I've been living in Beijing for the past two years now and one thing I can't seem to figure out, even though I've discussed it with Chinese and non-Chinese people alike, is why the hell there are so many people in this country.
The most common reason put forward is that Chinese adults had a lot of children in order to help out on the farm. But to me this doesn't hold because the US was a farming nation for a long time, and one that is just as big as China, and we have 1/4th of their total population. Also considering China's less than ideal history for population growth (in the 20th century alone the they have had famines, genocides,civil wars, purges,invasions, etc) it is astonishing that they have continued to grow unaffected.
So how does China have such a ridiculously large population? Do they just have absurd amounts of unprotected intercourse to make up for their severe population loses? That's literally the best answer I can think of.