How did China end up with so many people?

I cannot judge this hypothesis, but I have always wondered about the question:

We hypothesize that besides technology and resource expansion, risk-mitigation improvements pushed the Malthusian limits to population growth in pre-industrial societies. During 976-1850 CE, China’s population increased by elevenfold while the Confucian clan emerged as the key risk-sharing institution for members. To test our hypothesis using historical data from 269 prefectures, we measure each region’s clan strength by its number of genealogy books compiled. Our results show that prefectures with stronger clans had significantly higher population density due to better resilience during natural disasters and fewer premature deaths of children. Confucian clans enabled pre-industrial China to sustain explosive population growth.

That is from a new paper by Zhiwu Chen and Chicheng Ma.  Via the excellent Kevin Lewis.