Causes and consequences of skewed sex ratios

Slightly more males are born in the world than females. But because male mortality is usually greater, in old age groups there are many more women than men. The situation is particularly stark in the former Soviet Union—where male adult death rates are exceptionally high. In much of Asia, strong son preference has long informed unusually high female child mortality. And the impact of this on sex ratios has been reinforced by the recent spread of sex-selective abortion. Especially in China, there are an unusually large number of boys relative to girls. Sex ratios are also skewed by migration—most notably, male labor migration. Unbalanced sex ratios have many effects. Among other things, research has focused on the consequences of male outmigration for those who are "left behind," and the implications of the coming heightened masculinity of young adult populations in Asia—e.g. with respect to marriage and crime.