Strategy Page: China's "one child" policy (to halt population growth), and the unanticipated appearance of cheap sonograms (enabling parents to determine the gender of their child while there was still time for an abortion) has caused an imbalance in the gender ratio. There are now 115 boys for every 100 girls. Young men are having a problem finding wives. Wealthier urban males attract more women from the rural areas (where 70 percent of Chinese still live), leaving a lot of lonely, poor and angry young men in the countryside.
Lonely, poor, and angry young men won't sit around in the countryside forever.