> “If you want to get rich, build roads first; have fewer children, plant more trees.”

Having fewer children followed "naturally" as child mortality dropped and women's education and workforce participation rose. You can quite clearly see China's birth rate dropping before the one-child policy was enacted:

* https://www.pewresearch.org/short-reads/2015/11/20/will-the-...

* https://populationmatters.org/news/2021/06/chinas-changing-c...

Even India, which has also been growing in prosperity, has seen a declining fertility rate without a heavy handed government policy:

* https://archive.is/https://www.economist.com/china/2015/07/1...