They say that a good man is hard to find. But in some countries, the opposite is true: a good woman is hard to find—because it’s hard to find women at all. According to a recent article by the BBC, the Chinese city of Lianyungang has eight men for every five women. Ninety-nine cities in China have gender ratios as high as 125 (125 men for every 100 women, or a 5:4 ratio).

But China is not alone. India has a gender ratio of 113, and the ratio in Asia as a whole is 104.4. In the United States, by contrast, the rate is 97, meaning that there are more women than men.

Gender imbalances are caused by cultural and economic preferences for male children, which contribute to sex-selective abortion and female infanticide. Over 60 million girls are “missing” in Asia as a result of these practices.

Furthermore, some government policies may intensify these gender preferences. China’s one-child policy, for example, may cause concern among parents, particularly in rural areas, that having a female child endangers their family’s future. Government policies intended to combat skewed gender ratios, such as bans on prenatal ultrasounds for the purpose of determining the baby’s sex and bans on sex-selective abortion, have proven ineffective.

Unbalanced gender ratios have consequences that reach beyond just the mothers and children involved. According to Valerie Hudson, high gender ratios leave many men without prospects for marriage, which may mean these men have fewer incentives to contribute peacefully to society. The men with the slimmest prospects for marriage are likely to be unemployed, poor, and uneducated, so they are already at increased risk for violent behavior. Hudson cites statistical evidence showing links between high gender ratios and higher rates of violent crime, drug use, trafficking, and prostitution.

Hudson and co-author Andrea den Boer cover these links in greater detail in their book Bare Branches: The Security Implications of Asia’s Surplus Male Population. In the 11th issue of the Environmental Change and Security Report, Richard Cincotta takes issue with some of the statistical methods that Hudson and den Boer use. He argues that what is important is not nationwide gender ratios, but the number of “marriage-age men” (25-29 years old) and “marriage-age women” (20-24).

While there may be some debate over whether the relationship between gender ratios and violent behavior is a causal one, there is little doubt about what causes the gender imbalances in the first place. An end to preferences for female children will be beneficial not only to girls and women, but to societies as a whole.

Photo Credit: A subway in China, courtesy of flickr user 俊玮 戴.