The importance of being earliest: birth order and educational outcomes along the socioeconomic ladder in Mexico

We study the effect of birth order on educational outcomes in Mexico using 2 million observations from the 2010 Census. We find that the effect of birth order is negative, and a variety of endogeneity and robustness checks suggest a causal interpretation of this finding. We then examine whether these effects vary across households’ economic status, and we find significant heterogeneity across absolute as well as relative standards of living, operationalized as household wealth and relative deprivation. Finally, we find that firstborns’ advantage is amplified when they are male, and in particular when other siblings are female.