The perception that a city has reached its maximum population and nobody else should be allowed in, or nothing should be allowed to change, is limiting the potential of our cities and increasing housing inequality.

Emily Badger of The Washington Post's Wonkblog tackles the question of how we determine when a city just can't take any more people by comparing our densest cities with those around the world, and discovering we're not necessarily as dense as we think. Further, an increase in population in one area results in economic and environmental benefits.

"Put more and more workers in one place, meanwhile, and you also get buzzing hubs like New York's Garment District or Boston's biotech corridor, where people working on the same problems bump into each other and share ideas and suppliers and become more productive. Put more people in a city, and the economy grows. It's the opposite of diminishing returns. The environmental costs, per person, can actually improve. In drought-stricken California, some of the lowest water consumption per capita is in San Francisco."1

Urban areas are defined globally as continuously "built up" land within a labor market. They are typically larger than cities but smaller than metropolitan areas.

LAST month, in response to the news that Detroit's white population is now growing for the first time in decades, with the number of residents surging in particular downtown, a local radio station paused to ask: "Is Detroit big enough for everyone?"

It was an odd question, given that the city's population is less than half the size it was in 1950, with tens of thousands of empty lots and hollow homes attesting to the ample elbow room. If any community in America has space — crannies to tuck new housing, capacity to absorb more ideas and bodies — it is Detroit.

Echoes of a similar suspicion to the contrary, though, are widespread in how we talk about the places where we live. The entire city of San Francisco is "cooked. Done." There's no more room in Silicon Valley, either. Brooklyn is at capacity. Boston, too. The nicest parts of Northwest Washington long ago reached the limit. Chicago's coveted Lincoln Park wants fewer people. Even whole countries now suffer from this condition: Britain just can't take in any of those refugees because the island, at long last, is full.

Built into these arguments is a powerful but slippery contention: It is possible to fill up a place.

We seldom question the premise because it sounds absolute, measurable, even mathematical. I'm sorry, it's not that I don't want you to move here. It's just that we are already full.

....

William Fischel, who has long studied land use at Dartmouth, has some fascinating theories of what changed in the 1970s. For one, the national Environmental Protection Act empowered local residents worried about the environmental cost of new development. But the 1970s were also a time when we began to think of our homes not just as places to live, but as financial investments for the future.

And people who believe their homes will put their children through college, or fund their retirement, are bound to be more protective of them.

"That’s when people began to look around and say 'well what might threaten the value of this home?'" Fischel says of the 1970s. Residents were no longer worried about the old-school zoning concerns of keeping factories and housing apart. "They worried about 'well, if there’s another housing development down there, it’s going to crowd the schools, and create more traffic.' They became hyper-sensitive to community effects. And they started showing up in zoning hearings."

It's gauche to talk about property values at a public meeting, Fischel says, but the concerns people voice instead are clearly connected.

In his new book, "Zoning Rules!" Fischel cleverly uses a Google Ngram, which tracks the frequency of words in digitized books, to follow the rise of our obsession with housing values against the surge in interest in limiting growth. We've reproduced his experiment here:

....

This new attitude over the last 30 years has layered atop an American instinct that has always been here.

"It was part of the original promise that if you come from Europe to the U.S., you get your own space, with your own home, and it’s a private home, and it’s got elbow room from your neighbors," says Hirt, the Virginia Tech urban planning expert who has written a new book on the history of American zoning.

There's a deep-seated cultural perception of space in America, that we should all have a lot of it, that a town with a family per acre can be full. And it's not just because we have a big country; they have a lot of land in Russia, too, Hirt points out. Their cities are still much denser.

Of course, what's based on culture and politics – not physics — can change. So maybe we can learn to live differently.

“Everybody that lives in San Francisco thinks that San Francisco is the once-and-always great place," says McCarthy, head of the Lincoln Institute. "I was in San Francisco in 1971 and it wasn’t that great. It was actually in very bad shape."

The city was losing population then, and it took many years to recover. Now we think million-dollar micro-apartments are the norm.

"But 40 years from now, San Francisco might look like Detroit. And it might look like Detroit because people have decided to stop evolving and adapting," McCarthy says. "And instead we move around on the planet instead of making the places that we care about work.”