Age and marital status at first birth and the pace of subsequent fertility

Taking care to minimize the truncation bias inherent in cross-sectional data and controlling for other variables, this paper demonstrates the strong effects of both age and marital status at first birth on the pace of subsequent fertility. These effects are particularly strong in the interval immediately following the first birth but persist even into the fourth interval. Important differences are found with respect to the experience of rapid fertility, rather than in the mean lengths of intervals. These results add to the growing attention to the social dimensions of age as a variable in fertility processes.     

Peru's coming baby boomlet

There are grounds for reconsidering the United Nations' population projections for Peru. These projections assume that fertility will continue to decline after 1990 in a smooth and uninterrupted manner, but they ignore several factors related to recovery from the economic and political crises of the 1980s that could significantly alter the pace of decline. The alternative projections we present consider the possibility that Peru's fertility decline will temporarily slow. This alternative hypothesis is conservative in the sense that increases in birth rates are not anticipated, but substantial differences in population size and age structure materialize nonetheless. Moreover, these differences have important implications for future planning in terms of the number of children needing primary health care and education and the number of young adults seeking first-time employment.The authors are grateful to Maryann Belanger, Luis Rosero-Bixby, and Anne Marie Wills for helpful comments, to Wayne Appleton for computer support, and to Terence Kelly for graphics design.     

A cohort analysis of the timing of first birth and fertility in Ghana

This paper examines the nature of the inverse association between age at first birth and fertility across successive generations of Ghanaian women. Within the context of enhanced non-marital opportunities for contemporary women and declining fertility, we develop a rationale for and test the hypothesis that in a medium fertility environment as currently found in Ghana, the effect of age at first birth on fertility becomes more important than ever before. Five birth cohorts were identified (1938–1944; 1945–1949;1950–1954; 1955–1959; 1960–1964)from a merged file of the 1988, 1993 and 1998 Ghana Demographic and Health Surveys. The analyses were restricted to women over 35 years old at the time of the surveys, which allowed us to use current parity as a reasonable proxy for completed fertility. Preliminary results suggest that women who had first births early tend to have a higher number of births than those whose first births occur late, regardless of birth cohort. In multivariate analyses, the effect of age at first birth as a determinant of fertility was found to be more substantial among later cohorts. The implications of the findings are discussed.     

Multipartnered fertility among American men

Using the 2002 (Cycle 6) National Survey of Family Growth (NSFG), which was the first NSFG to interview men, we document the prevalence and correlates of sequential parenthood with different partners (multipartnered fertility) among a representative sample of American men. Nearly 8% of American men aged 15-44 report having had children with more than one partner, with sharp differences by age, race/ethnicity, and income-over one-third of poor black men aged 35-44 report having had children with two or more mothers, and 16% report children with three or more mothers. Fathers of two or more children by multiple partners appear to be more disadvantaged than fathers with two or more children by the same partner. Multipartnered fertility is strongly related to prior birth characteristics; men not in a coresidential union at the preceding birth are more likely to have their next birth with a new partner and controlling for prior-birth characteristics accounts for the elevated risk of Hispanics and blacks in baseline models. Results also suggest that multipartnered fertility is becoming more prevalent as younger cohorts transition to a new-partner birth more quickly and at a higher rate than older cohorts.     

Diverging fertility among U.S. women who delay childbearing past age 30

In this paper I examine the evolving association between educational attainment and the timing of births. In the late 1970s, women with four-year college degrees had lower first birth rates before age 30 than women with less education, but rates of first births were similar for the two groups after age 30. From the 1970s to the 1990s, first birth rates decreased before age 30 for all women, but increased after age 30 only for women with four-year college degrees. Parity 2 birth rates also increased for college graduates with a first birth after age 30. These results document widening educational differences in fertility timing between 1975 and 1995, which may reflect period changes at later ages in women's work and family lives.     

Individual and aggregate influences on the age at first birth

This study examines the role of both individual adolescent expectations of market and nonmarket income and aggregate influences on first birth timing for Blacks and Whites and for three birth cohorts of American women. Using two panels of the National Longitudinal surveys, results suggest that between-race differences in age at first birth result from differences in individual expectations about market and nonmarket income. Cohort differences in age at first birth result from relationship differences in both individual and aggregate influences, with aggregate influences differentially altering the role of individual expectations on first birth timing. These results suggest that employment policies that reduce poverty and increase wages would effectively delay childbearing. For Blacks, since early childbearing results from lower expectations about future economic success, similar fertility timing patterns between the races would result if Blacks had White employment and wage levels. Over time, these employment and wage policies will not only alter individual expectations about economic success but also will alter the impact of expectations on fertility timing.     

The construction of the fertility model of variable parity from family planning practice]

Understanding the changing patterns of age specific fertility under the planning system is essential for building a fertility model which reflects birth control policy implementation in China. In building a Parity Variable Fertility Model, 4 basic elements are to be considered: 1) psychosocial, and physiological variables, 2) patterns of the total fertility rate and age-specific fertility rate, 3) socioeconomic development, and 4) distribution of parity-specific fertility. THe natural fertility of women is 17, calculated from a 309-years childbearing period, with 17% of non-susceptible time. In China, about 86% of natural fertility is suppressed by various factors. In this model, the following variables are included: 1) The first marriage ratio, which is the proportion of women in each age group which enters into a first marriage. The range and spread of this ratio is closely associated with the first birth. 2) The first birth ratio, which is the proportion of a marriage cohort to have a first birth each year. 3) the birth interval, which determines the distribution of second births. 4) Regulation coefficient B, which represents birth control regulations which approximately determine the number of second-parity or higher order births. The difference between the fertility level generated from the Parity Variable Fertility Model and reality depends on the implementation of birth control program, the assumptions on regulation coefficients, and changes in social and cultural factors. The model is easy to use, especially for areas where the marriage and fertility records of women of child-bearing are well kept.     

What are the determinants of delayed childbearing and permanent childlessness in the United States?

This paper presents estimates of delayed childbearing and permanent childlessness in the United States and the determinants of those phenomena. The estimates are derived by fitting the Coale-McNeil marriage model to survey data on age at first birth and by letting the parameters of the model depend on covariates. Substantively, the results provide evidence that the low first birth fertility rates experienced in the 1970s were due to both delayed childbearing and to increasing levels of permanent childlessness. The results also indicate that (a) delayed childbearing is less prevalent among black women than among nonblack women; (b) education is an important determinant of delayed childbearing whose influence on this phenomenon seems to be increasing across cohorts; (c) education is positively associated with heterogeneity among women in their age at first birth; (d) the dispersion of age at first birth is increasing across cohorts; (e) race has an insignificant effect on childlessness; and (f) education is positively associated with childlessness, with the effect of education increasing and reaching strikingly high levels for the most recent cohorts.     

What’s happening to the age at first birth in the United States? A study of recent cohorts

This paper analyzes cross-cohort trends in the age pattern of women at first birth in the United States. The analysis involves fitting the Coale-McNeil marriage model to the age distribution of first birth frequencies for a number of recent white and nonwhite cohorts. Methodologically, the results (a) provide support for the application of the Coale-McNeil marriage model to first birth data, and (b) demonstrate the ability of the model to accurately project first birth fertility for cohorts which have yet to complete their childbearing years. Substantively the results indicate (a) that the proportion of women who will never have a first birth is increasing across cohorts and can be expected to be as high as .25 and .20 for recent white and nonwhite cohorts respectively; (b) that recent nonwhite cohorts have an appreciable number of first births at earlier ages than their white counterparts, as well as a lower mean age at first birth and increasingly less dispersion (across cohorts) in their age at first birth; and (c) that the mean age at first birth and the proportion of first births occurring between ages 25 and 34 is increasing across cohorts of white women but is stable across cohorts of nonwhite women.     

Father Absence and Accelerated Reproductive Development in Non-Hispanic White Women in the United States

Girls who experience father absence in childhood also experience accelerated reproductive development in comparison with peers with present fathers. One hypothesis advanced to explain this empirical pattern is genetic confounding, wherein gene-environment correlation (rGE) causes a spurious relationship between father absence and reproductive timing. We test this hypothesis by constructing polygenic scores for age at menarche and first birth using recently available genome-wide association study results and molecular genetic data on a sample of non-Hispanic white females from the National Longitudinal Study of Adolescent to Adult Health. We find that young women’s accelerated menarche polygenic scores are unrelated to their exposure to father absence. In contrast, polygenic scores for earlier age at first birth tend to be higher in young women raised in homes with absent fathers. Nevertheless, father absence and the polygenic scores independently and additively predict reproductive timing. We find no evidence in support of the rGE hypothesis for accelerated menarche and only limited evidence in support of the rGE hypothesis for earlier age at first birth.     

Findings and implications of a correlation analysis of the closed and the open birth intervals

A correlation analysis of data on four fertility variables viz. closed birth interval, open birth interval, age and parity, collected in a survey of about 2,000 married women in the reproductive ages in rural India, is carried out in order to study the interrelationships among these variables. Two hypotheses are formulated governing the relationship of the closed and open birth intervals with the fecundability distribution of fertile women, and Parity Progression Ratios which are largely influenced by the proportion of women becoming sterile after each parity. The data lend support to the hypothesis that while the closed intervals are influenced mainly by the distribution of fecundability of women of non-zero fecundability, the open birth intervals are influenced mainly by Parity Progression Ratios or the proportion of women becoming secondarily sterile after each parity. The analysis suggests that we can use the mean open intervals of women classified by parity as indices of fertility, and such an index is comparable to the index of average age of women of given parity. In areas where it is difficult to ascertain the correct age of women this might be of practical value.     

The Correspondence Between Fertility Intentions and Behavior in the United States

Using data from the 1979 National Longitudinal Survey of Youth, we describe the correspondence between intended family size and observed fertility for US men and women in the 1957–64 birth cohorts. Mean fertility intentions calculated from reports given in the mid‐20s modestly overstate completed fertility. But discrepancies between stated intent and actual fertility are common—the stated intent at age 24 (for both women and men) is more likely to miss than to match completed fertility. We focus on factors that predict which women and men will have fewer or more children than intended. Consistent with life‐course arguments, those unmarried, childless, or (for women) still in school at approximately age 24 were most likely to underachieve their intended parity (i.e., had fewer children than intended at age 24). We discuss how such discrepancies between intentions and behavior may cumulate to produce sizable cross‐group fertility differences.     

Trends in the determinants of early childbearing

This study uses data from the young women's and new youth cohort of the National Longitudinal Surveys of Youth Labor Market Experience to examine the extent to which socioeconomic background factors and race have changed in their ability to predict a first birth before age 19 between 1968 and 1980 for women aged nineteen to twenty-three. The authors find little support for their hypothesis that the increasing availability of contraception and abortion for young women from all social classes reduces the traditionally strong inverse association between social class and early childbearing. There is evidence that, even after controlling for changes in socioeconomic background factors, black young women are significantly more likely than their white counterparts to bear children before age 19 in 1980 and the relative gap between races in this regard did not alter perceptively during that period.Prepared for presentation at the Population Association of America meetings, April/May 1987. The authors wish to thank Ronald D'Amico and Susan H. Mott for their helpful comments. This report was partially prepared under a contract with the U.S. Department of Labor with funds provided through an interagency agreement with the National Institute of Child Health and Human Development. Interpretations or viewpoints in this document do not necessarily represent the official position or policy of the Department of Labor or the NICHD.     

Parental underinvestment: A link in the fertility-mortality continuum

Selective parental investment in siblings has been used to describe differential mortality rates. Using data from 986 Filipino women who had an average of 4.8 live births, a LISREL and six sets of regression models support the hypothesis that fertility is linked to underinvestment and that mortality, as a consequence, is linked to high birth order. The analysis also identifies intervening factors associated with this relationship. Age of mother at childbirth showed a strong influence on the relationship of birth order and infant and child mortality; correlations are stronger among older than youger mothers. However, even after the effect of age of mother at childbirth was partialled out, the effect of birth order on infant and child mortality remained significant and substantial. The conclusion is that parental underinvestment represents a link between fertility and mortality during infancy and early childhood that has not been described previously. Policy makers appear to have overlooked parental underinvestment in favor of more obvious economic and health mediators.     

Is the Association Between Education and Fertility Postponement Causal? The Role of Family Background Factors

A large body of literature has demonstrated a positive relationship between education and age at first birth. However, this relationship may be partly spurious because of family background factors that cannot be controlled for in most research designs. We investigate the extent to which education is causally related to later age at first birth in a large sample of female twins from the United Kingdom (N = 2,752). We present novel estimates using within–identical twin and biometric models. Our findings show that one year of additional schooling is associated with about one-half year later age at first birth in ordinary least squares (OLS) models. This estimate reduced to only a 1.5-month later age at first birth for the within–identical twin model controlling for all shared family background factors (genetic and family environmental). Biometric analyses reveal that it is mainly influences of the family environment—not genetic factors—that cause spurious associations between education and age at first birth. Last, using data from the Office for National Statistics, we demonstrate that only 1.9 months of the 2.74 years of fertility postponement for birth cohorts 1944–1967 could be attributed to educational expansion based on these estimates. We conclude that the rise in educational attainment alone cannot explain differences in fertility timing between cohorts.     

Reexamining the link of early childbearing to Marriage and to subsequent fertillty

Using data from the 1980, 1985, and 1990 Current Population Surveys, we show that the link between early fertility and nonmarital births has become stronger. Women who give birth earlier are increasingly likely to be unmarried. In contrast, we find a weaker association between first births at young (versus older) ages and (1) a rapid pace of subsequent childbearing and (2) higher completed fertility. We discuss possible causes and consequences of these changes.     

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.     

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.     

Increasingly heterogeneous ages at first birth by education in Southern European and Anglo-American family-policy regimes: A seven-country comparison by birth cohort

According to the 'reproductive polarization' hypothesis, family-policy regimes unfavourable to the combination of employment with motherhood generate greater socio-economic differentials in fertility than other regimes. This hypothesis has been tested mainly for 'liberal' Anglo-American regimes. To investigate the effects elsewhere, we compared education differentials in age at first birth among native-born women of 1950s and 1960s birth cohorts in seven countries representing three regime types. Women with low educational attainment have continued to have first births early, not only in Britain and the USA but also in Greece, Italy, and Spain. Women at all other levels of education have experienced a shift towards later first births, a shift that has been largest in Southern Europe. Unlike the educationally heterogeneous changes in age pattern at first birth seen under the Southern European and Anglo-American family-policy regimes, the changes across birth cohorts in the study's two 'universalistic' countries, Norway and France, have been educationally homogeneous.