You can read the Wikipedia page on these for the actual reasons they happen[1]. It's all about Chinese local governments selling property to speculators to raise revenue and the speculators having to build to hold them rather than just sitting on the lots like regular capitalist speculators can. This does represent an inefficient use of resources but not a huge one, past ghost towns have all been filled eventually. Rapid growth covers a multitude of sins. Goodness knows what'll happen when the growth slows, as it must, but there's no particular reason to think that'll happen soon.
This is yet another way that China looks like early 19th century US. Not only are they copying industrial designs a la Samuel Slater and industrializing rapidly, they're financing local government via land speculation the way we did in the US back then. Hopefully when they have their equivalent of the panic of 1839 they'll make similar reforms.
[1]https://en.wikipedia.org/wiki/List_of_under-occupied_develop...
Otherwise, it may be able to take advantage of anti-immigrant sentiment in the developed world. That's what intrigued me about your point. China has started to invest in African infrastructure, so why not leverage that to supplement its population when the aging curse kicks in?
Perhaps because the entity is not "China", a state, but China, a culture and a specific population with a shared history etc? So arbitrarily supplementing the population as a means to keep it going doesn't make sense?
Edit: Anyway, it's besides the point: we were clearly talking about China the state (the same one that built those empty cities).
I'm only recognizing that there is a Chinese culture that has been shaped by various forces (including population migration, trade, and even war and invasion) over long historical periods (keyword: long).
Which doesn't translate to some "Since we had e.g. the Mongols in the 13th century, and they are now part of Chinese culture, it's no biggie to just get some hundreds of millions of people that don't share our culture to replace our aging population" -- any more than "Since we were subjects to the Queen before 1776 it's no biggie to subject ourselves to being a UK colony again".
>Maybe I've heard wrong, and there are in fact no substantial differences between Beijing, Shanghai, and Hong Kong
That only matters if they are also more substantial than those between "Beijing, Shanghai, and Hong Kong" to Berlin, Phoenix, Santiago, Accra or London.
Otherwise, all, or almost all, countries have regional differences within the country's culture. Beijing and Shanghai are not more different than, say, New York and Savannah or New Orleans and the Quad Cities. As for Hong Kong that has been, for over a century, shaped from being a UK colony.
At first glance your comment sounds great, yeah China is just anticipating demand, but it seems much more likely it was a wonton spending spree to help the economy continue on. With that spending spree coming to a halt, now China has millions of steelworkers, miners, construction works, etc... out of work.
Nobody is going to want to live in those cities because they want to live in established cities. Ask yourself, if the goal was to anticipate demand, why wouldn't you do all of this construction alongside established cities? Why would you often times do it in the middle of nowhere?
And the new plan going forward is to 'urbanize' already-existing places, which means building an urban center around an existing town. So it can expand outward, starting with a core of city services and administration.
You can see the same thing happening in central London, Vancouver and New York on a smaller scale. Plenty of housing in upscale neighborhoods bought as an investment and left empty.
I'd also submit that constructing buildings which never get occupied (or don't get occupied until they begin falling into a state of disrepair) is totally senseless regardless of scale.
http://www.cnn.com/2012/01/20/world/asia/china-florcruz-urba...
We have 50 MSAs with 1 million+:
https://en.wikipedia.org/wiki/List_of_Metropolitan_Statistic...
I think they aren't the right comparison either but quite a few cities are at the center of a larger built up area.
http://www.businessinsider.com/these-chinese-cities-are-ghos...
http://www.forbes.com/sites/wadeshepard/2016/04/23/chinas-la...
Sounds like they build them first then move in the people. Probably cheaper and faster that way? They do have 1.3 billion people.