Birth Spacing and Sibling Outcomes PRELIMINARY AND INCOMPLETE PLEASE DO NOT CITE OR CIRCULATE WITHOUT PERMISSION

This paper investigates the effect of the age difference between siblings (spacing) on educational achievement. We use a sample of women from the 1979 NLSY, matched to reading and math scores for their children from the NLSY79 Children and Young Adults Survey. OLS results suggest that greater spacing is beneficial for older siblings, though only for low socioeconomic-status (SES) families. For high-SES families, greater spacing has no beneficial effect and is associated with lower test scores for younger siblings. However, because we are concerned that spacing may be correlated with unobservable characteristics, we also use an instrumental variables strategy that exploits variation in spacing driven by miscarriages that occur between two live births. The IV results indicate that a one-year increase in spacing increases test scores for low-SES older siblings by about 0.15 standard deviations and spacing less than two years between children decreases test scores by about 0.87 standard deviations. For younger siblings there appears to be no causal impact of spacing on test scores.