Mostly, I believe it's because of economic prosperity. In China, the East Coast has a lot of industry and is a major point for exports, making it wealthier than the inland regions. Just look at cities like Shanghai or Guangzhou, their buildings show how prosperous they are. This has resulted in more people moving to these cities for work, and fewer people remaining in the rural areas. The demographic differences are quite clear because of this.
Mostly, I believe it's because of economic prosperity. In China, the East Coast has a lot of industry and is a major point for exports, making it wealthier than the inland regions. Just look at cities like Shanghai or Guangzhou, their buildings show how prosperous they are. This has resulted in more people moving to these cities for work, and fewer people remaining in the rural areas. The demographic differences are quite clear because of this.