Excess Male Mortality: Between Child Biology, Preconception Environment and Institutions

Although academic investigation into sex mortality differentials dates back to the 17th century with pioneering work by John Grant, a fundamental unresolved question in demographic and public health research is the underlying causes of the higher mortality of boys in early ages. In this study, we address this question by estimating the distinct contributions of biology and unobserved preconception environmental factors to sex differences in infant mortality across institutional settings. We use a large sample of twins from sub-Saharan African countries. These countries are grouped into four main institutional regions, and each region is further divided into urban and rural areas. We find that regions with better institutions have lower levels of infant mortality and smaller sex differences in survival rates. Sex differences in biology and unobserved preconception factors contribute to excess male mortality in most institutions, but the effect of biology becomes small and statistically insignificant with improved institutions.The role played by these factors tends to be more important in settings with better institutions, which suggests that more research should be done in order to address each of them.