Excess male mortality at early ages is an important source of child inequality in most societies. We examine how improvement in the quality of political institutions affects the male survival disadvantage. Using data on twins in combination with a natural experiment on the development of African institutions, we quantify the distinct effects of biology and preconception environment on the infant mortality sex gap and find that these effects are important only in poor institutions. The analysis implies that improved institutions constrain genetic expression and mitigate preconception influences on excess male infant mortality, which is an optimistic finding with pragmatic implications.

More than half of the HIV/AIDS-infected population today are women. We study a dynamic model of (in)fidelity, which explains the HIV/AIDS gender gap by the configuration of sexual networks. Each individual desires sexual relationships with opposite sex individuals. Two Markov matching processes are defined, each corresponding to a different culture of gender relations. The first process leads to egalitarian pairwise stable networks in the long run, and HIV/AIDS is equally prevalent among men and women. The second process leads to anti-egalitarian pairwise stable networks reflecting male domination, and women bear a greater burden. The results are consistent with empirical observations.