Cultures that favour male babies have a sex-ratio imbalance that could result in a destabilized society, researchers say.
Health care for women has improved, but the gains are offset by increases in sex-selection abortion since the mid-1980s.
"Largely as a result of this practice, there are now an estimated 80 million missing females in India and China alone," Therese Hesketh of the Institute of Child Health at University College London and Zhu Wei Xing of China's Zhejiang Normal University wrote in this week's issue of the Proceedings of the National Academy of Sciences.
"Over the next 20 years, in parts of China and India there will be a 12 to 15 per cent excess of young men," the researchers said.
In China, 94 per cent of all unmarried people age 28 to 49 are male and 97 per cent of them have not completed high school.
"In these communities, the growing number of young men with a lack of family prospects will have little outlet for sexual energy," the study's authors said in a release.
"The large cohorts of 'surplus' males now reaching adulthood are predominantly of low socioeconomic class, and concerns have been expressed that their lack of marriageability, and consequent marginalization in society, may lead to antisocial behaviour and violence, threatening societal stability and security," the study concluded.
When single young men congregate, "the potential for more organized aggression is likely to increase substantially and this has worrying implications for organized crime and terrorism," they said.
The study's authors said moves to reduce sex selection are desperately needed and should include:
- Strict enforcement of existing legislation.
- Equal rights for women.
- Public awareness campaigns about the dangers of gender imbalance.
The measures can make a difference, the pair said, noting the gender imbalance in South Korea has already declined, and gender preference data from China are encouraging.
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