If you subtract the 15% unoccupied rate from your link from the 6.6 gigatons of concrete, it's still a lot more than the U.S. used in 100 years.
https://www.bullionstar.com/blogs/koos-jansen/guest-post-5-c...
It does make the news when San Francisco's residents start getting driven out of the city. It does make the news when Madison limits the height of buildings downtown. Can you give me an example of people who didn't get a flat tire today? Of course not, because that's just called normal functioning.
but this only happens in the US, right? not anywhere else, like... china?
Also, china doesn't have a property tax, so you can just buy an apartment and sit on it forever, there is no economic pressure (as a property tax is) to put it to productive use.
It is speculated that China will drop the land use grant when they institute a real property tax.
Edit: looks like things have gotten worse for Ordos: http://gizmodo.com/4-instant-cities-that-are-still-completel...
If you handed out hukous in 3rd tier economically depressed new cities, I'm not sure if there would be many takers. And the properties in Kangbashi are all fairly high end anyways, the city hukou-deprived migrant workers probably wouldn't even be welcomed.
China builds a lot of subsidized public housing on the city outskirts of major cities, but no one wants to live there because transportation is bad to where the jobs are.