Lawrence L. Wu

Effects of family instability income and income instability on the risk of a premarital birth.

In this study I contrast hypotheses about the effects of family structure on premarital birth risks with three income hypotheses: (1) a low income hypothesis--that the risk of a premarital birth is higher for women from disadvantaged economic backgrounds because they possess fewer or less attractive economic opportunities; (2) a permanent income and transitory income hypothesis--that uncertainties generated by unexpected fluctuations in family income increase premarital birth risks net of absolute income levels; and (3) an income level and income change hypothesis--that downward trends in family income reflect worsening socioeconomic opportunities that increase premarital birth risks net of absolute income levels. I use prospective income and retrospective parental histories in the [U.S.] National Longitudinal Survey of Youth to determine if the effect of family instability...is an artifact of low unstable or declining income in the family of origin. (EXCERPT)

Race and Unemployment: Labor Market Experiences of Black and White Men, 1968-1988

This article addresses two questions: First, why is Black unemployment persistently higher than White unemployment? Second, how can this fact be reconciled with narrowing Black/White differentials in educational attainment, occupational position, and earnings? We show that the persistent racial gap in unemployment is due to differential access to employment opportunities by region, occupational placement, labor market segmentation by race, and labor market discrimination. Our findings showing that the racial gap in unemployment is greatest for college-educated men and are consistent with the view that Blacks still encounter barriers to employment in the labor market.

Parent Histories Patterns of Change in Early Life

Most studies that examine the effects of family structure have employed relatively crude measures, typically a snapshot of family intactness at age 14. In this article, we use data from the National Survey of Families and Households to examine (a) how one might better construct measures of family structure that reflect change during early life and (b) what analytical and empirical opportunities are available when the data provide a more complete parent history. We draw four conclusions. First, a substantial fraction of children have extremely diverse parental situations, even though the majority of children live in intact families. Snapshot measures understate greatly the dynamic complexities of a respondents parental situation. Second, the parent histories of respondents provide a rich but complicated set of longitudinal data and the complexity of these data makes it infeasible to adopt a data-driven approach to summarize family structure over the early lives of children. It is therefore useful to adopt a more theoretical approach in identifying salient dimensions of a respondents parent history. Third, existing theoretical perspectives conceptualize the influences of parents in markedly different ways. These contrasting views, in turn, imply quite distinct empirical measures. Finally, more informative measures of family structure may allow one to adjudicate between alternative hypotheses of family structure in ways not possible with snapshot measures.

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 of 5 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

No trend in the intergenerational transmission of divorce.

Previous studies on trends in the intergenerational transmission of divorce have produced mixed findings, with two studies (McLanahan and Bumpass 1988; Teachman 2002) reporting no trend in divorce transmission and one study (Wolfinger 1999) finding that divorce transmission has weakened substantially. Using a stratified Cox proportional hazard model, we analyze data from the National Survey of Families and Households and find no evidence for any trend in divorce transmission. To reconcile apparent differences in results, we note that the General Social Survey data used by Wolfinger lack information on marital duration, permitting analysis only for whether respondents have divorced by interview. As a result, an apparent decline in divorce transmission could be due to inadequate adjustments for the longer exposures to risk by earlier marriage cohorts, yielding a higher probability of divorce by interview for earlier cohorts relative to more recent cohorts even if divorce risks are identical across all marriage cohorts. We confirm this possibility by using a series of discrete-time hazard logistic regressions to investigate the sensitivity of estimates of trends in divorce transmission to different adjustments for exposure to risk. We conclude that there has been no trend in the intergenerational transmission of divorce.

Event History Models for Life Course Analysis

The questions posed by life course researchers often differ in fundamental ways from those posed by sociologists, developmental psychologists, or economists (Elder, 1998; Mayer & Tuma, 1990). For example, life course researchers often focus analytic attention on transitions marking adolescence or early adulthood and the roles and statuses accompanying such transitions (Hogan & Astone, 1986; Modell, Furstenberg, & Hershberg, 1976; Shanahan, 2000). Prototypical questions along these lines include whether certain social groups experience a more rapid transition to adulthood or whether the timing of such transitions (or the duration spent in selected life course statuses) has changed for successive cohorts (Winsborough, 1980). As Mayer and Tuma (1990) note, work in this vein often implicitly conceives of social structure as arising out of individual experiences of varying duration, as opposed to alternative perspectives that see social structure in terms of collectivities of persons with particular fixed attributes (Blau, 1977), as generated from relational networks (and resulting “structural holes”) among individual actors (White, Boorman, & Breiger, 1976) or from the aggregate behavior of rational actors (Becker, 1991).

Cohort Trends in Premarital First Births: What Role for the Retreat From Marriage?

We examine cohort trends in premarital first births for U.S. women born between 1920 and 1964. The rise in premarital first births is often argued to be a consequence of the retreat from marriage, with later ages at first marriage resulting in more years of exposure to the risk of a premarital first birth. However, cohort trends in premarital first births may also reflect trends in premarital sexual activity, premarital conceptions, and how premarital conceptions are resolved. We decompose observed cohort trends in premarital first births into components reflecting cohort trends in (1) the age-specific risk of a premarital conception taken to term; (2) the age-specific risk of first marriages not preceded by such a conception, which will influence women’s years of exposure to the risk of a premarital conception; and (3) whether a premarital conception is resolved by entering a first marriage before the resulting first birth (a “shotgun marriage”). For women born between 1920–1924 and 1945–1949, increases in premarital first births were primarily attributable to increases in premarital conceptions. For women born between 1945–1949 and 1960–1964, increases in premarital first births were primarily attributable to declines in responding to premarital conceptions by marrying before the birth. Trends in premarital first births were affected only modestly by the retreat from marriages not preceded by conceptions—a finding that holds for both whites and blacks. These results cast doubt on hypotheses concerning “marriageable” men and instead suggest that increases in premarital first births resulted initially from increases in premarital sex and then later from decreases in responding to a conception by marrying before a first birth.

Assessing Bias and Fit of Global and Local Hazard Models

This article assesses the bias and fit of a hazard rate model by comparing predicted and nonparametric estimates of survivor probabilities. These comparisons also generate several diagnostic displays for event history data. We illustrate these diagnostic methods for several global and local hazard models using data on age at first marriage for women from the June 1980 Current Population Survey. Our results suggest that a nonproportional local Gompertz model performs better than other models we examined.

Local Blockmodel Algebras for Analyzing Social Networks

Roles and ways of thinking about roles have been a major concern of sociologists. One common approach to roles conceptualizes and analyzes them within networks of multiple social relations (see, for example, Radcliffe-Brown, 1940; Barnes, 1954; Nadel, 1957; Mayer, 1966; Kapferer, 1969; Mitchell, 1969; Bott, 1971; Boissevain, 1973; Laumann and Pappi, 1976). A recurrent theme throughout this literature is that the fundamental variables of interest are not particular characteristics of individuals but rather the social relations that connect

EFFECTS OF EXPOSURE ON PREVALENCE AND CUMULATIVE RELATIVE RISK: DIRECT AND INDIRECT EFFECTS IN A RECURSIVE HAZARD MODEL.

This paper outlines decomposition methods for assessing how exposure affects prevalence and cumulative relative risk. Let x denote a vector of exogenous covariates and suppose that a single dimension of time t governs two event processes T1 and T2. If the occurrence of the event T1 determines entry into the risk of the event T2, then subgroup variation in T1 will affect the prevalence T2, even if subgroups in the population are otherwise identical. Although researchers often acknowledge this phenomenon, the literature has not provided procedures to assess the magnitude of an exposure effect of T1 on the prevalence of T2. We derive decompositions that assess how variation in exposure generated by direct and indirect effects of the covariates x affect measures of absolute and relative prevalence of T2. We employ a parametric but highly flexible specification for baseline hazard for the T1 and T2 processes and use the resulting parametric proportional hazard model to illustrate the direct and indirect effects of family structure when T1 is age at first sexual intercourse and T2 is age at a premarital first birth for data on a cohort of non-hispanic white U.S. women.