Birth month,school graduation,and the timing of births and marriages

We investigated the timing of fertility and marriage in Sweden using exogenous variation in the age at school graduation that results from differences in birth month. Our analysis found that the difference of 11 months in the age at leaving school between women who were born in two consecutive months, December and January, implies a delay in the age at first birth of 4.9 months. This effect of delayed graduation also persists for the timing of second births and first marriages, but it does not affect completed fertility or the overall probability of marriage before age 45. These results suggest the existence of a relatively rigid sequencing of demographic events in early adulthood, and the age at graduation from school emerges as an important factor in determining the timing--but not the quantum--of familyformation. In addition, these effects point to a potentially important influence of social age, defined by an individual's school cohort, instead of biological age. The relevance of social age is likely due to social interactions and peer-group influences exerted by individuals who are in the same school cohort but are not necessarily of the same age.     

Sex preference versus number preference: the case of Korea

The author argues that the effect of sex preference must be disentangled from the effect of number preference in Korea. This study tests--with hazard models--the effect of the number of previous children on the next birth according to the sex composition of previous children. Data were obtained from the 1974 Korean Fertility Survey. This paper also analyzes the timing of childbearing in recent periods in order to determine whether replacement-level fertility is temporary or permanent. The ideal number of children declined from 3.9 children in 1965 to 2.1 in 1991. The age-specific fertility rates for ages 20-24 years declined rapidly during the late 1980s. The fertility rates among women aged 25-29 years and 30-34 years increased during 1985-90. The proportion of fertility among women aged 20-29 years increased from 67.9% in 1975 to 86.6% in 1984. Women born in the late baby boom period of the late 1950s to mid-1960s reached prime reproductive age during the late 1980s and 1990s, but the crude birth rate remained about the same during 1985-92. A higher percentage of women (22.4%) born during 1955-59 remained single in 1990. During 1960-90, the percentage of women aged 20-24 years who were married declined. These trends indicate later age at childbearing and an explanation for the temporary nature of below-replacement fertility in the late 1980s. Korean women did not want to have more than 2 children, and the interval between first and second births increased since 1985. Among pregnancies of parity 2 conceived since 1985, over 90% of women with at least one son ended subsequent pregnancies by abortion compared to only 59% without sons. Hazard models of 1974 data reveal that son preference had an important effect on fertility. Fertility was higher among women with only daughters. Findings suggest that the value of sons must be measured at the societal and not at the individual level.     

Reporting of fertility events by men and women in rural Gambia

We conducted a survey of male and female fertility in rural villages in The Gambia and compared men and women's reports of recent pregnancy events in the aggregate and of children ever born for matched couples. Despite widespread polygyny and sex differences in fertility, men's and women's reports were similar. Small sex differences in reports of recent stillbirths and neonatal deaths were found. For matched couples, husbands reported 0.23 more children ever born than their wives on average, but discordant reporting had little effect on recent marital fertility rates. Modeling of discordant reports indicates that fertility reports are more likely to be underestimated by both men and women for their earliest marriages. Reliable fertility data can be collected from men in this population.     

Nonmarital childbearing: Influences of education,marriage, and fertility

We examined the determinants of nonmarital fertility, focusing on the effects of other life-course events: education, marriage, marital dissolution, and marital fertility. Since these determinants are potentially endogenous, we modeled the processes that generate them jointly with nonmarital fertility and accounted for the sequencing of events and the unobserved correlations across processes. The results showed that the risk of nonmarital conception increases immediately after leaving school and that the educational effects are less pronounced for black women than for other women. The risk is lower for previously married women than for never-married women, even controlling for age, but this reduction is significant only for black women. The more children a woman already has, the lower her risk of nonmarital childbearing, particularly if the earlier children were born during a previous marriage. Ignoring endogeneity issues seriously biases the estimates of several substantively important effects.     

Cohort estimates of nonmarital fertility for U.S. Women

Historical trends in U.S. nonmarital fertility have been compiled almost exclusively from vital statistics on births. This paper complements this historical record by providing cohort estimates of nonmarital fertility for cohorts of U.S. women spanning approximately 50 years of cohort experience. Life table estimates using retrospective marital and fertility histories in the June 1980, 1985, 1990, and 1995 Current Population Surveys reveal nonnegligible levels of nonmarital fertility historically. For women born between 1925 and 1929, nearly 1 in 10 had at least one nonmarital birth by age 30. For women born between 1965 and 1969, more than 1 of 4 had one or more nonmarital births by age 30, with roughly 1 of5 white, 3 of 5 black, and 1 in 3 Hispanic women having at least one nonmarital birth by age 30. Life table estimates reveal a twofold increase between ages 20 and 30 in the percentage of women with at least one child outside of formal marriage for all cohorts of white and Hispanic women, and an increase of roughly two-thirds for all cohorts of black women. I also document qualitative differences in nonmarital fertility by race/ethnicity, with the percentage of nonmarital births following a divorce or marital separation for white women approximately twice that for black or Hispanic women. Finally, I introduce a new measure, the cohort nonmarital fertility ratio (CNMFR), which provides a cohort complement to the standard period nonmarital fertility ratio. Conservative estimates reveal a roughly threefold increase in the CNMFR for women born from 1925-1929 to 1950-1954 for both whites and blacks, despite substantially higher levels of nonmarital fertility among black women. Overall, these findings reveal surprisingly high levels of nonmarital fertility for women born since the 1920s and confirm that nonmarital fertility has become an increasingly substantial component of overall U.S. fertility.     

关于中国1990年代低生育水平的再讨论

本文根据全国第五次人口普查样本计算了 1 990年代各年份的分性别平均初婚年龄 ,这一结果再次表明这一时期中初婚年龄有显著提高。本文还根据以往历次调查的各年份年龄别生育率按队列计算了累计生育率 ,结果发现 2 0 0 0年时各队列的累计生育率水平高于五普数据中各队列的平均活产子女数。本文还就队列累计生育率计算结果详细分析了 1 990年代终身生育水平的趋势。这些分析从一个新的角度说明 ,1 990年代各队列的终身生育水平也在发生显著的下降 ,正在接近现行生育政策所要求的水平     

Birth variations in populations which practise family planning

In the first section it is demonstrated that permanent periodicities may appear in populations, in which fertility occurs at two or more ages, separated by ages, in which there is no fertility at all. It is also shown that where periodicity does disappear, this may take much longer than is usually assumed, before the stable age distribution is attained.

The last section of the paper is based on Swedish data relating to female fertility for single-year cohorts and for periods. It is demonstrated that fertility behaviour of cohorts from different decades has varied considerably, not least as regards birth timing. This explains why the period fertility rate has varied in such an irregular fashion, whereas the rate for cohorts has moved much more regularly; after the original decline to an all-time low for the cohorts born around 1905, there has been a slow, and on the whole, regular increase. This increase is largely explained by a rise in nuptiality. If the total fertility rate required for reproduction is computed, it is seen that no cohorts born after about 1885 have reproduced themselves, and that for the cohorts born between 1895 and 1920 the gap was considerable.     

Birth variations in populations which practise family planning

Abstract In the first section it is demonstrated that permanent periodicities may appear in populations, in which fertility occurs at two or more ages, separated by ages, in which there is no fertility at all. It is also shown that where periodicity does disappear, this may take much longer than is usually assumed, before the stable age distribution is attained. The last section of the paper is based on Swedish data relating to female fertility for single-year cohorts and for periods. It is demonstrated that fertility behaviour of cohorts from different decades has varied considerably, not least as regards birth timing. This explains why the period fertility rate has varied in such an irregular fashion, whereas the rate for cohorts has moved much more regularly; after the original decline to an all-time low for the cohorts born around 1905, there has been a slow, and on the whole, regular increase. This increase is largely explained by a rise in nuptiality. If the total fertility rate required for reproduction is computed, it is seen that no cohorts born after about 1885 have reproduced themselves, and that for the cohorts born between 1895 and 1920 the gap was considerable.     

Fertility of Australian birth cohorts: Components and differentials

The paper examines the change in the level and pattern of fertility that took place in the post-1971 period, and the downward completed fertility of successive generations of Australian women born since 1933–37. The change in cohort fertility is assessed in terms of the cohort parity progression ratios, and the four components of cohort total fertility: the proportion of women who proceeded to have a birth, mean age at first birth, mean age at last birth, and average interbirth interval for women who had at least two births. The other aspects discussed are the cohort fertility differentials and the implications of the current trends for future fertility in Australia.     

Age,biological factors,and socioeconomic determinants of fertility: A new measure of cumulative fertility for use in the empirical analysis of family size

To influence the number of children ever born to a woman, socioeconomic variables must operate through behavioral and biological mechanisms such as the age at marriage, the level of fertility in the absence of deliberate fertility control, and the level of control exerted to reduce fertility within marriage. In this paper, we propose a new measure of cumulative fertility which is standardized for the age-fecundity relationship and for exposure to the risk of conception associated with duration of marriage. A simple model of fertility behavior which incorporates some of the mechanisms through which socioeconomic factors may affect fertility is developed and applied to data from the United States to demonstrate the properties of alternative measures of family size. The results indicate that use of the new measure allows more precise estimates of socioeconomic fertility relationships than would be obtained with children ever born or by sample stratification.     

Childhood nutrition and later fertility: Pathways through education and pre-pregnant nutritional status

Better childhood nutrition is associated with earlier physical maturation during adolescence and increased schooling attainment. However, as earlier onset of puberty and increased schooling can have opposing effects on fertility, the net effect of improvements in childhood nutrition on a woman’s fertility are uncertain. Using path analysis, we estimate the strength of the pathways between childhood growth and subsequent fertility outcomes in Guatemalan women studied prospectively since birth. Height for age z score at 24 months was positively related to body mass index (BMI kg/m²) and height (cm) in adolescence and to schooling attainment. BMI was negatively associated (−0.23 ± 0.09 years per kg/m²; p < . 05) and schooling was positively associated (0.38 ± 0.06 years per grade; p < .001) with age at first birth. Total associations with the number of children born were positive from BMI (0.07 ± 0.02 per kg/m²; p < .05) and negative from schooling (−0.18 ± 0.02 per grade; p < .01). Height was not related to age at first birth or the number of children born. Taken together, childhood nutrition, as reflected by height at 2 years, was positively associated with delayed age at first birth and fewer children born. If schooling is available for girls, increased growth during childhood will most likely result in a net decrease infertility.     

Fertility trends in rural Hebei Province,People's Republic of China

Background: The People's Republic of China (PRC) has conducted several different population policies since its establishment. Although fertility has declined dramatically in the past three decades, the degree to which this was the result of the different population policies is still under debate. Purpose: We attempt to evaluate the effect of the different formal population policies conducted in the PRC by looking at the fertility behavior of rural women. Unlike urban women, rural women experienced less social control (in the absence of a work unit) and received fewer benefits from adhering to the one-child policy. Data: The data analyzed were collected from a stratified sample of households from 288 villages in 9 counties of Hebei Province, PRC, between 1996 and 1999. The number of children ever born was reported by 4,168 ever-married women aged 25 and over who had had at least one birth. Findings: Our analysis indicates that the formal population policies of the PRC had little effect on the number of children ever born to rural women in Hebei. These retrospective data, by cohort, indicate consistently declining fertility since the revolution (1949). Limited child bearing was associated with age and the level of education. Controlling for the effect of age and education, women born after 1960, at whom the one-child policy was directed, actually had more children than older women. Conclusions: The Chinese fertility decline, at least as reflected in the experience of rural women in Hebei Province, derived mainly from secular changes in women's access to education and other social resources rather than from the direct effects of population policies.     

Marital dissolution,remarriage, and childbearing

Earlier models of fertility hypothesize that marital dissolution and remarriage influence subsequent childbearing. This issue is examined by comparing the fertility of those in disrupted marriages with that of those in stable marriages. The results indicate that, by transferring women into a nonmarried status, marital dissolution decreases childbearing. The data also suggest that discord reduces fertility even before separation occurs—separated women had reduced fertility during the two years just before separation. It was found that marital dissolution without remarriage operates to truncate childbearing, thus decreasing family size. Dissolution followed by remarriage, however, lengthens the childbearing span of whites and has no influence on average family size; remarrying white women are able to make up for the childbearing lost between marriages. For nonwhites, we found that dissolution and remarriage increase the average time to childbirth, but, even more importantly, these events greatly decrease the number of children born.     

广东“80后”生育意愿及其影响因素研究

改革开放后出生的一代人的生育意愿和意愿生育数量将表现出与父辈们不同的特征。本文采用广东省人口和计划生育委员会支持的调研数据,并通过实证研究发现：个人受教育程度、家庭收入、户籍状况、家庭结构及财产状况等因素共同影响着初育年龄意愿、理想生育数和生育性别意愿。总体来看,教育程度与经济因素是影响“80后”生育意愿的主要因素。同时,家庭养老压力也在一定程度上影响到他们的生育意愿。     

Is Fertility Behavior in Our Genes? Findings from a Danish Twin Study

This article investigates the fertility of Danish twins born during the periods 1870–1910 and 1953–64 in order to pursue two central questions for understanding human reproduction: Do genetic dispositions influence fertility and fertility-related behavior? Does the relevance of the “nature versus nurture” debate shift over time or with demographic regimes? The authors find that genetic influences on fertility exist, but that their relative magnitude and pattern are contingent on gender and on the socioeconomic environment experienced by cohorts. Among females born in 1880–90 and after 1955, about 30–50 percent of the variance in fertility is due to genetic influences; these influences are substantially smaller for earlier and for interim birth cohorts. Male fertility is generally subject to smaller genetic and larger shared-environment effects than female fertility. Because genetic effects are most prevalent in situations with deliberately controlled fertility and relatively egalitarian socioeconomic opportunities, the authors propose that the genetic dispositions affect primarily fertility behavior and motivations for having children. Analyses of fertility motivations, measured by age of first attempt to have a child, support this interpretation.     

中国人口生育变化及影响因素——基于第六次人口普查的分析

本文在"六普"汇总数据的基础上,定量分析中国人口的生育水平、生育模式的变化和生育变化的影响因素。研究发现,在生育水平持续下降的情况下,结构性因素逐渐成为左右未来中国生育水平走向的决定性因素;生育模式正在向初婚初育间隔扩大,生育孩次向低孩次集中的方向发展;尽管年龄别已婚生育率的变化使得中国一般生育率上升9.613%,在导致生育水平下降的各因素中,育龄妇女年龄结构、婚姻状态等人口因素的影响显得越来越重要。研究结果对于正确理解我国的人口形势,科学地规划和调整人口政策具有十分重要的意义。     

Birth and death in cities in the developing world

City dwellers in Sub-Saharan Africa have increased roughly 600% in the last 35 years. Throughout the developing world, cities have expanded at a rate that has far outpaced rural population growth. Extensive data document lower fertility and mortality rates in cities than in rural regions. But slums, shantytowns, and squatters' settlements proliferate in many large cities. Martin Brockerhoff studies the reproductive and health consequences of urban growth, with an emphasis on maternal and child health. Brockerhoff reports that child mortality rates in large cities are highest among children born to mothers who recently migrated from rural areas or who live in low-quality housing. Children born in large cities have about a 30% higher risk of dying before they reach the age of 5 than those born in smaller cities. Despite this, children born to migrant mothers who have lived in a city for about a year have much better survival chances than children born in rural areas to nonmigrant mothers and children born to migrant mothers before or shortly after migration. Migration in developing countries as a whole has saved millions of children's lives. The apparent benefits experienced in the 1980s may not occur in the future, as cities continue to grow and municipal governments confront an overwhelming need for housing, jobs, and services. Another benefit is that fertility rates in African cities fell by about 1 birth per woman as a result of female migration from villages to towns in the 1980s and early 1990s. There will be an increasing need for donors and governments to concentrate family planning, reproductive health, child survival, and social services in cities, particularly in Sub-Saharan Africa, because there child mortality decline has been unexpectedly slow, overall fertility decline is not yet apparent in most countries, and levels of migration to cities are anticipated to remain high.     

Fertility trends in Australia

Using published data from the Australian vital registration and census systems, several time series are compiled: crude birth rates from the 1860s; fertility rates from the 1880s; age-specific and parity-specific measures from the 191Os; cumulative fertility measures by birth year of parent beginning with the 1890s; and cumulative fertility measures for marriages by year contracted from the 1910s.The decline in fertility to the 1930s, the upswing to 1961, and declines thereafter revealed by annual fertility measures show far more variation than do measures of total generation fertility—2.7 children per woman born in 1893–95, 2.3 1906–10, 2.8 1921–25, and perhaps 3.0 for women born in the 1930s. Both annual and generation measures show a younger age at parenthood, a decrease in childlessness, and progressively fewer large families. In the light of present experience, it seems not unreasonable to project generation fertility of 2.5 children, implying a crude birth rate of about 20 per thousand for the next fifteen years or so.     

Presentation and establishment of a system of total progressive fertility rates and relevant models

Demographic studies necessarily rely on adequate and accurate statistical data. To take into consideration China's present situation of population control and planned birth practice, a system of total progressive fertility rate (TPFR) different from the parity progression ratio is established and its relevant model presented in order to make indicators used in analysing women's 1st marriage and fertility level reflect as closely as possible the actual situation. Here, TFR and TPFR, both used in analyzing fertility level, are compared so as to show that TPFR is a methodology more appropriate for use in the analysis of China's fertility. The model is based on the fact that women's vital events happen progressively from being born to completing childbearing. In composing the model, both women's age structure and parity structure are considered and the regularity of their changes with different years is defined. In China, the population development program has been brought into the overall social and economic development plan. Thus it is necessary to practice planned birth in order to make the population develop in a way which is in keeping with the social and economic development. Compared with other models or theories, it is more realistic to use the model discussed above in studies on China's population policy.     

Intergenerational Transmission of Age at First Birth in the United States: Evidence from Multiple Surveys

It is well established that the timing of childbearing is transmitted from parents to children in the United States. However, little is known about how the intergenerational link has changed over time and under structural and ideological transformations associated with fertility behaviors. This study first considers changes across two birth cohorts from the National Longitudinal Survey of Youth (NLSY) in the extent to which parents’ age at first birth is transmitted to their children. The first cohort includes individuals born during the late 1950s through the early 1960s (NLSY79), while the second includes individuals born in the early 1980s (NLSY97). Results from discrete-time event history analyses indicate that the intergenerational transmission of age at first birth significantly increased for both daughters and sons. These results were confirmed by analyses of data from three cycles of the National Survey of Family Growth spanning the same time period. Over this period, age at first childbirth became increasingly younger for children born to teenage mothers and increasingly older for those born to mothers who began parenthood after age 25. These patterns have important implications for the reproductive polarization hypothesis.