The cause and effect is not so clear. China's wealth has also risen substantially, and with it comes fertility decline. E.g. India reached below replacement fer

The cause and effect is not so clear. China's wealth has also risen substantially, and with it comes fertility decline. E.g. India reached below replacement fertility a couple of years ago without it. I think it's likely the one child policy contributed a bit, but a substantial part of the decline is clearly also due to economic development.