China has changed its one child policy to a two child policy, but it may not do much to rejuvenate its aging population.

"It leads to a drop in the proportion of the productive labor force, which in turn raises the average wage level, making China less competitive in labor-intensive industries," Council on Foreign Relations China expert Yanzhong Huang writes in the Diplomat. "If China is approaching its Lewis turning point, a point at which China would move from a vast supply of low-cost workers to a labor shortage economy, it could quickly lose its competitive edge to other emerging economies that still enjoy significant demographic dividends."

But here's the really scary thing for China: It's not obvious that ending the one-child policy will solve its demographic crisis. The one-child policy is not, on its own, the key cause of China's graying population — those include China's growing prosperity and increasing opportunities for Chinese women outside the home. It's not obvious that repealing the one-child policy now would be able to make up for the difference.

"As UNC demographer Yong Cai has shown, today, even when fertility restrictions are lifted fertility rates don't rise," University of Maryland sociologist Philip Cohen writes in the Atlantic. "People have few children in China today because children have become too expensive—good schools especially cost too much, and the health care burdens of children outweigh the hoped-for future return of a child to care for parents when they're retired."

I have yet to hear of a country that's been able to reverse its birth rate decline with cash incentives. I hope one country succeeds just so we get a sense of the price at the indifference point.