From WSJ:
During China's 30 years of economic growth, hundreds of millions of factory and urban jobs soaked up surplus rural farm labor. In the past three or four years, he says, that extra labor has been exhausted.
Many analysts predict that China's vast labor force will begin declining in the next year or two, the result of family-planning policies. Others say there's already a shortage of the most active members of the factory floor, workers aged 15 to 34. That group has been steadily declining since 2007, according to Jun Ma, Deutsche Bank's chief economist for Greater China. A shrinking work force will need higher salaries to support an expanding population of elderly.