In the popular cities which is where everyone wants to live, it's quite low.
They've been full for quite a while, turns out land in desirable places is not infinite and there's no supply. So don't increase demand by allowing wealthy foreigners to buy out everything.
The inability to build fast mass transit is what keeps this so true. High speed rail into nearby towns could / should change the amount of land available but nobody builds it except the Chinese. And Americans don’t even consider it
That's what "full" means in practical terms. Obviously the parent doesn't mean "the entire city is a contiguous matrix of one-cubic-meter boxes, each with a person inside". People will have different opinions on whether it's "full", of course, based on how much they are willing to fundamentally alter the nature of the location, traffic, desirability, etc.
This is true of every location, of course. Major metros are just where the population, and acceptance of density, is highest, so it's the obvious example to look at.
> So don't increase demand by allowing wealthy foreigners to buy out everything.
I’m not sure about the effect of “wealthy foreigners” since if they are wealthy they are probably competing for more expensive properties that your school teacher or grocery store worker aren’t.
But you’re on to something here which isn’t being addressed which is the effect of mass migration to some of these countries. Obviously the migrant workers too want to and gravitate toward the cities with the most jobs, which would place additional pressure on housing prices since they join an already hyper competitive pool of buyers.
They've been full for quite a while, turns out land in desirable places is not infinite and there's no supply. So don't increase demand by allowing wealthy foreigners to buy out everything.