Cities were once a place for families. The “basic custom” of the American city, wrote the urbanist Sam Bass Warner, was a “commitment to familialism.” Today’s cities, however, are decidedly not for children, or for families who want children. As the sociologists Richard Lloyd and Terry Nichols Clark put it, they are “entertainment machines” for the young, rich, and mostly childless. And this development has crucial implications—not only for the future of American cities, but also for the future of the U.S. economy and American politics.

The counties that make up Los Angeles, Chicago, New York City, and Philadelphia shed a combined 2 million domestic residents from 2010 to 2018. For many years, these cities’ main source of population growth hasn’t been babies or even college graduates; it’s been immigrants. But like an archipelago of Ellis Islands, Manhattan and other wealthy downtown areas have become mere gateways into America and the labor force—“a temporary portal,” in the words of E. J. McMahon, the founder of the Empire Center for Public Policy. “The woman from Slovakia comes to Queens, lives in her second cousin’s basement, gets her feet on the ground, and gets a better apartment in West Orange, New Jersey,” he said. Or a 20-something from North Dakota moves to Chicago after school, works at a consultancy for a few years, finds a partner, and moves to Missoula.

But if big cities are shedding people, they’re growing in other ways—specifically, in wealth and workism.