The Early Origins of Birth Order Differences in Children’s Outcomes and Parental Behavior∗

We document birth order differences in cognitive and non-cognitive outcomes and maternal behavior from birth to adolescence. In the Children of the NLSY79, children of higher birth order score lower on cognitive abilities as early as age 1. The gap increases until school entry, remaining statistically significant thereafter. Mothers take more risks during pregnancy, are less likely to breastfeed and provide cognitive stimulation for latter-born children. Variations in parental behavior can explain most of the differences in cognitive abilities before school entry. Our findings suggest that a broad shift in parenting is a plausible explanation for the