I spent ~2 years in mainland China (Zhengzhou, where iPhones are assembled). The number of 15+ story apartment buildings along major freeways was astounding -- all of them seemingly empty.

When in China I was told this is driven by a combination of two things:

1. The average person in China does not believe in investing in intangible assets. This means the stock market is not appealing, so they all pile into the best physical investment around -- housing.

2. Owning your home and a car before marriage is considered 'mandatory' in traditional Chinese culture (for men). If you forego this you have what's known as a 'naked wedding' -- not good. Renting doesn't count.

Excess housing means the average rental yield (rent / property cost) is so low that it's not worth finding tenants. Examples include $300k condos renting for ~200 USD / month.