An aerial view of metro Atlanta. thisisbossi / Flickr

Dense metros tend to offer more economic opportunity than less compact cities do.

For the land of opportunity, America ranks dismally low on upward mobility among the world’s developed countries. But what the groundbreaking work of Raj Chetty and others at the Equality of Opportunity Project has found in recent years is that even within the U.S., rates of upward mobility vary widely. People who live in relatively compact San Jose, for instance, have a much better chance of ascending into a higher social class over the course of their lives than people who live in, say, sprawling Atlanta.

Chetty and collaborators have found that a number of factors play a role in the upward mobility of a given metro area—residential segregation, income inequality, family stability, and school quality among them. But a brief glance at the geographical list, with San Jose and Atlanta at opposite ends, seemingly implicates urban sprawl as well. As Paul Krugman wrote, back in 2013, there’s a very logical connection between the ability to access a job and the chance to rise in the ranks:

And in Atlanta poor and rich neighborhoods are far apart because, basically, everything is far apart; Atlanta is the Sultan of Sprawl, even more spread out than other major Sun Belt cities. This would make an effective public transportation system nearly impossible to operate even if politicians were willing to pay for it, which they aren’t. As a result, disadvantaged workers often find themselves stranded; there may be jobs available somewhere, but they literally can’t get there.

The Equality of Opportunity Project has drawn a similar conclusion using commute times as a proxy for sprawl. That’s not the greatest measure: traffic can make the rush-hour work trip into Manhattan a nightmare, but no one would accuse New York City of lacking density. So a research team led by University of Utah planning scholar Reid Ewing reevaluated the sprawl-upward mobility link using a more sophisticated sprawl index that takes into account factors like density, mixed uses, activity centers, and street-network accessibility.

Their findings, published in a recent issue of the Landscape and Urban Planning, strongly support the idea that a spread-out metro area is a harmful one for social progress. (Some initial findings from Ewing and company emerged in a 2014 technical report, but the new paper elevates the work into a peer-reviewed publication.) The researchers conclude that “upward mobility is significantly higher in compact than sprawling metropolitan areas/commuting zones.”

As Krugman suspected, the direct effect of this relationship seems to emerge via job access. The more compact an area, the easier time low-income workers have finding and getting to jobs—and thus improving their social status over the long term. Ewing and company report that as their compactness index doubles, the likelihood that a child born into in the bottom income quintile will reach the top fifth by age 30 increases 41 percent; via the report:

For the average poor kid in our sample, with an 8% chance of moving up into the top quintile, this represents an increase of 3.2% in absolute terms …

The new report doesn’t list specific cities where this relationship between sprawl and upward mobility is strongest or weakest. But Ewing generously provided CityLab with data on individual metro areas, which I’ve used to create the following tables. The first two show upward mobility rates of the 10 most and least sprawled metros in the study sample (it’s worth noting that New York was not included in the data provided):

The upward mobility values represent the chance of that fifth-to-first income quintile jump described above. So in San Jose, among the most compact metros in the sample at a 128.2 index rating (the higher the rating, the more compact a metro), a poor young kid faces an 11.2 percent chance of upward mobility. And in Atlanta, the second-most sprawling metro in the sample at a 41 index rating, that same kid faces just a 4 percent chance of moving up.

The next two tables flip things around and look at sprawl or compactness in the places with the highest and lowest chances of upward mobility. There are some similarities between these lists and those above—most notably, the poor performance of Atlanta—but shifting the data in just this slight way also reveals a lot of differences:

Here we find that Provo, Utah, with its decent compact rating, boasts the best likelihood of upward mobility for poor young folks, at 14 percent. On the flipside we see that sprawling Memphis, Tennessee, has the lowest chance of upward mobility, at 2.6 percent. The regional trends on these lists are striking: nearly all the bottom 10 metros are located in the South (except Indianapolis), whereas many metros in the top 10 are found in the Mountain West or Pacific.

For good measure, here are the sprawl and mobility figures for the 10 largest metros in the study sample, measured by 2000 Census population (again, New York data wasn’t provided):

Together these lists offer a casual glance at what the new study’s more detailed analysis confirms: a strong, direct correlation between sprawl and upward mobility. Simply put, when a U.S. metro area has a high sprawl index, it tends to have a low mobility rate, and vice versa.

But the link isn’t a strictly linear one. Provo, for instance, has the top mobility rate despite a compactness index (108) that’s well off the top metro in this sample, San Francisco (152). And while Milwaukee has a pretty compact index score, at 134, it has a pretty bleak upward mobility rate, at 5.6. Such variation is a reminder that even as sprawl may have a measurable impact on a person’s economic opportunities, many other local variables influence the social ladder.

“There is clearly a need for more research to further tease out the nature of these relationships,” Ewing and company conclude. “Nevertheless, the findings of this study suggest that communities influence the chances for economic advancement of the people who live there.”

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