The early origins of birth order differences in children's outcomes and parental behavior

We document birth order differences in cognitive and noncognitive outcomes and maternal behavior from birth to adolescence using the National Longitudinal Survey of Youth 1979 (NLSY79). As early as age one, later-born children score lower on cognitive tests than their siblings, and the gap increases until school entry and remains statistically significant thereafter. Variations in parental behavior, such as cognitive stimulation by mothers, can explain a large portion of the birth order differences in cognitive abilities before school entry. Our findings suggest that broad shifts in parental behavior are plausible explanations for the observed birth order differences in education and labor market outcomes.