Sibling models of socioeconomic effects on the timing of first premarital birth.

Data on 1,000 pairs of sisters from the National Longitudinal Survey of Youth are used to estimate the effects of observed individual-level factors, common family-level variables, and shared unobserved family-level traits on the timing of premarital births. Results show a moderate correlated risk of premarital childbearing among siblings after controlling for the effects of measured covariates. The effect of older sisters' out-of-wedlock childbearing on the timing of younger sisters' premarital birth is overestimated when shared unmeasured family-level traits are ignored. Public policy measures designed to reduce premarital births have a smaller multiplier effect via reduced younger sisters' premarital births because unmeasured family-level factors are less amenable to policy measures. However, because the older-sibling effect is large when other sources of variability in premarital birth timing are controlled, interventions may be effective in reducing premarital births among young women in high-risk families.