Courtesy of Flickr user David Wilson under a Creative Commons license.

In strictly economic terms, sprawl is inefficient. Spread people out, and it takes them longer to drive where they need to go, and it costs them more in gas money to get there. Disperse a few people over a lot of land, and that land is used inefficiently, too. Then give those people roads and sewers — you’d need a lot more of both to serve 20 households living over a square mile than 20 on the same block. And that's to say nothing of the costs of fire and police service when people live far apart.

These costs add up, in both private budgets and public ones. It’s a messy thought exercise to contemplate tallying them, akin to trying to calculate the productivity America wastes by sitting in traffic every year. How do you measure, for instance, the saved health care costs in a community where many people walk for transportation every day? How do you quantify the pleasure gained from a big yard that offsets any of these costs?

So take this number as more of a starting point than a final answer: A new analysis authored by Todd Litman at the Victoria Transport Policy Institute concludes that sprawl costs the U.S. economy more than $1 trillion every year.

More than half of that, Littman calculates as part of a New Climate Economy research project lead by the London School of Economics, is borne by people living in sprawling places who have to drive more, among other things. About $400 billion of it is borne by other people, in the form of air pollution or traffic congestion, or costlier public services — all of it created not necessarily by consumer demand for big homes and lots of driving, but also by policies in America that encourage and subsidize sprawl.

"An awful lot of auto travel and sprawl is the result of market distortions," Litman says. He's talking about policies like the home mortgage interest deduction that encourages large, suburban housing, as well as the fact that we don't charge people for the true costs of using roads. In a more efficient market, he says, "consumers would rationally choose to own fewer automobiles, to drive less, to rely more on walking, cycling and public transit, and they’d choose more compact home and work locations simply because that really optimizes everybody’s benefits."

His $1 trillion number is based on a tremendous number of assumptions. And they’re grounded in a particular take on what the opposite of sprawl should look like. Litman asks the question of what would happen if everyone living in metropolitan America (cities and their suburbs) lived at a density of about 10 people, or five households per acre. That’s by no means Manhattan. It’s a number that represents today about the top fifth of urban density in America.

“For the most part, it means that families with children would have a house with a yard,” Litman says.

You can parse the math behind his big number. It doesn’t include the costs in lower social mobility for children growing up in the most sprawling metros. It doesn’t take into account the higher housing costs many families would pay if they moved closer to the city, or the price tag if we built the kind of public transit we’d need to support a denser population. Economic modeling is by definition imprecise — all the more so when we’re modeling a matter like land use that influences everything from the air we breathe to our quality of life.

But Litman’s underlying point is a valid one: The costs of sprawl are vast, too, and they’re often externalized. At a much larger scale, they will certainly be borne by the planet if the 2.2 billion people in the world projected to move into urban areas in the next several decades live in the equivalent of American suburban sprawl. Today, density in American metropolitan areas is a fraction of what it is in many other global metros:

Litman
Litman, Bertraud

The optimal density Litman uses in the report is only about 23 people per hectare. Add those 2.2 billion people to global cities at a density of about Atlanta, and we'd need the equivalent of all the land in India to accommodate them. Around 23 people per hectare, though, the picture looks quite different:


Litman

The urbanization the world is undergoing right now is unprecedented. In 1950, 746 million people worldwide lived in urban areas. Today, that number is 3.9 billion.

"Frankly, that can be a wonderful thing," Litman says. "It can make everybody better off if we do this right. We can increase economic productivity, and increase social equity, and increase environmental protection if we do it correctly."

But there's a lot of evidence we're not currently doing that, in the U.S. and elsewhere.