His research focuses on the effects of social contexts on health and fertility, and on how social environments and policies affect families and children. Recent studies include cross-national comparisons of fertility trends and health disparities, how welfare participation and mental health affect marriage, and the effect of neighborhood racial composition on birth outcomes. His current projects focus on the measurement of social networks and neighborhoods, changes in immigrant health over time spent in the U.S., explaining trends in teen fertility, and the role of prenatal care on successive fertility.