Luy_Pötzsch_Englisch.indd Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany, 1955-2008 Marc Luy, Olga Pötzsch Abstract: In this article we present estimates of the tempo-adjusted total fertility rate in Western and Eastern Germany from 1955 to 2008. Tempo adjustment of the total fertility rate (TFR) requires data on the annual number of births by parity and age of the mother. Since offi cial statistics do not provide such data for West Ger- many as well as Eastern Germany from 1990 on we used alternative data sources which include these specifi c characteristics. The combined picture of conventional TFR and tempo-adjusted TFR* provides interesting information about the trends in period fertility in Western and Eastern Germany, above all with regard to the differences between the two regions and the enormous extent of tempo effects in Eastern Germany during the 1990s. Compared to corresponding data for popula- tions from other countries, our estimates of the tempo-adjusted TFR* for Eastern and Western Germany show plausible trends. Nevertheless, it is important to note that the estimates of the tempo-adjusted total fertility rate presented in this paper should not be seen as being on the level of or equivalent to offi cial statistics since they are based on different kinds of data with different degrees of quality. Keywords: Germany · Fertility · Fertility trends · Tempo adjustment · Tempo-adjusted TFR · Bongaarts – Feeney · Total fertility rate · East-West comparison · Parity · Biological birth order · Average age at childbirth 1 Introduction The East-West German differences in fertility trends which have been observed over many decades are probably the most frequently studied aspect of the demo- graphic differences between Eastern and Western Germany. Above all the changes in Eastern German fertility have been frequently studied in recent years (e.g. Dorb- ritz 1992; Menning 1995; Witte/Wagner 1995; Conrad et al. 1996; Beck-Gernshe- im 1997; Dorbritz 1997; Sackmann 1999; Lechner 2001; Sobotka 2002; Kreyenfeld 2003; Kreyenfeld 2009), and are regarded as the main characteristic of the “demo- graphic shock” experienced by the population in the new Federal Länder after the Comparative Population Studies – Zeitschrift für Bevölkerungswissenschaft Vol. 35, 3 (2010): 605-636 (Date of release: 15.09.2011) © Federal Institute for Population Research 2011 URL: www.comparativepopulationstudies.de DOI: 10.4232/10.CPoS-2010-14en URN: urn:nbn:de:bib-cpos-2010-14en2 • Marc Luy, Olga Pötzsch606 political changes (Eberstadt 1994). The level of fertility and its changes over time are particularly important because they have the strongest long-term impact on the age structure of a population (Luy 2009). This is why the determinants of fertility and of childlessness in the context of the specifi c backgrounds of life in Western and Eastern Germany have been analysed intensively in recent years (e.g. Dorbritz/ Schwarz 1996; Hank 2002; Dornseiff/Sackmann 2003; Hank/Kreyenfeld 2003; Hank et al. 2004; Butterwege et al. 2005; Eckhard 2006; Boehnke 2007; Bernardi/Keim 2007; Bernardi et al. 2008; Arránz Becker et al. 2010; Pötzsch 2010). For most politically and socially relevant questions the absolute numbers of births are of primary interest since these determine the future numbers of kinder- garten children, school pupils, students, employed persons or pensioners, albeit the size of these population groups is additionally determined by mortality and mi- gration. Demographic fertility research, by contrast, studies primarily the relative fertility quantum in order to be able to describe changes and differences between populations and to identify the corresponding determinants and infl uencing factors. The demographic indicator used most frequently in the fi eld of period analysis – i.e. the analysis of fertility conditions in a specifi c calendar year – is the “total fertility rate” (TFR) which is often interpreted as the “average number of children”. However, it is generally diffi cult in the period analysis to give a specifi c meaning to such meas- ures. This is only possible in the cohort perspective, in which the fertility of a real cohort is analysed year by year on a longitudinal basis. Period analysis, by contrast, summarizes the fertility of a specifi c calendar year using the age-specifi c fertility rates of all women who were between 15 and 49 years old in this calendar year. By summing up the age-specifi c fertility rates to the total fertility rate, a hypothetical cohort is constructed which is supposed to represent the current fertility conditions (see Sobotka and Lutz 2010 on the problem of the use of the period TFR for ques- tions of political and societal relevance). The observed or reconstructed number of births of women belonging to a cer- tain cohort can be infl uenced by specifi c period and cohort effects. In general, these effects are not seen as distortions, but rather as causal determinants of cohort fer- tility and are thus of central interest of the analysis. Period analysis, by contrast, aims to describe the “pure” fertility level of a specifi c calendar year– the so-called “quantum of fertility” – without including any other structural factors determining or infl uencing the level of fertility. A classical structural factor infl uencing the overall fertility level is the age composition of a population, which can have a major impact on the number of births. Thus, demographic period indicators such as the TFR are calculated as age-standardised measures. (Although cohort indicators are gener- ally calculated age-standardised as well, no comparable distortion effects of the age composition can occur here). At the end of the 1990s, Bongaarts and Feeney (1998) showed that changes in the average age at childbirth occurring during a calendar year alter fertility rates and hence the TFR, a phenomenon that has been described already by Hajnal (1947). Bongaarts and Feeney (1998) referred to this alteration of the TFR as a “tempo ef- fect” and proposed to not only standardize the total fertility rate by age, but to also adjust the TFR for tempo effects. The basic idea of Bongaarts and Feeney is that Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 607 tempo effects are also a structural factor distorting the TFR when this indicator is used to refl ect the pure quantum of current fertility. An increase in the average age at childbirth during the analyzed calendar year leads to a tempo effect-caused reduction in the fertility rates, and a reduction in the average age at childbirth leads to a tempo effect-caused increase in the fertility rates. Even though the existence of such tempo effects in the period TFR is not questioned among demographers, opinions as to the need for the tempo adjustment diverge in some respects. None- theless, the additional use of the tempo-adjusted total fertility rate, which is sym- bolised by TFR*, has more and more become the standard in demographic fertility research in recent years. This can be seen in the increasing number of publications in which fertility trends and differentials are analysed not only on the basis of the conventional TFR, but also using the TFR* (e.g. Lesthaeghe/Willems 1999; Philipov/ Kohler 2001; Goldstein et al. 2003; Sobotka 2003, 2004a, 2004b; Frejka/Sobotka 2008; Goldstein et al. 2009). The TFR* is also a part of the standard repertoire of de- mographic indices compiled in the “European Demographic Datasheet”, published every two years by the Vienna Institute of Demography of the Austrian Academy of Sciences (available on the Internet at http://www.oeaw.ac.at/vid/datasheet/index. html). In most of the above mentioned publications, however, information on the tem- po-adjusted TFR* is missing for some European populations, including Germany. The calculation of the tempo-adjusted TFR* requires the number of births being separated not only by age of the mother but also by parity. This information was not available for unifi ed Germany and for former West Germany until 2009 because of the statutory regulations. Prior to 2009, the parity was exclusively collected for births of married mothers, with the birth order referring solely to children of the current marriage (including pre-maritial children with the current husband). Pre- maritial children with fathers other than the mother’s current husband, as well as children from previous marriages, have not been considered and thus did not en- ter offi cial population statistics on parity. Only after the supplement of the Popula- tion Statistics Act in 2009 (Bevölkerungs statistik gesetz/Federal Law Gazette [BGBl] 2007) it was possible to record the so-called “biological birth order” independently of the civil status of the mother for the whole of Germany (see Statistisches Bunde- samt 2010). For the new Federal Länder (eastern Germany), the data of the former GDR are available for the period prior to 1989. These include all births by parity and year of birth of the mother as required for tempo adjustment. After reunifi cation, however, the birth statistics were carried out in accordance with the Federal Population Sta- tistics Act, and thus no offi cial data on births by biological parity is available for Eastern Germany for the period from 1989 to 2008. This article aims to provide estimates for the TFR* in Western and Eastern Ger- many from the mid-1950s to the present, and hence to close – at least partly – one of the gaps in international fertility research. In order to separate births by parity as required for tempo adjustment of the TFR, we have used a variety of alternative sources for West Germany as well as for Eastern Germany from 1990 on. These con- tain estimates for the number or proportion of births by parity and age of the mother • Marc Luy, Olga Pötzsch608 for different periods, but they are based in some cases on very small population samples with questionable representativity for the overall population. Moreover, in view of the educational and family bias usually found in survey data, it cannot be ruled out that some of these data sources lead to systematic distortions in estimat- ing parity and age at childbirth. Another inaccuracy results from the fact that the data covers different age ranges of the reproductive life span. Although the tempo- adjusted fertility rates derived from these data are rather plausible when compared to corresponding estimates for other countries with better data bases, it is impor- tant to note that the estimates presented in this paper should not be seen as being on the level of or equivalent to offi cial statistics since they are based on different kinds of data with different degrees of quality. The methods, and above all the data, on which our estimates of the TFR* for Germany are based are described in detail in the next section. Then we present the results for Western and Eastern Germany both in an intra-German as well as in an international comparison. Finally, we summarise the most important fi ndings and discuss briefl y interpretation-related and methodical aspects of the tempo-adjusted total fertility rate. Note that the latter issue as well as a detailed analysis of the fer- tility trends in Western and Eastern Germany are not the central purpose of this paper. Nonetheless, the advantages and disadvantages of the tempo-adjusted TFR* should be at least briefl y summarised for those who have not followed the very de- tailed discussion on tempo adjustment or those who have not studied it in detail. 2 Data and methods The conventional total fertility rate (TFR), which is published by the German Federal Statistical Offi ce on an annual basis, is calculated from the sum of the age-specifi c fertility rates f(x), which are calculated by dividing the number of all births of women aged x, B(x), by the number of women aged x, P(x): Since all indicators in this article refer to periods, we refrain from using an ad- ditional index for the calendar year as far as possible for reasons of simplifi cation. The parameters α and ß represent the lowest and highest ages of women’s repro- ductive life span, which are usually defi ned as 15 and 49 years. When totalling the age-specifi c fertility rates, they all take on the same weight in the resulting TFR, so that – as has already been mentioned in the introduction – the TFR primarily consti- tutes an age-standardised fertility indicator. The basic idea behind tempo adjustment of the TFR is not only to standardize for age but also for shifting effects which emerge in a calendar year when the average age of women at childbirth changes during that calendar year (see Bongaarts/Feeney 1998, 2006, 2010). The direction of these changes can differ between parities. Since )x(P )x(B )x(fTFR . (1) Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 609 the parities take on different weights in the overall TFR, the tempo adjustment of the TFR according to the method of Bongaarts and Feeney (1998) is performed on a parity-specifi c basis. This requires separating the TFR in its parity-specifi c com- ponents. The TFR for a parity i is calculated by summing up the corresponding age- and parity-specifi c fertility rates f(x)i which differ from the age-specifi c fertility rates in equation (1) in that the numerator does not contain all births of women aged x, but only births of parity i, B(x)i: Note that these age- and parity-specifi c fertility rates f(x)i are no probabilities (or any related measure) of the transition of a parity i to the next parity i+1. For this purpose, the denominator of the rates should not include all x-year-old women, but only those who actually belong to the female population at risk of giving birth to a child of the i-th birth order (e.g. childless women in the calculation for parity 1). The age- and parity-specifi c fertility fi gures from equation (2) rather represent the elements of a purely formal parity-specifi c decomposition of the TFR as can be demonstrated easily. Subdividing the age-specifi c numbers of births B(x) in equa- tion (1) into the parities B(x)1 (fi rst births), B(x)2 (second births), B(x)3 (third births) and B(x)4+ (fourth and further children), leads to which can be reformulated to so that follows Tempo adjustment with the method proposed by Bongaarts and Feeney (1998) is done within the parity-specifi c TFRi. Therefore, the TFRis are divided by one minus the annual change in the average age at childbirth of parity i, ri, so that the tempo- adjusted parity-specifi c TFRi* results from P(x) B(x) )x(fTFR iii . (2) P(x) B(x)B(x)B(x)B(x) TFR 4321 , (3) P(x) B(x) P(x) B(x) P(x) B(x) P(x) B(x) TFR 4321 , (4) 4 1i iTFRTFR . (5) • Marc Luy, Olga Pötzsch610 The change in the average age at childbirth of parity i can be estimated by halv- ing the difference between the average parity-specifi c age at childbirth, MABi, in the following year and the preceding year (see Bongaarts and Feeney 1998). If we denote the analyzed calendar year with t, the estimate for ri(t) results from We calculated the average parity-specifi c ages at childbirth MABi on an age- standardised basis from the age- and parity-specifi c fertility rates by In accordance with the relations expressed in equations (3), (4) and (5) the over- all tempo-adjusted fertility rate TFR* results from the sum of the tempo-adjusted parity-specifi c TFRi*s: Tempo adjustment of the total fertility rate requires the number of births to be subdivided by the age of the mothers on a parity-specifi c basis. The offi cial statis- tics of the GDR (East Germany) recorded all births by parity and year of birth of the mother, and thus the tempo-adjusted TFR* for East Germany for the period 1955 to 1987 can be directly estimated from these data. For the new Federal Länder since unifi cation in 1990 (Eastern Germany) as well as for the territory of the former Fed- eral Republic of Germany (West respective Western Germany), offi cial data on the biological birth order are only available since 2009. In order to carry out the parity- specifi c subdivision of the birth numbers necessary for the tempo adjustment of the TFR for West respective Western Germany and Eastern Germany from 1990 onwards, it was necessary to use alternative data sources: Birg et al.• (1990) provided an estimate of the parity-specifi c subdivision of births in the Federal Republic of Germany for the years 1958 to 1985. The estimates were based on the family biographies collected in the context of the research project entitled “Labour market dynamics, family development i i i r1 TFR *TFR . (6) 2 1)(tMAB1)(tMAB (t)r iii . (7) i i i f(x) f(x)0,5)(x MAB . (8) 4 1i i *TFR*TFR . (9) Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 611 and generative conduct” in 1986, promoted by the DFG, which included 793 women and 783 men of the cohorts born in 1950 and 1955 from Düssel- dorf, Hannover, Bochum, Gelsenkirchen, Gronau, Ahaus, Vreden and Leer. For each child of these respondents, the family biographies contain both the actual birth order and the birth order information used by the West German Statistical Offi ce at that time. From the corresponding relative frequencies (obtained for single ages of the mothers by means of linear regression mod- elling), both the parity-specifi c births in marriage, and the non-marital births which were recorded in offi cial statistics on a non-parity-specifi c basis, were transferred into an estimate of the biological parities by single age of the mother. The authors used constant parity-specifi c subdivisions as obtained from the project sample for both the children born in wedlock and those born out of wedlock for every year from 1958 to 1985. Kreyenfeld• (2002) combined the offi cial birth numbers for West respective Western Germany from 1985 to 1995 with parity-specifi c frequencies de- rived from the Socio-Economic Panel (SOEP) similarly to Birg et al. (1990). However, only the non-marital births of the SOEP samples for West/Western Germany and for foreigners (211 cases in total) were used for the subdivision into the respective birth orders by means of a time-variable multinomial logit model. As a consequence of this modelling procedure, the estimated age- specifi c parity distributions differ slightly from year to year, in contrast to the estimates of Birg et al. (1990). For marital births, Kreyenfeld (2002) used the offi cial data on birth order of parents who were married to one another. For the years 1995 to 1999 (Western Germany) and 1995 to 2000 (Eastern • Germany) we could use the data of the perinatal survey compiled and kindly made available by Dr. Manfred Voigt (University of Greifswald). This survey has been carried out since the 1980s directly in West German birth clinics with the aim of improving the quality of perinatal medicine. Participation in the survey, which was conducted by the Bundesländer themselves until 2000, has been obligatory for all clinics since 1995 (see Goerke/Lack 2000; Kreyenfeld et al. 2010). In contrast to offi cial statistics, the perinatal survey includes the birth order for all births a woman has ever had. Because of the aim and the method of the survey, the perinatal survey exclusively contains births which took place in clinics, what applies to the majority of all births in Germany. Dr. Voigt was able to collect the perinatal survey data for all the Federal Länder with the exception of Baden-Württemberg. Despite the ob- ligatory participation for all hospitals, the dataset for the years 1995 to 1997 contains only approx. 70 % of all 1,656,339 births registered in Germany during these years. The percentages for the single calendar years are about 65 % in 1995, 78 % in 1996 and 66 % in 1997. Nevertheless, the availability of the data for the Federal Länder enabled us to estimate parity-specifi c propor- tions of births by the age of the mothers for Eastern and Western Germany separately. For this purpose we used the absolute numbers without addi- • Marc Luy, Olga Pötzsch612 tional smoothing. Since Berlin is included as one overall unit in the perinatal survey – as in the offi cial statistics from 2000 onwards – we excluded the capital from our analysis. Kreyenfeld et al• . (2010) also used the data of the perinatal survey, which have been compiled for the whole federal territory since the beginning of the 21st Century by the German National Institute for Quality in Healthcare (Bundes- geschäftsstelle Qualitätssicherung), to estimate parity-specifi c birth num- bers for the years from 2001 to 2008. But also these data are only virtually complete from 2004 onwards. Some hospitals as well as entire Bundesländer are missing in the years before, such as Hessen, Schleswig-Holstein and the Saarland in 2001. The authors report that 4,978,381 births are recorded (and useable) for the entire period from 2001 to 2008, corresponding to 89 % of all births registered in Germany in these years. The shares in 2001, 2002 and 2003 are however only between 62 and 85 %. Kreyenfeld et al. (2010) pro- vide the parity-specifi c birth numbers derived from these data separately for Eastern and Western Germany, with all of Berlin being allocated to Eastern Germany. Like the data from the perinatal survey from 1995 to 1999 respec- tive 2000 (see above), the data used by Kreyenfeld et al. (2010) are based solely on births which took place in hospitals. Using data from Germany’s offi cial health reporting (Gesundheitsberichterstattung des Bundes) and sta- tistics of the Association for Quality in Out-of-Hospital Births (Gesellschaft für Qualität in der außerklinischen Geburtshilfe e.V. – QUAG), the authors found that roughly one to two percent of all births took place outside hospi- tals between 2001 and 2008. Although these fi gures include primarily higher- parity births, taking them into account only leads to negligible changes in the parity-specifi c subdivision derived from the data of the perinatal survey (see Kreyenfeld et al. 2010). In order to close the gap arising from the above mentioned data sources • for Western Germany in the year 2000, we also analyzed the parity-specifi c birth numbers of offi cial statistics for the period 1998 to 2002. As has al- ready been described, these fi gures only include children born to parents who are currently married to one another including their joint pre-marital children. The quality of the TFR* estimated on the basis of these data mainly depends on the extent of deviations between the average age at childbirth of the women by the biological birth order and by the birth order in the current marriage. Analysing the new offi cial statistics for 2009 one asserts that this extent mainly depends on the proportion of non-marital births (Statistisches Bundesamt 2010). The difference between the age of the mother at the fi rst birth in the current marriage and the age of the mother at the fi rst birth in her life was 0.9 years in Western Germany in 2009 with the proportion of extra- marital fi rst births being 36 %. The proportion of extra-marital births was smaller among second and further births, namely between 17 % and 19 %, and the corresponding age difference was only 0.3 years. The infl uence of Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 613 re-marriage was weak: 93 % of fi rst births in the current marriage in 2009 were also the fi rst births in the life of the mother. The concordance between biological and marital birth order was even larger in second and further births. Thus, since the proportion of births of unmarried women among all live births in Western Germany in the years 1998 to 2002 was between 16 % and 21 % (Statistisches Bundesamt 2008, Tab. 1.1.1 to 1.1.3), the information on the marital birth order forms a relatively sound basis for estimating the TFR*. The situation for Eastern Germany is different what prohibits using the information from offi cial statistics on the marital birth order: The proportion of extra-marital births is much larger than in Western Germany. The propor- tion of extra-marital births among fi rst births was 74 % in 2009, and among second and further births it was still far above 40 %. The difference between the age at the fi rst birth in the life of the woman and the age at the fi rst birth in the current marriage was 2.3 years. Between second and further births, the age difference was 0.9 and 0.8 years, respectively. Furthermore, 20 % of the women had already given birth before the fi rst child in the current marriage was born. The proportion of extra-marital births in the new Federal Länder in the period between 1998 and 2002 was more than twice as high as in the West, and it increased more rapidly: from 47 % in 1998 to 55 % in 2002. Table 1 summarizes the data sources used. As far as we know, these contain the only data existing for the German population which provide the subdivision of births into fi rst births (parity 1), second births (parity 2), third births (parity 3) and higher-order births (parity 4+) for the years 1955 to 2008. Since the case numbers in the data sources used differ from the total number of births registered in Western and Eastern Germany, the relative parity-specifi c subdivision of births, calculated from the data sources, was applied to the total number of births in Western and Eastern Germany as published by the statistical offi ce. In formal terms, the age- and parity-specifi c numbers of births B(x)i were estimated as follows: with B(x) denoting the offi cial overall number of births of x-year-old women, and B‘(x)i and B‘(x), respectively, denoting the number of births of parity i of x-year-old women as well as the corresponding total number of births included in the respec- tive data source. From these age- and parity-specifi c birth numbers and from the numbers of living women aged 15 to 49 published by the statistical offi ce, it was possible to derive age- and parity-specifi c fertility rates for single ages of the moth- ers which fi nally enabled us to estimate the parity-specifi c TFRi from equation (2) as well as the parity-specifi c age at childbirth MABi from equation (8). The tempo-ad- justed total fertility rates TFR* were fi nally calculated as shown in equation (9). For parities 1, 2 and 3 we used the tempo-adjusted TFR1*, TFR2* and TFR3* (calculated (x)B' (x)B' B(x)B(x) ii (10) • Marc Luy, Olga Pötzsch614 with equation 6), whereas for parity 4+ we used the conventional TFR4+ as recom- mended by Sobotka (2004a) in order to reduce random fl uctuations. 3 Results In a fi rst step, we subdivided the total number of births by the age of the mother for Western and Eastern Germany published by the Statistical Offi ce of Germany into the parities on the basis of the parity distributions reconstructed from the various data sources. From these parity-specifi c birth numbers, we decomposed the con- Tab. 1: Data sources used to estimate age- and parity-specifi c fertility rates (a) Western Germany (former Federal Republic of Germany/old Federal Länder) Data source Period used Basis of the parity-specific subdivision of births Birg et al. (1990) 1958 - 1985 Marital and extra-marital births from the sample of the project entitled “Labour market dynamics, family development and generative conduct”, ages 15-49 Kreyenfeld (2002) 1985 - 1995 Extra-marital births from the sample of the SOEP, marital births from official statistics, ages 15-45 Perinatal data 1995 - 1999 Births recorded in the perinatal survey in Western Germany without the Baden- Württemberg and West Berlin, ages 15-49 Official birth statistics 1998 - 2002 Births from the current marriage (without West Berlin from 2001 on), ages 15-49 Kreyenfeld et al. (2010) 2001 - 2008 Births recorded in the perinatal survey in Western Germany without West Berlin, ages 15-44 Official birth statistics 2009 All births (without West Berlin), ages 15-49 (b) Eastern Germany (former GDR/new Federal Länder) Data source Period used Basis of the parity-specific subdivision of births Official birth statistics of the GDR 1954 - 1988 All births, ages 15-45 Perinatal data 1995 - 2000 Births recorded in the perinatal survey in Eastern Germany without East Berlin, ages 15-49 Kreyenfeld et al. (2010) 2001 - 2008 Births recorded in the perinatal survey in Eastern Germany including West Berlin, ages 15-44 Official birth statistics 2009 All births (without East Berlin), ages 15-49 Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 615 ventional total fertility rate TFR – as described in the previous section – into parities 1, 2, 3 and 4+. The corresponding estimates for TFR1, TFR2, TFR3 and TFR4+ for each calendar year can be found in Annex 1. Figure 1 shows the proportions of the parity-specifi c TFRi from 1958 to 2008 cal- culated from these data. Although the time trends of the parity-specifi c proportions of the TFR reveal interesting differences between Western and Eastern Germany, both parts of the country resemble each other in the fact that total fertility is mainly determined by parities 1 and 2. All in all, fi rst and second born children account for 70 % (from the end of the 1950s until the 1960s) to 80-85 % (since the 1970s in East- ern Germany and since the 1980s in Western Germany) of the total number of live births in the analyzed period. The proportions of parity 3 remain largely constant in both Western and Eastern Germany, whilst births of fourth and higher order have clearly become less signifi cant since the 1970s in both parts of Germany and are of only minor signifi cance for total fertility. With regard to the tempo effect component in the conventional TFR it is therefore of primary relevance how the average age at childbirth of mothers of fi rst and second children has changed in the analyzed calendar years. Fig. 1: Proportions of parity-specifi c TFRis in the conventional total fertility rate TFR in Western and Eastern Germany, 1958-2008 (a) Western Germany (b) Eastern Germany 0 10 20 30 40 50 60 70 80 90 100 1958 1968 1978 1988 1998 2008 P ro p o rt io n o f th e to ta l T F R in % Calendar year Parity 4+ Parity 3 Parity 2 Parity 1 0 10 20 30 40 50 60 70 80 90 100 1958 1968 1978 1988 1998 2008 P ro p o rt io n o f th e to ta l T F R in % Calendar year Parity 1 Parity 2 Parity 3 Par. 4+ Notes: Data basis of the estimates for Western Germany for the years 1958-1985 Birg et al. (1990), 1986-1995 Kreyenfeld (2002), 1996-1999 perinatal survey, 2000 offi cial statistics (marital births), 2001-2008 Kreyenfeld et al. (2010); data basis of the estimates for Eastern Germany for the years 1954-1988 offi cial statistics of the GDR, 1995-2000 perinatal survey, 2001-2008 Kreyenfeld et al. (2010); the missing calendar years 1989-1994 for Eastern Ger- many were estimated by means of linear interpolation of the values for 1988 and 1995; the parity-specifi c TFRi for single calendar years can be found in Annex 1. • Marc Luy, Olga Pötzsch616 Figures 2a to 2d present the annual changes in the average parity-specifi c age at childbirth ri for the same observation period estimated from the age- and parity- specifi c numbers of births. The values for parity 1 in Western Germany (black dots in Fig. 2a) are to be found exclusively in the negative range until the beginning of the 1970s. This means that the average age of women giving birth for the fi rst time is continuously decreased during these years. The situation is similar for the aver- age age at childbirth of parities 2 (shown in Fig. 2a by white triangles) and 3 (star signature in Fig. 2c). Consequently, one can presume that tempo effects increased the conventional TFR in the years of the baby boom. The changes in the average age of the mothers of children of fourth and higher order (grey squares in Fig. 2c) show a trend in contrast to parities 1 and 2 between the mid-1960s and the beginning of the 1970s. Because of the minor signifi cance of parity 4+ for total fertility, this can only result in a slight reduction of the tempo effects caused by parities 1, 2 and 3. From the 1970s to the end of the 1990s, all parities show an almost permanent annual increase in the average age at childbirth in Western Germany, albeit with varying intensities. Above all in parity 1, the annual changes are more than 0.1 years in most calendar years, with the maximum value of 0.26 being reached in 1983. Only in the second half of the 1980s the values for r1 are around zero. Since the early 1990s, there is a rise in the annual increase again, with an overall upward trend until the last year of observation. The changes in the other parities are very similar over the entire period. In the last years of the observation period, the annual change in the average age at childbirth among parities 1 to 3 is between 0.15 and 0.20 years, so that the TFR in Western Germany was infl uenced most by tempo effects in the 1970s and early 1980s as well as since the early 1990s. In Eastern Germany, the values for ri of all parities fl uctuate around zero from the mid-1960s until the end of the 1980s (see Figs. 2b and 2d). The few exceptions relate to parities 2, 3 and 4+ for a short time around 1970 and to parity 4+ at the end of the 1970s and at the beginning of the 1980s. All in all, the conventional TFR in Eastern Germany should be more or less unaffected by tempo effects in this period. Since unifi cation, the trends have changed considerably. Unfortunately, for the years be- tween 1987 and 1996 the change in the average age at childbirth cannot be esti- mated. However, the ri values derived for the years from 1996 to 2000 are – above all for parities 1 and 2 – very high and much higher than in Western Germany. The dashed interpolated lines in Figures 2b and 2d between 1987 and 1996 are included to provide an impression of the massive changes which occurred in the ages at childbirth among Eastern German mothers during the 1990s. These lines cannot be used to estimate the ri values for the single years of this period, which could indeed have been rather above the level of 1996 particularly in the fi rst half of the 1990s. However, they indicate that the extremely low TFR of Eastern Germany in this pe- riod is caused to a considerable degree by tempo effects. From the beginning of the 20th century on the annual change in the average age at childbirth returns to a level of around 0.2 years among parities 1 and 2, and is hence similar to the West German level. The fl uctuations are larger in parities 3 and 4+ with many of the single values being around zero. However, as can be seen in Figure 1b, the changes in the ages at Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 617 Fig. 2: Annual changes in the average parity-specifi c age at childbirth ri in Western and Eastern Germany, 1958-2008 (a) parities 1 and 2, Western Germany (b) parities 1 and 2, Eastern Germany (c) parities 3 and 4+, Western Germany (d) parities 3 and 4+, Eastern Germany -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 0,4 1958 1968 1978 1988 1998 2008 C ha ng e in y ea rs Calendar year Parity 1 Parity 2 -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 0,4 1958 1968 1978 1988 1998 2008 C ha ng e in y ea rs Calendar year Parity 3 Parity 4+ -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 0,4 1958 1968 1978 1988 1998 2008 C ha ng e in y ea rs Calendar year Parity 3 Parity 4+ -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 0,4 1958 1968 1978 1988 1998 2008 C ha ng e in y ea rs Calendar year Parity 1 Parity 2 Notes: Data basis of the estimates for Western Germany for the years 1959-1984 Birg et al. (1990), 1985 combination Birg et al. (1990)/Kreyenfeld (2002), 1986-1994 Kreyenfeld (2002), 1995 combination Kreyenfeld (2002)/perinatal survey, 1996-1998 perinatal survey, 1999-2001 offi cial statistics (marital births), 2002-2007 Kreyenfeld et al. (2010), 2008 com- bination Kreyenfeld et al. (2010)/offi cial statistics (all births); data basis of the estimates for Eastern Germany for the years 1958-1987 offi cial statistics of the GDR, 1996-1999 perinatal survey, 2000-2001 combination perinatal survey/Kreyenfeld et al. (2010), 2002-2007 Krey- enfeld et al. (2010), 2008 combination Kreyenfeld et al. (2010)/offi cial statistics (all births). • Marc Luy, Olga Pötzsch618 childbirth of the mothers of third and further children have only a minor infl uence on the magnitude of the tempo effects. The estimated annual changes in the parity-specifi c age at childbirth can be used to adjust the TFRis for tempo effects according to the method proposed by Bon- gaarts and Feeney (1998), and the resulting TFRi*s can then be cumulated to the tempo-adjusted total fertility rate TFR* (the values for the TFRi* and the total TFR* can be found for the single calendar years in Annex 2). Figure 3 shows the corre- sponding estimates for Western Germany in comparison to the conventional TFR (thin line). All in all, the estimates for the tempo-adjusted TFR* derived from the various data sources (designated in Fig. 3 by different symbols) show a coherent overall trend. Since tempo adjustment with the method of Bongaarts and Feeney (1998) can generally lead to distinct annual fl uctuations (and here additionally the combination of different data sources), more robust results are obtained when averaging the tempo-adjusted TFR* for three calendar years (see Goldstein et al. 2009). The result- ing estimates for the TFR* of Western Germany can be found in Table 2a. The thick black line in Fig. 3 represents the corresponding trend of the TFR* which refl ects the expectations that have already been outlined in connection with the trends in the annual changes in parity-specifi c ages at childbirth. The TFR* is slightly below the conventional TFR from the late 1950s to the mid-1960s because the age at child- birth was falling at that time. This shows that the increase in the TFR at the begin- ning of the baby boom in the 1950s was not only caused by the actual increase in fertility but also to a slight degree by tempo effects. Similar results were shown for instance for the USA (Bongaarts/Feeney 1998). At the end of the 1960s and at the beginning of the 1970s, practically no differences can be found between the TFR and the TFR*. Since the early 1970s, the TFR* in Western Germany has been higher than the conventional TFR. Whilst the TFR stagnated between 1.3 and 1.4 after the fertility decline between the second half of the 1960s and the mid-1970s, the TFR* declined less in the 1970s, and at the beginning of the 1980s the TFR* increased slightly to about 1.7. The following years show a subsequent decrease in the TFR* that persist- ed until 1990. Since then, the tempo-adjusted total fertility rate shows a more or less continuous increase, reaching almost 1.7 in the last year of the observation period (2008). All in all, although the TFR* is far from the replacement level of 2.1 children per woman (upper dashed line in Fig. 3), it lies – in contrast to the conventional TFR – clearly above the level of “lowest-low fertility”, which Kohler et al. (2002) defi ned as 1.3 children per woman (lower dashed line in Fig. 3). The differences between the conventional TFR and the tempo-adjusted TFR* also correspond to the expectations for Eastern Germany outlined above on the ba- sis of the estimated annual changes in the average parity-specifi c age at childbirth. In Figure 4 the corresponding estimates are, again displayed for the single years and the trend in the three-year average of the TFR* (the respective values can be found in Tab. 2b, as well as in Annex 2). It can be seen that tempo effects also led to a slight increase in the total fertility rate during the 1950s in Eastern Germany which is indicated by the somewhat lower values of the TFR* in comparison to the TFR. Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 619 In the subsequent years until the mid-1980s, the annual changes in the mothers’ average age at childbirth were too small to lead to signifi cant tempo effects. Con- sequently, there are virtually no differences between the TFR and the TFR* in this period. This changes in the last years prior to reunifi cation during which the TFR* in Eastern Germany rises in contrast to the decreasing TFR because of the increasing age at childbirth, similar to what can be observed for Western Germany at the end of the 1970s. Although we have only few estimates for the TFR* in the 1990s because of the available data sources, these estimates illustrate to what degree the conventional TFR (and the actual birth numbers) were affected by changes in the mean age at childbirth in Eastern Germany. Whereas the conventional TFR was only 1.04 in 1997, the estimated tempo-adjusted TFR* is 1.47. Equally to what has been done in Fig- Fig. 3: Estimates of the tempo-adjusted total fertility rate TFR* in Western Germany from various data sources, 1950-2010 0,0 0,5 1,0 1,5 2,0 2,5 3,0 1950 1960 1970 1980 1990 2000 2010 T ot al f er til ity ra te Calendar year TFR TFR* (Bg) TFR* (Bg/Kr1) TFR* (Kr1) TFR* (Kr1/AS1) TFR* (PE) TFR* (AS1) TFR* (Kr2) TFR*(Kr2/AS2) TFR* Notes: The abbreviations in brackets refer to the data basis for the estimate of the TFR*, Bg = Birg et al. (1990), Kr1 = Kreyenfeld (2002), Kr2 = Kreyenfeld et al. (2010), PE = perinatal survey, AS1 = offi cial statistics (marital births), Bg/Kr1 = combination Birg et al. (1990)/Kreyenfeld (2002), Kr1/PE = combination Kreyenfeld (2002)/perinatal survey, Kr2/ AS2 = combination Kreyenfeld et al. (2010)/offi cial statistics (all births); the trend line of the TFR* is calculated from a three-year moving average (values for the mid-calendar years can be found in Tab. 2); the parity-specifi c TFRi*s for the single calendar years can be found in Annex 2. • Marc Luy, Olga Pötzsch620 ure 2b, the dashed sections of the line for the tempo-adjusted TFR* in Figure 4 are only included to give an impression of the fertility conditions prevailing in the fi rst half of the 1990s. In fact, the TFR* could have also been below this line during these years as indicated by the estimate for the single year 1996. From 1997 to 2005, the tempo adjusted TFR* ranged relatively constant around 1.5. Whether the increase in the TFR* in the last years of the observation period as indicated by the estimates from 2006 onwards refl ects an actual trend can only be said once the data for the next years become available. Tab. 2: Estimates of the tempo-adjusted total fertility rate TFR* in Western and Eastern Germany, 1950-2010 (three-years averages) (a) Western Germany 1950-1959 1960-1969 1970-1979 1980-1989 1990-1999 2000-2009 Year TFR* Year TFR* Year TFR* Year TFR* Year TFR* Year TFR* 1950 -- 1960 2.18 1970 2.03 1980 1.60 1990 1.47 2000 1.54 1951 -- 1961 2.19 1971 1.92 1981 1.66 1991 1.48 2001 1.56 1952 -- 1962 2.25 1972 1.82 1982 1.68 1992 1.49 2002 1.58 1953 -- 1963 2.30 1973 1.71 1983 1.65 1993 1.51 2003 1.60 1954 -- 1964 2.33 1974 1.63 1984 1.61 1994 1.51 2004 1.60 1955 -- 1965 2.33 1975 1.61 1985 1.57 1995 1.52 2005 1.61 1956 -- 1966 2.34 1976 1.59 1986 1.55 1996 1.56 2006 1.64 1957 -- 1967 2.36 1977 1.57 1987 1.51 1997 1.58 2007 1.67 1958 -- 1968 2.31 1978 1.54 1988 1.48 1998 1.56 2008 -- 1959 -- 1969 2.17 1979 1.55 1989 1.48 1999 1.53 2009 -- (b) Eastern Germany 1950-1959 1960-1969 1970-1979 1980-1989 1990-1999 2000-2009 Year TFR* Year TFR* Year TFR* Year TFR* Year TFR* Year TFR* 1950 -- 1960 2.18 1970 2.23 1980 1.83 1990 -- 2000 1.53 1951 -- 1961 2.24 1971 2.11 1981 1.86 1991 -- 2001 1.53 1952 -- 1962 2.31 1972 1.91 1982 1.85 1992 -- 2002 1.53 1953 -- 1963 2.35 1973 1.69 1983 1.81 1993 -- 2003 1.54 1954 -- 1964 2.37 1974 1.58 1984 1.79 1994 -- 2004 1.52 1955 -- 1965 2.35 1975 1.59 1985 1.81 1995 -- 2005 1.53 1956 2.12 1966 2.32 1976 1.68 1986 1.87 1996 -- 2006 1.60 1957 2.07 1967 2.29 1977 1.77 1987 -- 1997 1.47 2007 1.65 1958 2.09 1968 2.26 1978 1.81 1988 -- 1998 1.50 2008 -- 1959 2.12 1969 2.24 1979 1.82 1989 -- 1999 1.52 2009 -- Notes: -- no estimates available; values for the TFR* calculated from the three-year mov- ing average of the estimates for the single calendar years (see Annex 2). Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 621 A direct East-West comparison of fertility trends in Germany is presented in Fig- ure 5 according to the conventional TFR and the tempo-adjusted TFR*. The trends in the conventional TFR can be found in Figure 5a and the trends in the tempo- adjusted TFR* can be found in Figure 5b. Interestingly, both variants of calculation show the same phases in which the total fertility rate is higher in Eastern or Western Germany. However, the differences in the tempo-adjusted TFR* in the two parts of Germany are smaller in each phase (and since the second half of the 1990s almost negligible). (Note once more that the dashed sections in the line of the TFR* for Eastern Germany are no real estimates, but represent the interpolated connection between the estimates for 1986 and 1997.) Besides this, the graphical West-East comparison of the total fertility rate by means of the two calculation variants pro- vides one more important result: fertility had virtually disappeared at the end of the Fig. 4: Estimates of the tempo-adjusted total fertility rate TFR* in Eastern Germany from various data sources, 1950-2010 0,0 0,5 1,0 1,5 2,0 2,5 3,0 1950 1960 1970 1980 1990 2000 2010 T ot al f er til ity ra te Calendar year TFR TFR* (AS3) TFR* (PE) TFR* (PE/Kr2) TFR* (Kr2) TFR* (Kr2/AS2) TFR* Notes: The abbreviations in brackets refer to the data basis for the estimate of the TFR*, AS3 = offi cial statistics (GDR), PE = perinatal survey, Kr2 = Kreyenfeld et al. (2010), PE/Kr2 = combination perinatal survey/Kreyenfeld et al. (2010), Kr2/AS2 = combination Kreyen- feld et al. (2010)/offi cial statistics (all births); the trend line of the TFR* is calculated from the three-year moving average (values for the mid calendar years can be found in Tab. 2); for the calendar years 1987-1996, the trend for the TFR* in Eastern Germany (years without estimate) was completed by linear interpolation of the values for 1986 and 1997 (dashed line); the parity-specifi c TFRi*s for the single calendar years can be found in An- nex 2. • Marc Luy, Olga Pötzsch622 observation period. This holds for both versions of the total fertility rate, namely the conventional TFR and the tempo-adjusted TFR*. Finally, Figure 6 (Western Germany) and Figure 7 (Eastern Germany) show the trends in the TFR as well as in the TFR* in comparison to three other western and eastern European populations for which the corresponding values could be calcu- lated from the Human Fertility Database (HFD) (the TFR* for these populations was calculated analogously to our estimates for Western and Eastern Germany, i.e. us- ing the tempo-adjusted TFRi* for parities 1, 2 and 3 and the conventional TFRi for the higher parities, presented by means of three-year moving averages). Equally to what has been done in Figure 5, the graphs on the left-hand side show the conven- tional TFR and the graphs on the right-hand side show the tempo-adjusted TFR*. The fi gures are intended to enable us to evaluate the degree to which our estimates of the TFR* for Western and Eastern Germany derived from data sources of differ- ent quality can be regarded as plausible. It can be assumed that populations with comparable demographic conditions and trends also show similar trends in tempo effects. This, however, is a more intuitive concept rather than real empirical evi- dence, More so if one takes into consideration that despite the common features Fig. 5: Total fertility rate in Western and Eastern Germany according to the conventional TFR and the tempo-adjusted TFR*, 1950-2010 (a) conventional TFR (b) tempo-adjusted TFR* 0,0 0,5 1,0 1,5 2,0 2,5 3,0 1950 1960 1970 1980 1990 2000 2010 To ta l f er til ity ra te Calendar year Western Germany Eastern Germany 0,0 0,5 1,0 1,5 2,0 2,5 3,0 1950 1960 1970 1980 1990 2000 2010 To ta l f er til ity ra te Calendar year Western Germany Eastern Germany Notes: Values for the tempo-adjusted TFR* from the three-year moving average of the estimates for the single calendar years (see Tab. 2); for the calendar years 1987-1996, the trend for the TFR* in Eastern Germany (years without estimate) was completed by linear interpolation of the values for 1986 and 1997 (dashed line). Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 623 there are also historic and socio-structural differences between the two populations under consideration. The trends of the conventional TFR in Western Germany, Austria, the Netherlands and Sweden shown in Figure 6a refl ect the already known fact that the West Ger- man fertility level is located at the low end of the range in other western European populations. Austria is comparable to Western Germany with regard to the level and trend of the TFR since the 1980s (the HFD provides data for Austria only since this time). In Sweden and in the Netherlands, the TFR has increased in the last ten years, in contrast to the stagnation observed in Western Germany and Austria, where it ranges around the level of 1.8 to 1.9 in most recent years. Figure 6b reveals that the estimates for the TFR* of Western Germany are also close to the correspond- ing values of Austria, for which age- and parity-specifi c birth numbers of the total population are published directly by the national statistical offi ce (Statistik Austria). This fi nding holds for the mid-1990s onwards. In the years before, at around 1990, the Austrian TFR* shows a strong fl uctuation which is not visible in the conventional TFR. All in all, the estimates for the TFR* of Western Germany fi t well and plausible into the picture of the Western European populations. Only in the 1980s and early Fig. 6: Total fertility rate in Western Germany in comparison to other Western European populations according to the conventional TFR and the tempo-adjusted TFR*, 1950-2010 (a) conventional TFR (b) tempo-adjusted TFR* 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 1950 1960 1970 1980 1990 2000 2010 To ta l f er til ity ra te Calendar year GER West AUT NED SWE 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 1950 1960 1970 1980 1990 2000 2010 To ta l f er til ity ra te Calendar year GER West AUT NED SWE Notes: Values for the tempo-adjusted TFR* for Western Germany (GER West) refl ect the three-year moving average of the estimates for the single calendar years (see Tab. 2); val- ues for Austria (AUT), the Netherlands (NED) and Sweden (SWE) calculated with data from the Human Fertility Database (HFD), three-year moving averages. • Marc Luy, Olga Pötzsch624 1990s the estimates for the TFR* seem somewhat too low. An interesting result is that in the most recent years the differences in the total fertility rate between West- ern Germany and Austria, on the one hand, and Sweden and the Netherlands, on the other, are much smaller when the TFR is tempo adjusted. Figure 7 also includes one population which seems suitable for comparison with Eastern Germany in order to judge the plausibility of our tempo-adjusted estimates. Roughly since 1980, Slovenia shows a similar trend in the conventional TFR com- pared to that of Eastern Germany. In the 1990s, however, both differ when no fer- tility changes comparable to those in Eastern Germany occurred in Slovenia (see Fig. 7a). The two other populations, from the Czech and Slovak Republics, exhibit a much higher TFR until the mid-1990s, but show similar changes in the fertility level as the East German population in the fi rst half of the 1990s (albeit without recovery after the baby bust). The comparison of the estimates for the East German tempo- adjusted TFR* with the corresponding fi gures for the three other populations in Figure 7b also shows that the estimates for Eastern Germany seem highly plausible. Fig. 7: Total fertility rate in Eastern Germany in comparison to other eastern European populations according to the conventional TFR and the tempo-adjusted TFR*, 1950-2010 (a) conventional TFR (b) tempo-adjusted TFR* 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 1950 1960 1970 1980 1990 2000 2010 To ta l f er til ity ra te Calendar year GER East CZE SVK SVN 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 1950 1960 1970 1980 1990 2000 2010 To ta l f er til ity ra te Calendar year GER East CZE SVK SVN Notes: Values for the tempo-adjusted TFR* for Eastern Germany (GER East) refl ect the three-year moving average of the estimates for the single calendar years (see Tab. 2); the trend for the TFR* in Eastern Germany for the calendar years 1987-1996 (years with no estimate) was completed by linear interpolation of the values for 1986 and 1997 (dashed lines); values for the Czech Republic (CZE), the Slovak Republic (SVK) and Slovenia (SVN) are calculated with data from the Human Fertility Database (HFD), three-year moving aver- ages. Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 625 There are only minor differences in comparison to the values for Slovenia in the 1980s as well as since the beginning of the 21st century. During the 1990s, the much less pronounced fertility reduction shown by the TFR* in comparison to the con- ventional TFR fi ts the examples of the Czech and Slovak Republics very well. Both experienced declines in the conventional TFR similar to those occurring in Eastern Germany during this period. 4 Discussion As already mentioned in the introduction, the main aim of the work for this article was the compilation of a time series of estimates for the tempo-adjusted total fer- tility rate in Western and Eastern Germany. To achieve this, we used a variety of data sources from which age- and parity-specifi c birth numbers could be derived to serve as basis for estimating the tempo-adjusted TFR*. It was possible to construct a complete time series for Western Germany for the years from 1960 to 2007. For Eastern Germany, however, it was not possible to provide such a complete time series. We were able to present estimates (by means of three year averages) for the years 1956 to 1986 and for 1997 to 2007 (the estimates for single calendar years cover the years 1959-2008 for Western Germany and the years 1955-1987 as well as 1996-2008 for Eastern Germany). Although the idea behind Bongaarts and Feeney’s tempo approach (not only for fertility but also for all other demographic events) as well as the arguments of the critics are described in Luy (2010), we should add a few remarks with regard to the interpretation and correct attribution of the tempo-adjusted time series presented in this paper. Particularly the question of the interpretation of the tempo-adjusted total fertility rate is not easy to answer, and has already led to a number of misun- derstandings in the corresponding demographic literature. The advantage of the conventional TFR is its clear defi nition and interpretation as the sum of the age-spe- cifi c fertility rates observed in a given calendar year. In order to explain the meaning of the TFR* as intended by Bongaarts and Feeney, it is necessary to describe this indicator in a broader context. Independent of the calculation variant (conventional or tempo-adjusted), the aim of the calculation of the total fertility rate for a period is to provide a cross-sectional measure of a population’s current fertility. Therefore, only women who are aged between 15 and 49 in the calendar year under observation, i.e. women hence be- longing to 35 different cohorts, are considered. The current fertility of these women is infl uenced to differing degrees by the current political and societal framework and their own reproduction histories. In order to obtain a better understanding of a period measure, one might imagine that the current age-specifi c fertility conditions are used to construct a scenario for a hypothetical population. All the women of this hypothetical population would realise precisely the given age-specifi c fertility at any time. In such a scenario, all female cohorts would have the same fi nal aver- age number of children, which equals the average number of children of all women • Marc Luy, Olga Pötzsch626 aged between 15 and 49 living in each calendar year. Demographers refer to such a scenario as a “stable population”. A real population whose current fertility is to be characterised by the total fertil- ity rate is naturally never stable. Consequently, period indicators derived in the logic of the stable population always have to be regarded as purely hypothetical. The idea behind Bongaarts and Feeney’s tempo approach is based on the fact that the number of births and the number of women aged between 15 to 49 living in a spe- cifi c calendar year do not originate from a stable population. Imagine a rather simple exemplary case in which each woman has exactly one child, gives birth at exactly the same age, and that the times of the births are evenly distributed over the year. In this scenario, the sum of the age-specifi c fertility rates as an indicator of the current fertility would also be exactly one child per woman in any given calendar year. If, however, the age at which the women give birth to their child continually increases (so that a change in birth timing takes place, but not in birth quantum), the cohorts of women being in reproductive ages in a calendar year would have their children over a longer period than one year. In this case, all women living in a specifi c calen- dar year would still realise one birth during their lives, but the average value derived from the age-specifi c fertility rates for this year would be lower than one. Bongaarts and Feeneys’ approach for characterising the fertility of a specifi c cal- endar year takes into account that the current fertility of a real population does not originate from a situation in which the age at childbirth of all cohorts currently living remains unchanged. The idea is hence to adjust the time frames of the birth times of the newborns and of the cohorts of mothers (i.e. the numerators and denomina- tors of the age-specifi c fertility rates) to capture the current birth quantum of the currently living women. The adjustment relates exclusively to the above described expansion effect of the birth period resulting from the increase in the age at child- birth, assuming that the fertility quantum remains unchanged despite the age shift (analogously, when the age at childbirth declines, the reduction effect of the shorter childbirth period would be adjusted for). In a stable population, the total fertility rate of a calendar year can be regarded as the average number of children born during the life course of all female cohorts currently living. In these terms, the conventional period TFR (i.e. the observed to- tal fertility rate of a specifi c calendar year) can also be interpreted as the average number of children born by the female cohorts living at the same time in the hypo- thetical population in the course of their reproductive life span. The prerequisite is that these female cohorts realise exactly the age-specifi c fertility rates observed in the period, i.e. without changes in birth quantum and birth timing. The tempo-ad- justed TFR* is to be equivalently interpreted as the average number of children who are born to the hypothetical female cohorts living at the same time in the course of their reproductive life span if these female cohorts realise the birth quantum of the period observed, defi ned by the age-specifi c fertility rates, but with changes in birth timing. When we reduce the interpretation to the single hypothetical cohort usually used, then the TFR* does not refl ect the age-specifi c fertility rates observed in the period, but the age-specifi c fertility rates adjusted for changes in the birth timing during the observed year (see also Lesthaeghe/Willems 1999). Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 627 Besides the aspects of birth quantum and birth timing, the age distribution of the parity-specifi c fertility rates by the age of the women is also relevant with regard to the tempo adjustment according to the Bongaarts and Feeney formula used in this article. It becomes evident from equation (6) that the tempo adjustment is ex- clusively based on the change in the average age at childbirth of the parities. Thus, the Bongaarts and Feeney formula implies that the distribution of the age-specifi c fertility rates remains constant when shifting with age. Most of the methodical crit- ics of tempo adjustment focus on this feature of the Bongaarts and Feeney method (see e.g. van Imhoff/Keilman 2000; Kohler/Philipov 2001; van Imhoff 2001; Yi/Land 2001). In real populations, the changes in the average age at childbirth are indeed accompanied by variance changes which also exert an infl uence on the number of children born in a calendar year. Thus, the increase in the average age at childbirth can be caused by both an increase in age-specifi c fertility in the higher reproductive age and by a fall in the fertility rates among younger women (in the fi rst case, the fertility quantum would increase in the long term; in the latter it would fall). Conse- quently, very different changes in the age distribution of the parity-specifi c fertility rates can lead to identical changes in the average age at childbirth, and hence to an identical tempo adjustment with the Bongaarts and Feeney formula. Such cases are not rare and can also be observed in the German population during the calendar years analysed in this paper. Theoretically it is possible to extend the tempo adjustment to include the effect of changes in the age distribution of the parity-specifi c fertility rates as proposed by Kohler and Philipov (2001). In practice, however, feasibility reaches its limit here in most cases because of the detailed nature of the data required. It is therefore important to note that the tempo adjustment with the Bongaarts and Feeney for- mula is merely an approximation of the intended adjustment of the total fertility rate (see Luy 2010 for details). However, the criticism of the non-consideration of variance effects can be countered by two arguments: The fi rst concerns the relative signifi cance of changes in the average age at childbirth and in the age distribution of the age-specifi c fertility rates for the numbers of births occurring in a specifi c calendar year. As Dinkel (1989) has shown by simulations, changes in the average age at childbirth have a much larger impact on the birth numbers than changes in the variance of the fertility distribution. It is not likely that the non-consideration of variance changes leading to an incorrect direction of the tempo adjustment with the Bongaarts and Feeney formula occurs frequently, albeit its absolute extent can indeed be distorted. The second argument is that the conventional TFR does not at all account for changes in birth timing. Consequently, also Kohler and Philipov (2001) concluded that an adjustment of the total fertility rate with the Bongaarts and Feeney formula is better for the analysis of period fertility than completely exclud- ing tempo adjustment. This discussion, however, is not aimed to ascertain which measure is better suited to characterise period fertility. One should not forget that the TFR and the TFR* are both pure period indicators, and hence both solely refl ect hypothetical average birth numbers. In case of the conventional TFR, this hypothetical average birth number is based on the observed fertility rates of a calendar year, and in the • Marc Luy, Olga Pötzsch628 case of the tempo-adjusted TFR* on the estimated birth quantum of the women liv- ing in this calendar year. The latter cannot be measured, but only modelled, which is certainly a weakness of the TFR* compared to the conventional total fertility rate. Ultimately, the two indicators are based on somewhat different reference quanti- ties. For the analysis of period fertility it is thus most informative to use them par- allel and supplementing one another, as it was done in all the papers listed in the introduction. Regarding the empirical results presented in this article, it can be stated that the two fertility indicators – the conventional TFR and the tempo-adjusted TFR* – identify different phases in fertility trends in Western and Eastern Germany. In both parts of the country, the TFR* is lower than the TFR until the end of the 1960s. This is a consequence of the decline in the average age at childbirth, in particular with regard to the fi rst and second births. The age of the women at the birth of their chil- dren rises markedly in Western Germany in the 1970s and 1980s. As a consequence, the tempo-adjusted TFR* is on average almost 0.18 higher than the conventional TFR during the years from 1971 to 1987. In the former GDR, by contrast, the age at childbirth remained relatively constant in this period, so that the tempo-adjusted TFR* and the conventional TFR do not differ signifi cantly. Since the beginning of the 1990s, the average age at childbirth of Western German women rises once more after a brief phase of relative stability. This trend causes an increasing deviation be- tween the estimated TFR* and the conventional TFR in Western Germany. In Eastern Germany, we can only presume that the difference between the two indicators was particularly large in the fi rst half of the 1990s. This is suggested by several indica- tors pointing towards a rapid increase in the age at childbirth of Eastern German mothers. An idea of the extent of this difference is provided by the estimates for the second half of the 1990s. The difference between the tempo-adjusted TFR* and the conventional TFR in the years 1997-1999 is between 0.37 and 0.43. In the years from 2000 to 2007, the TFR* in Eastern Germany is on average 0.28 higher than the conventional TFR. Hence, the combined picture of the conventional TFR and the tempo-adjusted TFR* provides interesting results with regard to the trends in period fertility in West- ern and Eastern Germany, which were not analysed in detail in this paper. This ap- plies above all to the West-East differences in the overall trend and the massive tempo effects in Eastern Germany during the 1990s. Since 2009 it is possible to analyse level and trends of fertility in Germany with tempo-adjusted fertility rates on the basis of parity-specifi c data for all births from offi cial statistics. For the period prior to this we have compiled the best possible estimates. Even if these estimates are not comparable with the data of offi cial statistics in qualitative terms, the data presented in this paper enables researchers to include the population of Western and Eastern Germany in future research on international trends in tempo-adjusted period fertility. 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In: Population and Development Review 26,3: 549-553. Witte, James C.; Wagner, Gert 1995: Declining fertility in East Germany after unifi cation: a demographic response to socioeconomic change. In: Population and Development Review 21,2: 387-397. Yi, Zeng; Land, Kenneth C. 2001: A sensitivity analysis of the Bongaarts-Feeney method for adjusting bias in observed period total fertility rates. In: Demography 38,1: 17-28. Translated from the original text by the Federal Institute for Population Research. The reviewed and authors’ authorised original article in German is available under the title “Schätzung der tem- pobereinigten Geburtenziffer für West- und Ostdeutschland, 1955-2008”, DOI 10.4232/10.CPoS- 2010-14de or URN urn:nbn:de:bib-cpos-2010-14de3, at http://www.comparativepopulationstud- ies.de. Date of submission: 20.12.2010 Date of acceptance: 26.12.2010 Dr. Marc Luy ( ). Vienna Institute of Demography of the Austrian Academy of Sciences, Wittgenstein Centre for Demography and Global Human Capital, A-1040 Vienna, Austria. E-Mail: mail@marcluy.eu URL: http://www.marcluy.eu Olga Pötzsch. Federal Statistical Office, Gustav-Stresemann-Ring 11, 65189 Wiesbaden, Germany. E-Mail: olga.poetzsch@destatis.de, URL: http://www.destatis.de Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 633 Annex 1: Estimated subdivision of the conventional total fertility rate TFR for Western and Eastern Germany into the parity-specifi c TFRis, 1954-2009 Western Germany Eastern Germany Year TFR1 TFR2 TFR3 TFR4+ TFR TFR1 TFR2 TFR3 TFR4+ TFR 1954 -- -- -- -- 2.10 0.93 0.71 0.36 0.35 2.35 1955 -- -- -- -- 2.11 0.93 0.71 0.37 0.35 2.35 1956 -- -- -- -- 2.20 0.88 0.68 0.37 0.36 2.26 1957 -- -- -- -- 2.30 0.85 0.66 0.36 0.36 2.21 1958 0.94 0.67 0.37 0.31 2.29 0.85 0.65 0.36 0.37 2.21 1959 0.97 0.69 0.39 0.33 2.37 0.89 0.67 0.38 0.41 2.35 1960 0.97 0.69 0.38 0.32 2.37 0.90 0.65 0.37 0.41 2.33 1961 1.00 0.72 0.40 0.34 2.46 0.95 0.66 0.38 0.43 2.40 1962 1.00 0.71 0.39 0.34 2.44 0.97 0.66 0.36 0.43 2.42 1963 1.02 0.74 0.41 0.35 2.52 0.99 0.68 0.37 0.43 2.47 1964 1.02 0.75 0.41 0.35 2.54 0.99 0.69 0.37 0.44 2.51 1965 1.02 0.75 0.40 0.34 2.51 1.00 0.70 0.36 0.42 2.48 1966 1.04 0.75 0.41 0.33 2.53 0.98 0.70 0.36 0.38 2.42 1967 1.03 0.75 0.39 0.31 2.49 0.96 0.69 0.35 0.34 2.34 1968 0.99 0.72 0.37 0.29 2.38 0.95 0.69 0.34 0.31 2.30 1969 0.93 0.67 0.34 0.26 2.21 0.96 0.68 0.33 0.27 2.24 1970 0.88 0.61 0.30 0.22 2.02 0.98 0.67 0.30 0.24 2.19 1971 0.86 0.59 0.28 0.20 1.92 0.97 0.66 0.29 0.22 2.14 1972 0.78 0.53 0.24 0.17 1.71 0.90 0.54 0.19 0.14 1.79 1973 0.70 0.48 0.21 0.15 1.54 0.88 0.48 0.12 0.09 1.58 1974 0.70 0.48 0.19 0.13 1.51 0.87 0.48 0.11 0.08 1.54 1975 0.68 0.46 0.19 0.12 1.45 0.87 0.50 0.10 0.07 1.54 1976 0.68 0.47 0.18 0.11 1.45 0.90 0.55 0.11 0.07 1.64 1977 0.67 0.46 0.17 0.10 1.40 0.96 0.68 0.13 0.07 1.85 1978 0.66 0.46 0.17 0.09 1.38 0.99 0.70 0.14 0.07 1.90 1979 0.65 0.46 0.17 0.09 1.38 0.98 0.70 0.14 0.07 1.89 1980 0.69 0.48 0.18 0.09 1.44 1.01 0.70 0.16 0.07 1.94 1981 0.69 0.48 0.19 0.09 1.44 0.95 0.69 0.15 0.07 1.85 1982 0.68 0.47 0.18 0.08 1.41 0.93 0.70 0.16 0.07 1.86 1983 0.64 0.45 0.17 0.07 1.33 0.89 0.67 0.16 0.07 1.79 1984 0.61 0.44 0.17 0.07 1.29 0.85 0.65 0.16 0.07 1.74 1985 0.61 0.44 0.17 0.07 1.28 0.83 0.64 0.19 0.08 1.73 1986 0.66 0.48 0.15 0.06 1.35 0.81 0.63 0.18 0.08 1.70 1987 0.67 0.47 0.16 0.06 1.37 0.81 0.65 0.20 0.08 1.74 1988 0.69 0.49 0.17 0.07 1.41 0.78 0.62 0.19 0.08 1.67 1989 0.69 0.48 0.17 0.07 1.40 -- -- -- -- 1.57 1990 0.71 0.49 0.17 0.07 1.45 -- -- -- -- 1.52 1991 0.71 0.47 0.17 0.07 1.42 -- -- -- -- 0.98 1992 0.70 0.47 0.17 0.07 1.40 -- -- -- -- 0.83 1993 0.69 0.47 0.17 0.06 1.39 -- -- -- -- 0.77 • Marc Luy, Olga Pötzsch634 Notes: -- no estimates available; data basis of the estimates for Western Germany for the years 1958-1985 Birg et al. (1990), 1986-1995 Kreyenfeld (2002), 1996-1999 perinatal survey, 2000 offi cial statistics (marital births), 2001-2008 Kreyenfeld et al. (2010), 2009 of- fi cial statistics (all births); data basis of the estimates for Eastern Germany for the years 1954-1988 offi cial statistics of the GDR, 1995-2000 perinatal survey, 2001-2008 Kreyenfeld et al. (2010), 2009 offi cial statistics (all births); deviations between the sum of the parity- specifi c TFRi and the total TFR are caused by rounding errors. Western Germany Eastern Germany Year TFR1 TFR2 TFR3 TFR4+ TFR TFR1 TFR2 TFR3 TFR4+ TFR 1994 0.68 0.45 0.16 0.06 1.35 -- -- -- -- 0.77 1995 0.67 0.45 0.16 0.06 1.34 0.42 0.28 0.09 0.05 0.84 1996 0.66 0.50 0.17 0.08 1.40 0.49 0.31 0.09 0.06 0.95 1997 0.70 0.49 0.17 0.08 1.44 0.53 0.35 0.11 0.05 1.04 1998 0.69 0.49 0.16 0.07 1.41 0.58 0.35 0.11 0.05 1.09 1999 0.69 0.48 0.16 0.08 1.41 0.62 0.36 0.11 0.06 1.15 2000 0.68 0.51 0.16 0.06 1.41 0.66 0.38 0.11 0.06 1.21 2001 0.68 0.48 0.15 0.07 1.38 0.68 0.39 0.11 0.06 1.23 2002 0.68 0.47 0.15 0.07 1.37 0.69 0.40 0.11 0.05 1.24 2003 0.67 0.48 0.15 0.07 1.36 0.69 0.41 0.11 0.05 1.26 2004 0.67 0.48 0.16 0.07 1.37 0.71 0.42 0.12 0.06 1.31 2005 0.66 0.48 0.15 0.07 1.36 0.70 0.42 0.12 0.06 1.30 2006 0.65 0.47 0.16 0.07 1.34 0.69 0.43 0.13 0.06 1.30 2007 0.67 0.47 0.16 0.07 1.37 0.72 0.46 0.13 0.06 1.37 2008 0.67 0.47 0.16 0.07 1.37 0.73 0.47 0.14 0.07 1.40 2009 0.67 0.45 0.15 0.07 1.35 0.72 0.48 0.14 0.07 1.40 Annex 1 (continuation) Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany • 635 Annex 2: Estimated subdivision of the tempo-adjusted total fertility rate TFR* for Western and Eastern Germany into the parity-specifi c TFRi*s, 1954-2009 (annual values) Western Germany Eastern Germany Year TFR1* TFR2* TFR3* TFR4+* TFR* TFR1* TFR2* TFR3* TFR4+* TFR* 1954 -- -- -- -- -- -- -- -- -- -- 1955 -- -- -- -- -- 0.82 0.67 0.31 0.26 2.16 1956 -- -- -- -- -- 0.81 0.60 0.32 0.27 2.08 1957 -- -- -- -- -- 0.80 0.61 0.33 0.30 2.10 1958 -- -- -- -- -- 0.72 0.60 0.34 0.33 2.03 1959 0.86 0.64 0.37 0.30 2.19 0.75 0.61 0.37 0.38 2.15 1960 0.84 0.62 0.36 0.30 2.15 0.81 0.58 0.37 0.40 2.17 1961 0.87 0.63 0.36 0.33 2.20 0.87 0.56 0.36 0.43 2.23 1962 0.90 0.63 0.36 0.34 2.22 0.92 0.60 0.36 0.44 2.31 1963 0.92 0.68 0.38 0.36 2.32 0.94 0.66 0.36 0.47 2.40 1964 0.93 0.69 0.40 0.38 2.37 0.95 0.63 0.34 0.46 2.35 1965 0.92 0.66 0.38 0.35 2.30 0.97 0.63 0.32 0.40 2.35 1966 0.94 0.68 0.38 0.34 2.33 0.97 0.67 0.33 0.35 2.34 1967 0.96 0.71 0.40 0.35 2.38 0.96 0.65 0.32 0.33 2.27 1968 0.91 0.75 0.43 0.35 2.37 0.92 0.68 0.33 0.33 2.24 1969 0.84 0.71 0.38 0.30 2.19 0.91 0.71 0.36 0.33 2.26 1970 0.84 0.59 0.30 0.24 1.96 0.92 0.71 0.36 0.29 2.23 1971 0.91 0.57 0.27 0.20 1.95 0.93 0.73 0.34 0.29 2.21 1972 0.90 0.55 0.23 0.16 1.84 0.92 0.62 0.20 0.19 1.88 1973 0.84 0.49 0.18 0.12 1.66 0.90 0.52 0.12 0.11 1.63 1974 0.86 0.48 0.17 0.10 1.64 0.88 0.48 0.12 0.08 1.56 1975 0.80 0.49 0.18 0.10 1.59 0.89 0.49 0.10 0.06 1.55 1976 0.78 0.52 0.19 0.10 1.60 0.91 0.56 0.11 0.06 1.65 1977 0.77 0.52 0.17 0.09 1.56 0.91 0.71 0.13 0.07 1.82 1978 0.76 0.50 0.17 0.08 1.53 0.92 0.69 0.14 0.06 1.82 1979 0.73 0.50 0.19 0.09 1.51 0.92 0.64 0.15 0.06 1.78 1980 0.78 0.53 0.20 0.10 1.60 0.96 0.66 0.16 0.06 1.85 1981 0.84 0.55 0.21 0.10 1.68 0.95 0.67 0.16 0.06 1.86 1982 0.88 0.54 0.20 0.09 1.71 0.94 0.70 0.17 0.07 1.88 1983 0.87 0.52 0.19 0.08 1.65 0.89 0.67 0.17 0.07 1.81 1984 0.79 0.54 0.18 0.07 1.58 0.86 0.65 0.17 0.07 1.74 1985 0.81 0.55 0.18 0.07 1.60 0.87 0.66 0.20 0.07 1.81 1986 0.76 0.55 0.17 0.06 1.54 0.91 0.68 0.22 0.09 1.89 1987 0.74 0.54 0.17 0.06 1.51 0.91 0.70 0.23 0.09 1.92 1988 0.71 0.54 0.17 0.07 1.49 -- -- -- -- -- 1989 0.70 0.52 0.17 0.07 1.45 -- -- -- -- -- 1990 0.73 0.52 0.18 0.07 1.50 -- -- -- -- -- 1991 0.74 0.50 0.17 0.07 1.47 -- -- -- -- -- 1992 0.76 0.48 0.17 0.06 1.47 -- -- -- -- -- 1993 0.79 0.51 0.16 0.06 1.53 -- -- -- -- -- • Marc Luy, Olga Pötzsch636 Notes: -- no estimates available; data basis of the estimates for Western Germany for the years 1959-1984 Birg et al. (1990), 1985 combination Birg et al. (1990)/Kreyenfeld (2002), 1986-1994 Kreyenfeld (2002), 1995 combination Kreyenfeld (2002)/perinatal survey, 1996-1998 perinatal survey, 1999-2001 offi cial statistics (marital births), 2002-2007 Krey- enfeld et al. (2010), 2008 combination Kreyenfeld et al. (2010)/offi cial statistics (all births); data basis of the estimates for Eastern Germany for the years 1955-1987 offi cial statistics of the GDR, 1996-1999 perinatal survey, 2000-2001 combination perinatal survey/Kreyenfeld et al. (2010), 2002-2007 Kreyenfeld et al. (2010), 2008 combination Kreyenfeld et al. (2010)/ offi cial statistics (all births); total TFR* calculated from TFR1*+TFR2*+TFR3*+TFR4+ (see section on data and methods). Western Germany Eastern Germany Year TFR1* TFR2* TFR3* TFR4+* TFR* TFR1* TFR2* TFR3* TFR4+* TFR* 1994 0.80 0.50 0.16 0.06 1.52 -- -- -- -- -- 1995 0.72 0.52 0.15 0.07 1.47 -- -- -- -- -- 1996 0.78 0.57 0.16 0.08 1.58 0.75 0.49 0.12 0.07 1.42 1997 0.75 0.60 0.21 0.10 1.64 0.72 0.55 0.15 0.06 1.48 1998 0.74 0.54 0.16 0.06 1.51 0.78 0.52 0.16 0.07 1.51 1999 0.75 0.56 0.16 0.06 1.53 0.83 0.49 0.14 0.06 1.52 2000 0.74 0.57 0.16 0.06 1.53 0.93 0.46 0.10 0.05 1.55 2001 0.75 0.58 0.17 0.06 1.55 0.93 0.45 0.10 0.05 1.53 2002 0.80 0.55 0.17 0.07 1.58 0.88 0.47 0.12 0.05 1.52 2003 0.82 0.55 0.17 0.07 1.61 0.90 0.48 0.11 0.05 1.55 2004 0.82 0.56 0.17 0.07 1.62 0.87 0.50 0.12 0.06 1.54 2005 0.78 0.55 0.17 0.07 1.57 0.78 0.48 0.14 0.07 1.45 2006 0.80 0.57 0.19 0.08 1.63 0.80 0.57 0.16 0.06 1.59 2007 0.85 0.59 0.20 0.08 1.71 0.89 0.63 0.16 0.07 1.75 2008 0.83 0.57 0.18 0.08 1.66 0.78 0.60 0.18 0.11 1.62 2009 -- -- -- -- -- -- -- -- -- -- Annex 2 (continuation) Published by / Herausgegeben von Prof. Dr. Norbert F. Schneider Layout and print: Federal Institute for Population Research, Wiesbaden (Germany) Managing Editor / Redaktion Frank Swiaczny Copy Editor / Schlussredaktion Dr. Evelyn Grünheid Scientifi c Advisory Board / Wissenschaftlicher Beirat Jürgen Dorbritz (Wiesbaden) Paul Gans (Mannheim) Johannes Huinink (Bremen) Marc Luy (Wien) Clara H. Mulder (Groningen) Notburga Ott (Bochum) Peter Preisendörfer (Mainz) Comparative Population Studies – Zeitschrift für Bevölkerungswissenschaft www.comparativepopulationstudies.de ISSN: 1869-8980 (Print) – 1869-8999 (Internet) Board of Reviewers / Gutachterbeirat Martin Abraham (Erlangen) Laura Bernardi (Lausanne) Hansjörg Bucher (Bonn) Claudia Diehl (Göttingen) Andreas Diekmann (Zürich) Gabriele Doblhammer-Reiter (Rostock) Henriette Engelhardt-Wölfl er (Bamberg) E.-Jürgen Flöthmann (Bielefeld) Alexia Fürnkranz-Prskawetz (Wien) Beat Fux (Zürich) Joshua Goldstein (Rostock) Karsten Hank (Mannheim) Sonja Haug (Regensburg) Franz-Josef Kemper (Berlin) Michaela Kreyenfeld (Rostock) Aart C. Liefbroer (Den Haag) Kurt Lüscher (Konstanz) Dimiter Philipov (Wien) Tomáš Sobotka (Wien) Heike Trappe (Rostock) © Federal Institute for Population Research 2011 – All rights reserved