生育进度效应调整指标研究的新进展

随着经济和社会的不断发展,生育推迟现象在全世界范围内日益普遍。由于生育推迟所产生的进度效应会对生育水平造成影响,因此,如何测度生育进度效应便成了人口学界研究的重要内容。自Bongaarts和Feeney的去进度效应总和生育率提出以来,各种新的改进方法与指标不断出现。本文对生育进度效应调整指标的新进展及具体指标进行梳理与比较。从时期角度出发,主要包括方差效应调整后的TFR、PATFR*、调整后的TFRSUV_N和ITFR四种指标;从队列角度出发,主要包括TFRp*、TFR†和ACF三种指标,这些指标有各自的优缺点。研究发现:首先,由于不同去进度效应改进指标的假设、适用条件、研究角度、改进方向都不同,很难有一套数据同时适用于多种去进度方法,因此,生育进度效应的诸多改进指标并没有哪个指标“更好”,只有“更合适”;其次,绝对的去进度效应只能停留在理论层面,而实际上却很难做到,种种去进度方法都只是一种“相对的去”,而不是“绝对的去”。过去我们所熟悉的进度效应是生育推迟,而目前世界范围内生育推迟速度开始逐渐放缓,未来我们甚至不能排除生育推迟在某个时期或某些区域会发生逆转,届时可能会出现与目前影响方向相反的进度效应,这可能是下一步关于生育进度效应研究应该注意的新方向。     

A demographic explanation for the recent rise in European fertility

Between 1998 and 2008 European countries experienced the first continent-wide increase in the period total fertility rate (TFR) since the 1960s. After discussing period and cohort influences on fertility trends, we examine the role of tempo distortions of period fertility and different methods for removing them. We highlight the usefulness of a new indicator: the tempo- and parity-adjusted total fertility rate (TFRp*). This variant of the adjusted total fertility rate proposed by Bongaarts and Feeney also controls for the parity composition of the female population and provides more stable values than the indicators proposed in the past. Finally, we estimate levels and trends in tempo and parity distribution distortions in selected countries in Europe. Our analysis of period and cohort fertility indicators in the Czech Republic, Netherlands, Spain, and Sweden shows that the new adjusted measure gives a remarkable fit with the completed fertility of women in prime childbearing years in a given period, which suggests that it provides an accurate adjustment for tempo and parity composition distortions. Using an expanded dataset for ten countries, we demonstrate that adjusted fertility as measured by TFRp* remained nearly stable since the late 1990s. This finding implies that the recent upturns in the period TFR in Europe are largely explained by a decline in the pace of fertility postponement. Other tempo-adjusted fertility indicators have not indicated such a large role for the diminishing tempo effect in these TFR upturns. As countries proceed through their postponement transitions, tempo effects will decline further and eventually disappear, thus putting continued upward pressure on period fertility. However, such an upward trend may be obscured for a few years by the effects of economic recession.     

Birth delays skew developing world's fertility figures

This article explains that birth delays skew developing world's fertility figures. When successive groups of women who have delayed childbearing start having children, the rapid fertility decline stalls. Such change in the timing of childbearing skews the total fertility rate (TFR). Analysis of the tempo component of TFR trends in Taiwan suggests that tempo effects reduced its TFR by about 10% in the late 1970s and early 1990s and by about 19% in the late 1980s. In Colombia, on the basis of increasing mean maternal age at childbirth between the 1970s and the late 1980s, tempo distortions of the TFR during the most of the 1980s seem likely. Moreover, many developing countries are now experiencing rapid fertility declines that are in part attributable to tempo changes. These changes have accelerated past fertility transitions, but they also make these countries vulnerable to future stalls in fertility when the delays in childbearing end. Since fertility reductions caused by tempo effects lead to real declines in birth rates and hence in population growth, countries that wish to reduce birth rates can take actions that encourage women to delay marriage and the onset of childbearing.     

Timing effects and the interpretation of period fertility

Low fertility levels and later childbearing in many developed countries have reinvigorated the debate between period and cohort perspectives on fertility and on the meaningfulness of the period total fertility rate (TFR). Here, fertility-timing effects are defined as level changes in period fertility that do not reflect level changes in the completed fertility of cohorts. That definition leads to the average cohort fertility (ACF) as a measure of period fertility adjusted for timing effects. In an influential paper, Bongaarts and Feeney (1998) presented an alternative approach and a different measure, TFR*, to adjust for timing effects. Here, the two measures are compared. In the context of model populations, the ACF performs well, reflecting an average of the fertility of the active cohorts. The Bongaarts-Feeney TFR*, however, is frequently unreliable and can be erratic when there are cycles in period timing. When applied to twentieth-century U.S. experience, the TFR* behaves like a period measure and yields adjustments that are often wide of the mark. The ACF shows the stability associated with cohort measures and quantifies the substantial impact that timing effects had during the "birth dearth" of the 1970s. The period TFR reached a low of 1.74 in 1976, but the ACF never went below 2.06 during the 1970s.     

Variance effects in the bongaarts-feeney formula

Bongaarts and Feeney have recently proposed an adjusted total fertility rate to disentangle tempo effects from changes in the quantum of fertility. We propose an extension to the Bongaarts and Feeney formula that includes variance effects: that is, changes in the variance of the fertility schedule over time. If these variance effects are ignored, the mean age at birth and the adjusted total fertility rate are biased. We provide approximations for these biases, and we extend the TFR adjustment to fertility schedules with changing variance. We apply our method to the Swedish baby boom and bust, and show that variance effects are important for evaluating the relative contributions of tempo and quantum effects to the fertility change from 1985 to 1995.     

The TFR and birth control]

Total fertility rate if (TFR) is a simple an straight forward measure of women's fertility. However, it is difficult to use the TFR as a target measure in FP programs. If TFR level is set as a target for a particular year, how can women's fertility be regulated to achieve this target? The following analysis suggests a simple model to control the proportion of birth parity. First, the TFR is decomposed into a parity- specific TFR. The parity-specific TFR can be worked out using coefficients of the regression models calculated from data of previous fertility surveys. Once the TFR is given, the parity-specific total fertility can be calculated using a model with coefficients from empirical data. Then the number of births of each parity may be calculated from the parity-specific TFR using the female age structure in a particular year, the survival probability, and the standard fertility model for each parity. When the number of surviving children of each women at child-bearing age is known, the desired proportion of births of each parity can be calculated using the standard birth probability during a years. From these models, it would be possible to calculate how many women can have their first child/year, and how many can have the second. Thus, family planning organizations would be in a position to formulate a birth quota on the basis of the above information.     

A comment on total fertility]

Total fertility rate (TFR) cannot be interpreted as the average number of children a couple will have, as the TFR is influenced by a number of factors. The most important factor is the fertility rate of each individual age group. A decline in these rates brings about a decline in the TFR, but other elements also play a part. Another important factor is the age at which women are getting married. The natural childbearing years run for 35 years, from age 15 through 49, but if women are not permitted to marry before age 23, this period will be reduced to 27 years, which would in turn lower the TFR. The number of children each couple is permitted to bear also has an influence on the TFR; the lower the number of children permitted, the lower the TFR. Another factor which affects the TFR is the number of women who, by law, cannot bear any more children. On a long-term basis, it does not appear that the TFR will drop to 1 by the end of this century; it will fall somewhere between 1 and 2. If it is maintained below 1.5-1.6 after 1985, and continues to gradually decline, China's population will be approximately 12 billion at the end of the 20th/Century, and the aging of the population will not become a serious problem.     

Is Stepfamily Status Associated With Cohabiting and Married Women’s Fertility Behaviors?

Children from prior relationships potentially complicate fertility decision-making in new cohabitations and marriages. On the one hand, the “value of children” perspective suggests that unions with and without stepchildren have similar—and deliberate—reasons for shared childbearing. On the other hand, multipartnered fertility (MPF) research suggests that childbearing across partnerships is often unintended. Using the 2006–2010 National Survey of Family Growth and event-history models, I examine the role of stepfamily status on cohabiting and married women’s fertility and birth intendedness, with attention to union type and stepfamily configuration. Adjusting for covariates, women in stepfamily unions are more likely to have a first shared birth in a union than women in unions in which neither partner has children from past relationships, but stepfamily births are less likely to be intended than unintended. Further, this association varies by union type: married women have similar birth risks across stepfamily status, but births are less likely to be intended in marital stepfamilies. For cohabitors, women in a stepfamily are more likely to have a birth than women in nonstepfamily unions, with no differences in intendedness. Configuration (whose children and how many) also matters; for instance, women with one child from a past relationship are more likely to have a birth and to have an intended than unintended birth than women with other stepfamily configurations. It appears that children from either partner’s prior relationships influences subsequent fertility decision-making, undermining the utility of the “value of children” perspective for explaining childbearing behaviors in complex families.     

The End of the Fertility Transition in the Developed World

By the late 1990s the average period total fertility rate in the developed world had declined to 1.6, a level substantially lower than projected in the 1970s and 1980s. This article examines recent trends and patterns in fertility in the developed world with particular emphasis on the effects and implications of changes in the timing of childbearing. The main objective is to demonstrate that while fertility in these countries is indeed low, women's childbearing levels are not as low as period measures such as the total fertility rate suggest. To obtain a full understanding of the various dimensions of fertility change. several indicators are examined, including period and cohort fertility by birth order and childbearing preferences. An analysis of these indicators demonstrates that period fertility measures in many developed countries are temporarily depressed by a rise in the mean age at childbearing. The distortion of the TFR is as great as 0.4 births per woman in Italy and Spain. These effects have been present in many developed countries since the 1970s and could continue for years into the future. But tempo effects are temporary, and once the postponement of childbearing ends—as it eventually must—the corresponding fertility‐depressing effect stops, thus putting upward pressure on period fertility. Countries with very low fertility and substantial tempo effects may well experience rises in fertility in the near future if the timing of childbearing stabilizes. Even if this happens, however, it seems unlikely that fertility will rebound to the replacement level.     

The fertility impact of changes in the timing of childbearing in the developing world

This study examines the role of tempo effects in the fertility declines of less developed countries. These effects temporarily inflate the total fertility of a population during periods when the age at childbearing declines and deflate it when childbearing is postponed. An analysis of data from the World Fertility Surveys and the Demographic and Health Surveys demonstrates that fertility trends observed in many less developed countries are likely to be distorted by changes in the timing of childbearing. In most countries women are delaying childbearing, which implies that observed fertility is lower than it would have been without tempo changes. This pattern is most clearly documented in Taiwan, where accurate birth statistics from a vital registration system make it possible to estimate the tempo components of fertility annually from 1978 to 1993. The small but unexpected rise in the total fertility of Colombia in the early 1990s is attributed to a decline in the negative tempo distortion that prevailed in the 1980s. Similar interruptions of ongoing fertility declines may occur in the future in other countries when existing negative tempo effects are removed.     

Sweden faces zero population growth

In this discussion of Sweden as it approaches zero population growth, focus is on the following: population growth in perspective, fertility trends (childbearing concentrated and cohort versus period fertility), marital status (non-marital cohabitation, out-of-wedlock births, and divorce), women's changing status (increasing education and increasing employment), constraints and supports for women's dual role (family allowances and housing), birth control (contraceptive methods and practice and abortion), mortality trends, changing age structure and the elderly (average population age and proportion of elderly and cost of elderly support), international migration (from emigration to immigration and demographic impact of immigration), immigration policy, recent population debate (immigration issues and facing zero population growth). Since 1900 the primary features of Sweden's demographic history are a continuing decline in the birth rate to very low levels -- relieved by some upward movement in the 1940s and 1960s -- and a marked shift in the migration balance from emigration to immigration. It is almost entirely because of immigration that Sweden's population growth rate has not yet turned negative. If Swedish women were to continue to bear children at the rate that all women in the reproductive ages actually did in 1978, each women would end up with an average well below the level necessary to exactly replace each adult in the population leaving migration out, an annual total fertility rate of 2.1 children per woman would have to be sustained for births and deaths to be in balance under the low mortality conditions prevaling in Sweden.     

Low Fertility Trap:Theories,Facts and Implications

The low Fertility Trap Hypothesis proposes that there are three self-reinforcing mechanism--demographic,sociological and economic,working towards a downward spiral in future fertility.Once TFR drops below 1.5,it will be difficult to recover.The fertility recovery emerging in many countries across the world has changed the lowfertility trap theory and also the justification of the theory itself.So low-fertility trap is more likely a pattern summarized from a short-time phenomenon than a generalized social law.As with China,the current fertility level is above 1.5 births per woman,and China is not in the "Low-fertility trap".Moreover,most recent surveys suggests that current fertility intention in China is above 1.8 births per woman and more than60 percent of people would have a second child if there is an adjustment of fertility policy.In addition,birth postponement is still playing an important role in reducing TFR in China.Thus,with the high fertility intention,adjustment of family planning policy and decreasing tempo effect,TFR in China will experience upturn but not further decline in the near future.It is lack of evidence to conclude that China has already been or is going to be trapped in low fertility.     

How Far Has Fertility in China Really Declined?

According to births in the last year as reported in China's 2000 census, the total fertility rate (TFR) in the year 2000 in China was 1.22 children per woman. This estimate is widely considered to be too low, primarily because some women who had out‐of‐quota births according to China's one‐child family policy did not report those births to the census enumerator. Analysis of fertility trends derived by applying the own‐children method of fertility estimation to China's 1990 and 2000 censuses indicates that the true level of the TFR in 2000 was probably between 1.5 and 1.6 children per woman. A decomposition analysis of change in the TFR between 1990 and 2000, based on our best estimate of 1.59 for the TFR in 2000, indicates that about two‐fifths of the decline in the conventional TFR between 1990 and 2000 is accounted for by later marriage and less marriage, and three‐fifths by declining fertility within marriage. The analysis also applies the birth history reconstruction method of fertility estimation to the two censuses, yielding an alternative set of fertility estimates that are compared with the set derived by the own‐children method. The analysis also includes estimates of trends in fertility by urban/rural residence, education, ethnicity, and migration status. Over time, fertility has declined sharply within all categories of these characteristics, indicating that the one‐child policy has had large across‐the‐board effects.     

浅析中国1991～2000年生育模式变化对生育水平的影响

分析生育模式的变化对生育水平的影响 ,通过计算 1 991～ 2 0 0 0年中国去进度效应总和生育率TFR’ ,清楚地看出 ,提高初婚年龄和拉大一孩至二孩生育间隔所造成的生育模式的变化导致中国 1 0年间TFR偏低。去进度效应总和生育率TFR’较之TFR更加接近中国妇女的实际终身生育水平     

A sensitivity analysis of the bongaarts-feeney method for adjusting bias in observed period total fertility rates

Our sensitivity analysis shows that the adjusted TFR'(t) using the formula of Bongaarts and Feeney (1998), which assumes an invariant shape for the fertility schedule, usually does not differ significantly from an adjusted TFR"(t) that allows the shape of the fertility schedule to change at a constant annual rate. Because annual changes in the shape of the fertility schedules often are approximately constant except in abnormal conditions, the Bongaarts-Feeney (B-F) method is generally robust for producing reasonable estimates of the adjusted TFR'(t). The adjusted TFR'(t) neither represents any real cohort experiences from the past nor forecasts any future trend. It merely provides an improved reading of the period fertility measure, which reduces the tempo distortion.     

New insights into the fertility patterns of recent Polish migrants in the United Kingdom

There have been important changes in the United Kingdom’s fertility and immigration in the past decade, with a large share contributed by migrants from Poland. A detailed understanding of Polish migrant fertility is lacking, however, because the relevant data are not routinely collected. This paper provides new insights into the fertility patterns of Polish migrants in the UK, and compares these patterns with those of other large immigrant groups, the UK-born population and in Poland. We use the UK Labour Force Survey with the Own Children Method, illustrating the potential of survey data for estimating immigrant fertility in settings where other data are unavailable. We first compare the fertility patterns of recent Polish migrants with those of other key recent immigrant groups and the UK-born population; estimating Age-Specific Fertility Rates (ASFRs), and Total Fertility Rates (TFRs), by country of birth for the 2004–2012 period; the proportions in each immigrant group that arrive without children; and of those childless at arrival the proportions of women who go on to have births within a short period after arrival. Next, we compare the ASFRs and TFR for Polish migrant women with those observed in Poland. Our results show that the fertility of Polish migrants is among the lowest for all population subgroups in the UK, and that Polish migrants are less likely to have children soon after arrival than other immigrant groups. The findings are consistent with migration not being so closely linked to family formation for Polish migrants as it is for immigrants in the comparison groups. We also find that the fertility patterns of Polish migrants are different from those observed in Poland with a later childbearing profile and a slightly higher TFR.     

Baby boomlet for older mothers?

In recent years, a number of celebrities have begun childbearing after age 35. The phenomena of older first-time mothers has received a great deal of attention in the popular press. Are these celebrities indicative of a national trend? Does the increase in fertility portend a reversal of the declines in fertility which have been occurring since the baby boom? The present paper uses central and cumulative birth rates for cohorts of American white women born between 1882 and 1953 to investigate childbearing between ages 35 and 50. While there has been a noticeable upsurge in first birth rates for cohorts in their mid to late 30s in recent years, overall central birth rates for women in their 30s are among the lowest on record, with cumulative birth rates at record low levels. A major reason for this is that these women are having relatively few third and higher order births. These cohorts will need to have a relatively high proportion of births in their older years of childbearing in order to reach replacement level. However, attaining replacement level is unlikely because such a high proportion of women have remained childless at ages 35–40 and a relatively low proportion are having three or more children.     

Immigration to the UK from High‐Fertility Countries: Intergenerational Adaptation and Fertility Convergence

The fertility of immigrants' children increasingly shapes the ethnic diversity of the population in Western Europe. However, few data are available on the fertility patterns of immigrants and their offspring. This article provides new fertility estimates of immigrants and immigrants' children by ethnic group in the United Kingdom that may provide better‐informed fertility assumptions for future population projection models. The impact of migration‐specific tempo effects on the period TFR of immigrants is analyzed. Among the results, intergenerational fertility transitions strongly contribute both to fertility convergence between ethnic groups and to fertility “assimilation” or “intergenerational adaptation” to the UK mainstream childbearing behavior. Ethnic fertility convergence, particularly marked for populations originating from high‐fertility countries, reflects in part decreasing fertility in sending countries and in part intergenerational adaptation to the UK mainstream. Higher educational enrollment of the daughters of immigrants may partly explain their relatively lower fertility.     

China's Below‐Replacement Fertility: Recent Trends and Future Prospects

Between 1970 and 1990, China experiencoed a rapid and sharp fertility decline—from total fertility rates of approximately six births to two. The degree to which Chinese fertility has continued to fall after 1990 is controversial. We use survey data from the 1997 National Population and Reproductive Health Survey and from the 2001 Reproductive Health and Family Planning Survey to document recent trends in Chinese fertility. Our estimates provide further evidence that China's fertility is well below‐replacement level at the turn of the twenty‐first century—with TFR levels of approximately 1.5 children per woman. Trends in parity‐specific cohort fertility by age also suggest below replacement completed fertility for cohorts still in the childbearing years. In the article's second section, we identify key components of low period fertility in order to frame our discussion of two questions: 1) in what ways is Chinese low fertility different from/similar to that in other low‐fertility countries? And 2) what are the likely future trends in Chinese fertility?     

On Postponement and Birth Intervals

Much of the literature on fertility transition presumes that birth control is practiced either to limit family size or to space births. This article argues that women also use birth control to postpone pregnancy. Postponement is not synonymous with spacing. It arises when women delay their next birth for indefinite periods for reasons unrelated to the age of their youngest child, but without deciding not to have any more children. Postponement has a distinctive impact on the shape of birth‐interval distributions that differs from the impacts of family size limitation, birth spacing, or a mixture of the two behaviors. Some populations, such as that in South Africa, have developed fertility regimes characterized by birth intervals far longer than can be accounted for by birth spacing. Postponement of further childbearing that eventually becomes permanent may be an important driver of the transition to lower fertility in sub‐Saharan Africa.