Neil G. Bennett

Is biology destiny ? Birth weight and life chances

Two key questions are addressed regarding the intersection of socioeconomic status biology and low birth weight over the life course. First do the income and other socioeconomic conditions of a mother during her pregnancy affect her chances of having a low-birth-weight infant net of her own birth weight that of the father and other family-related unobserved factors? Second does an individuals birth weight status affect his or her adult life chances net of socioeconomic status? These questions have implications for the way the authors conceive of the relationship between socioeconomic status and health over the life course specifically in sorting out causal directionality. The authors use intergenerational data from the Panel Study of Income Dynamics for the years 1968 through 1992. Results of sibling comparisons (family-fixed-effects models) demonstrate that maternal income does not appear to have a significant impact on birth weight. However low birth weight results in lower educational attainment net of other factors. These findings suggest that when considered across generations causality may not be as straightforward as implied by cross-sectional or unigenerational longitudinal studies. (authors)

Commitment and the modern union: Assessing the link between premarital cohabitation and subsequent marital stability.

In recent years, the incidence of premarital cohabitation has increased dramatically in many countries of Western Europe and in the United States. As cohabitation becomes a more common experience, it is increasingly important to understand the links between cohabitation and other steps in the process of family formation and dissolution. We focus on the relationship between pre- marital cohabitation and subsequent marital stability, and analyze data from the 1981 Women in Sweden survey using a hazards model approach. Our results indicate that women who premaritally cohabit have almost 80 percent higher marital dissolution rates than those who do not cohabit. Women who cohabit for over three years prior to marriage have over 50 percent higher dissolution rates than women who cohabit for shorter durations. Last, cohabitors and non-cohabitors whose marriages have remained intact for eight years appear to have identical dissolution rates after that time. In addition, we provide evidence that strongly suggests a weaker commitment, on the part of those who cohabit premaritally, to the institution of marriage.

The Divergence of Black and White Marriage Patterns

This article examines the patterns and determinants of first marriage among black and white women in the United States. Three major differences exist between the first-marriage patterns of black and white women: (1) lower proportions of blacks marry than whites; (2) the proportion of women who ever marry has declined substantially across cohorts for blacks but modestly across cohorts for whites; and (3) while increased education is associated negatively, if slightly, with the probability of ever marrying among whites, it is associated positively among blacks. The observed racial divergence is consistent with three factors experienced differentially by blacks and whits: the marriage squeeze, labor-market success, and out-of-wedlock childbearing. Given the traditional age differences between spouses, there are far fewer eligible male mates for black women than for white women among cohorts born before the late 1950s. For both blacks and whites, employment status is positively associated with the propensity to marry, but for young blacks the labor-market situation is generally poor and has deteriorated significantly across time in comparison with other groups. Finally, having an out-of-wedlock child at an early age is strongly negatively associated with the likelihood that a woman will ultimately marry.

The Influence of Nonmarital Childbearing on the Formation of First Marriages

We document a negative association between nonmarital childbearing and the subsequent likelihood of first marriage in the United States, controlling for a variety of potentially confounding influences. Nonmarital childbearing does not appear to be driven by low expectations of future marriage. Rather, it tends to be an unexpected and unwanted event, whose effects on a woman’s subsequent likelihood of first marriage are negative on balance. We find that women who bear a child outside marriage and who receive welfare have a particularly low probability of marrying subsequently, although there is no evidence that AFDC recipients have lower expectations of marriage. In addition, we find no evidence that stigma associated with nonmarital childbearing plays an important role in this process or that the demands of children significantly reduce unmarried mothers’ time for marriage market activities.

Birth weight and income: interactions across generations.

This paper attempts to answer a series of questions regarding the interaction of income and birth weight across generations. First, does the effect of the income of a mother during her pregnancy on her infants birth weight depend on the familys birth weight history (genetic predisposition)? Second, does the effect of low birth weight status on adult life chances depend on income during early childhood? These questions have implications for the way we envision the biological and social worlds as interacting across generations. To address these issues, this study uses intergenerational data from the Panel Study of Income Dynamics, survey years 1968 through 1992. Results of sibling comparisons (family-fixed-effects models) demonstrate that maternal income has a significant impact on birth weight for those infants who are already at high risk hereditarily (i.e., who have a low birth weight parent). However, it is not clear whether income acts as a developmental buffer for low birth weight infants as their lives progress. These findings suggest the existence of biosocial interactions between hereditary predisposition and socio-economic environment.

Mortality estimation from registered deaths in less developed countries.

Age-specific population growth rates were introduced to demographic analysis in earlier work by Bennett and Horiuchi (1981) and Preston and Coale (1982). In this paper, we derive a method which uses these growth rates to transform what may be a set of incompletely recorded deaths by age into a life table that accurately reflects the true mortality experience of the population under study. The method does not rely on the assumption of stability and, for example, in contrast to intercensal cohort survival techniques, is simple to implement when presented with nontraditional intercensal interval lengths. Thus we can obtain mortality estimates for less developed countries with defective data, despite departures from stability. Further, we assess the sensitivity of the method to violations in various assumptions underlying the procedure: error in estimated growth rates, existence of non-zero net intercensal migration, age dependence in the completeness of death registration, and misreporting of age at death and age in the population. We demonstrate the use of the method in an application to data referring to Argentine females during the period 1960 to 1970.

A census-based method for estimating adult mortality

Abstract A simple method is presented for converting an age distribution in any closed population into the stationary population corresponding to its current mortality conditions. The conversion only requires a set of age-specific growth rates, which will normally be available from successive censuses. From the stationary population, any life table mortality measure of interest can be computed. The index most robust to normal data errors in developing countries is life expectancy, and the paper focuses on its calculation. The sensitivity of results to various forms of data error is considered, and procedures are proposed for removing errors resulting from differential census coverage completeness and from age misstatement at older ages. Applications of the procedures are made to data from Sweden, India and South Korea. Because of the absence of a radix, estimation of life expectancy usually will begin at the fifth birthday.

Sex selection with biased technologies and its effect on the population sex ratio

Current biomedical research on sex selection techniques may soon offer couples the opportunity to choose the sex of their children with greater certainty. A technique planned for marketing by mid-I978 can increase the probability of bearing a son to as much as 0.90. However, couples who wish to improve their chances of bearing a daughter have no such opportunity. The purpose of this paper is two-fold. First, a decision-making model is provided which describes how couples should choose among alternative sex-selection methods so as to maximize the probability of bearing their desired number of sons and daughters. Second, the effect of the widespread use of sex-selection techniques on the population sex ratio is explored. It is shown that even if populations have unbiased sex preferences, or sex preferences biased towards daughters, the use of biased sex-selection technologies may result in very high population sex ratios.

The centenarian question and old-age mortality in the Soviet Union, 1959–1970

Are claims of extraordinarily low mortality levels in the USSR justifiable? Applying a recently developed methodology appropriate for nonstable populations to 1959 and 1970 census data from the Soviet Union, we find that mortality is generally understated for the country as a whole and for various regions and republics. This is particularly so for the republics composing the Central Asian region and the Caucasus. Age overstatement appears to be extremely pronounced in the oldest segments of the population. Using the new methodology, we can derive the age distribution that is uniquely implied by a given life table and a set of age-specific rates of growth obtained from two censuses. When we use the official Soviet life tables in this procedure, we find that the reported number of centenarians is at least 28.9 percent overstated for males and 7.5 percent for females. If one were to posit that Soviet mortality during 1959 to 1970 was, in fact, no better than the Swedish mortality experience during roughly the same time period, then the true number of centenarians could be no more than 2 percent of that reported.

Forecasting U.S. age structure and the future of Social Security: the impact of adjustments to official mortality schedules.

In this article we review the scientific literature regarding the reliability of old-age mortality rates in the United States and we address three questions related to the consequences of adopting adjustments to old-age mortality: (1) How are current and projected levels of life expectancy in the United States influenced by adjusting old-age mortality rates? (2) What is the impact of adjusted old-age mortality rates on the projected size of the older population? and (3) How would the funding of selected age-entitlement programs in the United States be affected by these adjustments?...Forecasts made using adjusted mortality schedules lead to estimates of life expectancy at birth and at older ages that over the next 60 years are lower than those published by the Census Bureau and the Social Security Administration. (SUMMARY IN FRE AND SPA) (EXCERPT)