On Friday, China announced its intention to relax its one-child policy, after more than 30 years. Reuters' Sui-Lee Wee and Li Hui report that the shift has been under consideration for the last five years. The complex set of family planning policies, they write, are "now regarded by many experts as outdated and harmful to the economy", due in part to an aging population.
Here's a Reuters chart showing China's dependency ratio, which compares the number of China's young and old citizens (its dependents) to the size of its working age population. A higher number means fewer working-age adults to support the young and the old.
You can also see above how big a social and economic trend urbanization has been over the last 40 years. Labor shortages have recently become a concern for Chinese leaders. It's important to note that the one-child policy change will be gradual, and that any increase in birthrates in the next few years won't lead to an increase in working age adults for at least a decade and a half.
Pew's Gretchen Livingston notes that "across Asia, even countries without a one-child policy have experienced a rapid decline in fertility rates in recent decades." Here's China's fertility rate since 1960, showing a dramatic decline before the one-child policy was implemented:
The Washington Post has an excellent rundown of the policy changes and some nifty charts on its unintended consequences. Business Insider has a chart from Nomura showing just how far outside the global norm China's male-female birth ratio is: