Are first-born kids smarter?
This article investigates the link between position in the birth order and early scholastic ability. Using matched mother-child data from the National Longitudinal Survey of Youth (1979 cohort, NLSY79), I find that being the first-born is beneficial even after controlling for (nonlinear) effects of family size and child characteristics. The verbal ability of first-borns is about one-tenth of a SD higher than for children in the middle of the birth order. There is no evidence that last-borns fare better than intermediate children. The first-born advantage is confirmed by estimates from within-family variation models and I argue that the findings are consistent with the resource dilution hypothesis.
Source: “Does the birth order affect the cognitive development of a child?” from Applied Economics, Volume 41, Issue 14 June 2009 , pages 1799 – 1818
They’re also more likely to go to Harvard.