-Speculative buying (that's the cause of all the empty appartments in places no one wants to buy)
-Cultural reasons. When a guy wants to marry a girl, he has to own his own appartment. No when, no ifs, no but. If a girl were to marry a guy with no apartment her whole family would lose face. Because of the sex imbalance in China, there is a large "demand" of girls, and little "supply", so the "price" (quality, location and numbers of appartments) keeps rising. So this means parents of boys are constantly upping the ante, to get more and bigger appartments to try and ensure their son gets married. (my girlfriend is Chinese, so I am very aware of these issues...)
While the first reason would seem to indicate that the bubble would burst sooner rather than later, the second one seems to indicate that demand for appartment won't fall anytime soon.
Have you thought about what would happen if china lowered the marriage age for women? 50 million+ new women in the marriage market. Problem delayed.
There's already age disparity in chinese marriages. The idea that millions of young men simply won't get married is absurd. They'll just wait longer, or expand the group of women they're willing to marry.
And I assume you're joking about chinese men marrying african women.
I don't necessarily mean marrying African women (tho' why not? historically colonists have always enthusiastically intermarried) but being out of China and working on labour-intensive projects like major infrastructure. Societies with lots of frustrated young men in them tend to go horribly wrong, Afghanistan is an example, in a society where there is a shortage of women anyway due to cultural reasons (e.g. healthcare), and successful men have 4 wives, and there is no social scene for teenagers and certainly no extramarital sex, what do the young men do? They run off into the mountains and it all goes a bit Lord of the Flies.
Some of my friends (guys no less) get paid to go to clubs in China just because the owner wants to associate it as a place white people go.
You are assumed to be wealthy or at least a very good bet to eventually be wealthy.
As well, you can guarantee citizenship in a First World country. Have you encountered the term "filial piety" yet?