au/ausstats/abs@.nsf/lookup/2007.0main+features12021?opendocum ent. accessed 2 may 2021. abs (2020) 2021 census questions and date announced. https://www.abs.gov.au/ausstats/abs@.nsf/mediareleasesbyreleasedate/9a2c37e441ce868e ca25858b0019a7f0?opendocument. accessed 2 may 2021. https://www.abs.gov.au/ausstats/abs@.nsf/lookup/2007.0.55.001main+features12021 https://www.abs.gov.au/ausstats/abs@.nsf/lookup/2007.0main+features12021?opendocument https://www.abs.gov.au/ausstats/abs@.nsf/lookup/2007.0main+features12021?opendocument https://www.abs.gov.au/ausstats/abs@.nsf/mediareleasesbyreleasedate/9a2c37e441ce868eca25858b0019a7f0?opendocument https://www.abs.gov.au/ausstats/abs@.nsf/mediareleasesbyreleasedate/9a2c37e441ce868eca25858b0019a7f0?opendocument australian population studies 2019 | volume 3 | issue 2 | pages 41-44 © arringer, sigler and charles-edwards 2019. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org residential concentration patterns of immigrant groups in australia’s major cities renee arringer* the university of queensland thomas sigler the university of queensland elin charles-edwards the university of queensland * corresponding author. email: renee.arringer@uqconnect.edu.au. address: school of earth and environmental sciences, chamberlain building, the university of queensland, st lucia 4072, queensland, australia paper received 7 september 2019; accepted 17 october 2019; published 18 november 2019 immigration is a global process that stems from a range of personal motivations including the prospect of higher income, better access to education and health, and improved living conditions (undp 2009). this is reflected in australia’s migrant profile where, as of the 2016 census, almost half of the population were either born overseas or had at least one parent born overseas (abs 2017a). ethnic diversity is continuously rising in australia; however, migrants remain overwhelmingly concentrated in the major australian cities of sydney, melbourne, brisbane, and perth. this concentration extends to the suburb scale, as specific neighbourhoods are home to large numbers of co-ethnic communities. an extensive literature (e.g. burnley 2005; edgar 2014; forrest and sheshkin 2015; portes and zhou 1993) indicates that concentration can be involuntary (e.g. ghetto formation) or voluntary, where community members benefit from proximity to others speaking their language or sharing their cultural and social values. this demographic shows the changing residential concentration of the largest immigrant groups in australia’s four most populous cities between 2006 and 2016. it includes both migrants settled in australia and those who immigrated during the five years prior to the 2006, 2011, and 2016 censuses. the immigrant groups were selected as those comprising australia’s ten largest migrant stocks in 2016 (concerned with the birthplace of current immigrants living in australia) and those with the ten largest migrant flows in 2016 (the number of immigrants entering australia). stocks were based on abs estimated resident populations by country of birth in 2016 (abs 2017b) and flows were based on data from the department of home affairs (department of home affairs 2018). when combined, these yielded a total of 13 selected countries of birth: china, england, india, ireland, italy, malaysia, nepal, new zealand, pakistan, philippines, scotland, south africa, and vietnam. country of birth data were extracted from the 2006, 2011, and 2016 censuses based on a harmonised geography and extracted by statistical areas level 2 (sa2) for each greater capital city statistical area (gccsa). these data were used to calculate the index of dissimilarity for each d e m o g ra p h ic http://www.australianpopulationstudies.org/ mailto:renee.arringer@uqconnect.edu.au 42 arringer, sigler & charles-edwards australian population studies 3 (2) 2019 immigrant group in comparison to the australian-born population. the index of dissimilarity is defined as: 𝐼𝐷 = 1 2 ∑ |𝑥𝑖 − 𝑦𝑖| 𝑖 where 𝑥 is the percentage of australian-born population in category 𝑖 (sa2) and 𝑦 is the percentage of immigrant-group population in category 𝑖 (sa2). values close to zero indicate that little dissimilarity exists while high values denote high levels of dissimilarity. plotting dissimilarity against the absolute population of each group reveals the progression of residential concentrations between groups the demographic in figure 1 represents the progression of each immigrant group’s residential concentration as a series of plotted lines. the colour of each line represents the immigrant group, and the shape of the first data point represents the city (circle = brisbane; triangle = melbourne; diamond = perth; square = sydney). the arrows signal the directionality of absolute population change for each group, as well as the degree of relative concentration, as measured by the index of dissimilarity. all groups, except for italy-born and the scotland-born (melbourne and sydney) grew between the 2006 and 2016 census. over this same period, most groups became more dissimilar, with only the italy-born (brisbane and sydney); south africa-born (brisbane and melbourne), vietnam-born (brisbane, perth and sydney) and nepal-born (brisbane), becoming less concentrated. the latter reflects rapid population growth from a low base. from figure 1, it appears that immigrant groups disperse into two modes of settlement, with one converging towards dissimilarity of around 10-20 (england, ireland, new zealand, scotland, and south africa) and the other converging towards dissimilarity of around 50 (china, india, malaysia, nepal, pakistan, philippines, and vietnam). italian immigrant groups depart from this trend, fluctuating between dissimilarities of 30 and 40 for all cities, with group size remaining stagnant or decreasing. for groups converging around dissimilarity of 10-20, there is an observable increase in dissimilarity over the three census years as group size increases (excluding scotland). groups located in sydney, melbourne, and perth increase in dissimilarity as they increase in size until 2011. after this point they continue to increase in size, but their dissimilarity decreases. brisbane is an exception to this pattern, with the majority of groups maintaining a steady directionality. the results show that with the exception of very small groups (e.g. nepal-born in perth, vietnam-born in brisbane and perth), the residential patterns of the largest non-australian born groups are becoming more dissimilar over time. when other research is consulted (burnley 2005; edgar 2014; forrest and dandy 2018), these results suggest that factors surrounding ethnicity – particularly english language proficiency – can influence the level of segregation experienced by immigrant groups in australia. it also suggests immigrant groups will not necessarily become completely ‘assimilated’ into australian society (i.e. dissimilarity = 0) after a certain period, as shown by early-immigrant groups such as those born in italy. as the demographic shows, dissimilarity can increase as group size grows, suggesting that group size may be one variable affecting co-ethnic residential preference. the results presented suggest the need for new models of urban residential settlement to better reflect australia’s ever-changing immigration profile. understanding how group-level characteristics australian population studies 3 (2) 2019 arringer, sigler & charles-edwards 43 (such as size) determine residential concentration is critical as australian cities become increasingly diverse in numbers and origins of immigrant groups. figure 1: residential concentration patterns of the largest immigrant groups in australia’s major cities, 2006-16 source: australian bureau of statistics 2006, 2011, and 2016 census data notes: ‘dissimilarity’ values represent the index of dissimilarity for each immigrant group. ‘group size’ is the total populations of immigrant groups represented on a logarithmic scale. country abbreviations: china (chn), england (eng), india (ind), ireland (irl), italy (ita), malaysia (mys), nepal (npl), new zealand (nzl), pakistan (pak), philippines (phl), scotland (sct), south africa (zaf), vietnam (vnm). the letter preceding the country abbreviation corresponds to brisbane (b), melbourne (m), perth (p), or sydney (s). references abs (2017a) census of population and housing: australia revealed, 2016. catalogue no. 2024.0. canberra: abs. abs (2017b) migration, australia, 2015-16. catalogue no. 3412.0. canberra: abs. alba r d and nee v (2003) remaking the american mainstream: assimilation and contemporary immigration. cambridge: harvard university press. burnley i (2005) generations, mobility and community: geographies of three generations of greek and italian ancestry in sydney. geographical research 29(4): 379-392. 44 arringer, sigler & charles-edwards australian population studies 3 (2) 2019 department of home affairs (2018) country profiles. canberra: australian government. https://www.homeaffairs.gov.au/research-and-statistics/statistics/country-profiles/profiles. accessed 21 february 2018. edgar b (2014) an intergenerational model of spatial assimilation in sydney and melbourne, australia. journal of ethnic and migration studies 40(3): 363-383. forrest j and dandy j (2018) proficiency in english, linguistic shift and ethnic capital: an intergenerational analysis of non-english speaking background immigrant groups in sydney, australia. journal of multilingual and multicultural development 39(2): 111-123. forrest j and sheshkin i (2015) strands of diaspora: the resettlement experience of jewish immigrants to australia. journal of international migration and integration 16(4): 911-927. portes a and zhou m (1993) the new second generation: segmented assimilation and its variants. the annals of the american academy of political and social science 530: 74-96. undp (2009) human development report 2009: overcoming barriers: human mobility and development. new york: undp. https://www.homeaffairs.gov.au/research-and-statistics/statistics/country-profiles/profiles australian population studies 2020 | volume 4 | issue 2 | pages 39-47 © loginova & wohland 2020. published under the creative commons attribution-noncommercial licence 3.0 australia (cc by-nc 3.0 au). journal website: www.australianpopulationstudies.org introductory guide how to create an interactive dashboard using r: the example of the queensland covid-19 tracker julia loginova* the university of queensland pia wohland the university of queensland * corresponding author. email: j.loginova@uq.edu.au. queensland centre for population research, school of earth and environmental sciences, chamberlain building, the university of queensland, st lucia, qld 4072, australia paper received 15 september 2020; accepted 2 november 2020; published 16 november 2020 abstract background interactive tools like data dashboards enable users both to view and interact with data. in today’s data-driven environment it is a priority for researchers and practitioners alike to be able to develop interactive data visualisation tools easily and where possible at a low cost. aims here, we provide a guide on how to develop and create an interactive online data dashboard in r, using the covid-19 tracker for health and hospital regions in queensland, australia as an example. we detail a series of steps and explain choices made to design, develop, and easily maintain the dashboard and publish it online. data and methods the dashboard visualises publicly available data from the queensland health web page. we used the programming language r and its free software environment. the dashboard webpage is hosted publicly on github pages updated via github desktop. results our interactive dashboard is available at https://qcpr.github.io/. conclusions interactive dashboards have many applications such as dissemination of research and other data. this guide and the supplementary material can be adjusted to develop a new dashboard for a different set of data and needs. key words interactive dashboards; r; data visualisation; covid-19; queensland http://www.australianpopulationstudies.org/ mailto:j.loginova@uq.edu.au https://qcpr.github.io/ 40 loginova & wohland australian population studies 4 (2) 2020 1. introduction researchers and practitioners increasingly rely on interactive visualisation tools to draw insights from their data, improve strategic and operational decision-making and to disseminate information to stakeholders and the wider public. effective interaction with data can substantially enhance the understanding of underlying trends and patterns. one way to achieve this is by presenting data in a dashboard. dashboards are “a visual display of the most important information needed to achieve one or more objectives, consolidated and arranged on a single screen so the information can be monitored at a glance.” (few 2006, p. 12). dashboards are attractive to users as they amplify cognition and capitalise on human perceptual capabilities. they can be broadly categorised as interactive or static. interactive dashboards represent a new trend of data intelligence that enable not only viewing but also interacting with data through tables, charts, maps and text. these are different from static dashboards that are “read-only” (yigitbasioglu and velcu 2012). interactivity is especially useful in presenting and interpreting large complex data, as it assists in summarising data and alleviating information overload. different techniques and software can be used to present information and provide interactivity (smith 2013). the possible options are arcgis dashboards, tableau, as well as numerous tools developed for the purposes of data intelligence. although providing numerous advantages and appealing aesthetics, they might not be well integrated with the process and outputs of research which is performed in r, a widely used software environment for statistical computing, data science, and graphics. r is often used in conjunction with the integrated development environment rstudio. both are available as free and open-source editions with a range of packages and exemplary support. the following section explains the process of development of the queensland covid-19 tracker in r. 2. queensland covid-19 tracker in r as the covid-19 pandemic started to spread around the world and australia, dashboards that visualise a large amount of rapidly changing information have become useful for the general public and government institutions. examples include the dashboard by the world health organisation (who 2020) and covid-19 map coordinated by johns hopkins coronavirus resource center (dong et al. 2020). numerous interactive web-dashboards have been developed to track the spread of covid19 in australia, for example, covid-19 dashboard developed by government of south australia (2020), new south wales covid-19 cases and community profile by the university of sydney (2020), charting the covid-19 spread in australia by the australian broadcasting corporation (abc 2020), and covid live (2020) developed by volunteers. covering data at the level of states and territories, these dashboards initially did not provide information related to the spread of covid-19 on a smaller geography level. we aimed at filling this gap through the development of the covid-19 tracker focused on queensland regions. to this end, we wanted to effectively utilise publically available information from queensland health (2020a), a ministerial department of the queensland government, and provide interactive analytical features to track the spread of covid-19 throughout time and space. australian population studies 4 (2) 2020 loginova & wohland 41 2.1. setup several r packages provide opportunities for the development of interactive dashboards. the queensland covid-19 tracker has been developed using the r package ‘flexdashboard’ (iannone et al. 2020). it provides an effective solution for developing and publishing a group of related data visualisations as a dashboard. another package that could be used is ‘shinydashboard’ (chang and borges 2018). it is more suitable for developing dynamic dashboards where input interacts with the output requiring a server to execute r code on user input. ‘flexdashboard’ operates as an r markdown framework allowing the dashboard to be ‘knitted’ into a dynamic but independent html. the complete and annotated code in r markdown document “queenslandcovid19tracker.rmd” and associated files to create the queensland covid-19 tracker are published online (loginova and wohland 2020). as demonstrated in this document, the first step in setting up the dashboard is to add the yaml code as the header of the dashboard, including title and type of output file which in this case is html (box 1). the rest of the document contains code to specify the outline of the dashboard and numerous code chunks. a code chunk is a piece of r code that start and end with ``` and can be named. in the code chunk ‘setup’, we assign main directory (the folder where “queenslandcovid19tracker.rmd” and data files were downloaded), install and load packages, and set global options that affect how r displays the results. it is important to stress that versions of r, r studio and r packages may affect the execution of the code. therefore, control of r and packages is necessary to ensure the stability of the dashboard over time. to this end, we indicated that the code for the queensland covid-19 tracker was developed and works in r version 4.0.0 and versions of each package are specified in “queenslandcovid19tracker.rmd”. -- title: "covid-19 in queensland, australia" output: flexdashboard::flex_dashboard -- box 1: the yaml code specifying the header of the dashboard 2.2. data updates and calculations queensland health has published summary data for 16 queensland health and hospital regions on a daily basis since the first cases of covid-19 were identified in queensland on january 21st 2020 (queensland health 2020b). we started gathering data from march 16th 2020, at the point when the number of new cases had begun to increase rapidly. as this paper went to press in november 2020, there were 1,177 confirmed cases of covid-19 in queensland. the data for confirmed, new confirmed, active and recovered cases as well as deaths were downloaded daily from the 42 loginova & wohland australian population studies 4 (2) 2020 queensland health website (queensland health 2020a) and combined in a .csv (comma-separated values) file. as the situation evolved, additional information has been included in the reporting, including the number of active self-quarantine notices. data updates, preparation, and calculations are performed in a single r markdown file. in the code chunk ‘updates’, we load updated data into the r environment, specify values to update, and add updated daily data to existing data files. in ‘data preparation’, we format the data to be used in maps and graphs. in ‘calculations’, we obtain values to be displayed in the dashboard for queensland totals and doubling time (the time it takes for confirmed cases to double in value). it is important to stress that these three code chunks contain ‘include = false’ condition to prevent r from showing the code and its results in the dashboard 2.3. layout, design and components the layout of the dashboard is specified in the r markdown document using ‘flexdashboard’ syntax, as shown in box 2. the layout of the queensland covid-19 trackers includes four pages organised according to themes, including ‘situation today’, ‘change over time’, ‘individual regions’, and ‘about’. the first three pages contain a collection of tabsets to visualise information relevant to each page (figure 1). the layout of each page can be column-based or row-based, allowing control of the width of columns. the colour of the main panel (dark purple) has been assigned at the beginning of the r markdown document using css (cascading style sheets) easily understood by html (see code for