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

In this paper we study birth order effects on educational outcomes in Mexico using 2 million observations from the extended questionnaire section of the 2010 Census. We find that birth order effects are 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 first-borns’ advantage is amplified when they are male, and in particular when other siblings are female.