Origins of sex imbalance in early age mortality: is it biology, environment, or parental preferences?

Roland Pongou, Brown University

We propose a methodology that decomposes sex differences in mortality into the effects of pre-birth environmental factors, child biology, and parental preferences. Exploiting variation in sex differences in mortality among twins and within male-female twin pairs, and variation in gender bias in sub-Saharan Africa and India, we show that : (1) prebirth environmental factors account for a large fraction of the usual excess mortality rates of male children; (2) the biological make-up of male children contributes to this excess mortality only during infancy, but its effect has been previously overstated; (3) parental discrimination against female children in India negatively affects their survival; but failure to adjust for pre-birth and biological effects leads the conventional methodological approach to understate its effect by 160 percent during infancy, and 33 percent during childhood.