An interesting new study finds that children whose younger siblings are born more than two years later have higher reading and math skills than children whose siblings are born sooner. The researchers think this stems, at least in part, from the extra time the kids get during those first formative years, before all their parents’ time gets sucked up by the newborn.
Here’s the abstract:
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 positively associated with test scores for older siblings, but not 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 older siblings by about 0.17 standard deviations—an effect comparable to estimates of the effect of birth order. Especially close spacing (less than two years) decreases scores by 0.65 SD. These results are larger than the OLS estimates, suggesting that estimates that fail to account for the endogeneity of spacing may understate its benefits. For younger siblings, there appears to be no causal impact of spacing on test scores.
Interesting stuff, and it makes complete sense. Something to think about for those of you deciding if/when to have your next kid.
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