By Sharon LaFraniere

April 10, 2009

BEIJING — A bias in favor of male offspring has left China with 32 million more boys under the age of 20 than girls, creating “an imminent generation of excess men,” a study released Friday said.

Diego Azubel/European Pressphoto Agency

For the next 20 years, China will have increasingly more men than women of reproductive age, according to the paper, which was published online by the British Medical Journal. “Nothing can be done now to prevent this,” the researchers said.

Chinese government planners have long known that the urge of couples to have sons was skewing the gender balance of the population. But the study, by two Chinese university professors and a London researcher, provides some of the first hard data on the extent of the disparity and the factors contributing to it.

In 2005 , they found, births of boys in China exceeded births of girls by more than 1.1 million. There were 120 boys born for every 100 girls.

This disparity seems to surpass that of any other country, they said — a finding, they wrote, that was perhaps unsurprising in light of China’s one-child policy.

They attributed the imbalance almost entirely to couples’ decisions to abort female fetuses.

The trend toward more male than female children intensified steadily after 1986, they said, as ultrasound tests and abortion became more available. “Sex-selective abortion accounts for almost all the excess males,” the paper said.

The researchers, who analyzed data from a 2005 census, said the disparity was widest among children ages 1 to 4, a sign that the greatest imbalances among the adult population lie ahead. They also found more distortion in provinces that allow rural couples a second child if the first is a girl, or in cases of hardship.

Those couples were determined to ensure they had at least one son, the researchers noted. Among children born second, there were 143 boys for 100 girls, the data showed.

The Chinese government is openly concerned “about the consequences of large numbers of excess men for social stability and security,” the researchers said.

But “although some imaginative and extreme solutions have been suggested,” they wrote, China will have too many men for a generation to come.

They said enforcing the ban against sex-selective abortions could normalize the sex ratio in the future.

The study was conducted by Wei Xingzhu, a Zhejiang Normal University professor; Li Lu, a Zhejiang University professor; and Therese Hesketh, a University College London lecturer.

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