Economically, I never understood the one-child policy. Sure, feeding a billion people is hard. But curbing your population because you don't want to feed them, in a labour-based economy, is like burning cash because you don't want to deal with finding a storage locker for it.China will face a double hit, thanks to the legacy effects of the one-child policy
China was trying to clear out the peasants. As you mechanize farming your labor needs plummet so those become idle, angry males with nothing better to do than foment revolution. When you're trying to pivot from agrarian to industrial economy, limiting idled farmers is a prudent move. China also grossly understated its population problems. They probably peaked between 1.3b and 1.5b people, not 0.9 and 1.1.