The Washington Post notes a recent report from the Chinese government.  It says:

This month, officials released what they said was their first "population development strategy research report," assembled by hundreds of scholars. That report credited China's national family planning policy with preventing the birth of more than 400 million people over the last 30 years.

The policy has also contributed to an imbalanced sex ratio; allowed only one child, many couples choose to abort female fetuses, in keeping with the traditional preference of the Chinese for boys. According to the population report, there are 118 boys for every 100 girls, and the gap is expected to grow. By 2020, if the current birthrate remains stable, marriage-age men will outnumber women by 30 million, a "serious hidden danger which may lead to social disorder," the report said.

To read more:

http://www.washingtonpost.com/wp-dyn/content/article/2007/01/23/AR2007012301392.html?referrer=email