In China, traditional son preference combined with modern sex selection technology
and the one-child policy has resulted in high and rising sex ratios (males to females)
at birth since the 1980s. In 2005, 120 boys were born for every 100 girls in China,
a surplus of one million boys in that cohort alone. Unprecedented in its scale, the
social implications of a large number of men with little or no prospect of marriage are
largely unknown. In this paper, we look at crime rates, which nearly doubled in the
last two decades, and argue that male-biased sex ratios have contributed to this rise.
Using annual province-level data for the period 1988-2004, we find that a 1 percent
increase in the sex ratio raised violent and property crime rates by some 3.7 percent,
suggesting that the sex imbalance may account for up to one-sixth of the overall rise in
crime. The finding is robust to a wide range of sensitivity tests. We also show that sex
ratios have had opposite effects on men and women’s marriage market outcomes in the
expected direction and a heterogeneous effect on male labor market outcomes. Relative
to women, higher sex ratios are associated with better education and higher income
conditional on employment, but lower likelihood of being employed. This finding is
consistent with greater male-to-male competition on the marriage market having both
an incentive and a disincentive effect. Higher sex ratios may raise the private returns
to human capital investments. However, scarcity of brides can also have a disincentive
effects for those at the bottom of the barrel, whose chances of marriage are reduced
further.