And as several recent papers have argued, the modern high earner, with his or her long hours — and, more often than not, a working partner rather than a stay-at-home wife — is willing to pay a lot more than the executives of yore for a central location that cuts commuting time. Hence gentrification. And this is a process that feeds on itself: as more high earners move into urban centers, these centers begin offering amenities: — restaurants, shopping, entertainment — that make them even more attractive.

We’re not just talking about the superrich here, or even the 1 percent. At a guess, we might be talking about the top 10 percent. And for these people, it’s a happy story. But what about all the people, surely a large majority, who are being priced out of America’s urban revival? Does it have to be that way?

The answer, surely, is no, at least not to the extent we’re seeing now. Rising demand for urban living by the elite could be met largely by increasing supply. There’s still room to build, even in New York, especially upward. Yet while there is something of a building boom in the city, it’s far smaller than the soaring prices warrant, mainly because land use restrictions are in the way.

And this is part of a broader national story. As Jason Furman, the chairman of the White House Council of Economic Advisers, recently pointed out, national housing prices have risen much faster than construction costs since the 1990s, and land-use restrictions are the most likely culprit. Yes, this is an issue on which you don’t have to be a conservative to believe that we have too much regulation.

The good news is that this is an issue over which local governments have a lot of influence. New York City can’t do much if anything about soaring inequality of incomes, but it could do a lot to increase the supply of housing, and thereby ensure that the inward migration of the elite doesn’t drive out everyone else. And its current mayor understands that.

But will that understanding lead to any action? That’s a subject I’ll have to return to another day. For now, let’s just say that in this age of gentrification, housing policy has become much more important than most people realize.