It still seems to me that you're working backwards from your hypothesis a little. For example, that Wikipedia article doesn't even have PPP numbers from before

It still seems to me that you're working backwards from your hypothesis a little. For example, that Wikipedia article doesn't even have PPP numbers from before 1980, when birth rates first started to decline (again, likely due to the reproductive education campaign). You're doing a post hoc ergo propter hoc thing here. China's GDP increased dramaticaly, China's birth rates decreased dramatically afterwards, therefore birth rates decreased because GDP increased. In order for your claim to stand you at least have to narrow it significantly to "birth rates in China went through the floor once poverty decreased past a certain point", otherwise you have to explain why birth rates didn't subsequently fluctuate inversely with GDP. Further, you also would have to explain why male births so dramatically outnumber female births. But I think more concretely, the timeline doesn't match. China didn't get above $1000 PPP until ~1990, and at that rate their birth rates should still have been very high [1]. However they'd been under 3 for 10 years at that point [2]. It's much simpler to say that China told people how to not have kids in 1970, the one/two child policies held the birth rate down subsequently, and couples took drastic measures to predominately have male children while also staying under the limit in order to satisfy a sexist culture. That's a more direct, parsimonious, and complete explanation, whereas the GDP argument has to also show why the reproductive education campaign and one/two child policies did effectively nothing, why birth rates fell dramatically before the Chinese people saw significant economic development, and why couples worked very hard to primarily have male children--work that weirdly also had no influence on the birth rate. [1]: https://en.wikipedia.org/wiki/Income_and_fertility https://en.wikipedia.org/wiki/Income_and_fertility [2]: https://en.wikipedia.org/wiki/Demographics_of_China#Table_of_births_and_deaths_1950%E2%80%932019 https://en.wikipedia.org/wiki/Demographics_of_China#Table_of...