What is Houston doing right that Atlanta isn’t?

The question may seem strange to those who know neither city well, since at first glance there is not much to distinguish the two from each other.

The latter has been called the Capital of the South, the former is the South’s largest city. Both are booming Sun Belt towns, home to concentrated poverty as well as newly built suburban mansions. They share a love of laissez-faire, southern-style government and low taxes (not to mention barbecue). And neither has a particularly large downtown to speak of; instead, the office parks and shopping malls sprawl along the highways as far as the eye can see.

But there’s a key difference: if you’re a child growing up in Houston and your parents are in the bottom fifth of wage-earners, you are twice as likely to end up in the top 20 percent of society than if you had grown up in Atlanta.

That’s what researchers at Harvard and Berkeley concluded in a study of tax policies across America, which has been getting national attention since its release.

Atlanta, which finished dead last among large urban areas, has come under particular scrutiny thanks to Paul Krugman’s column in the New York Times.

Calling it a city “stranded by sprawl,” Krugman argues Atlanta’s low density and lack of regulation for commercial development are major reasons that children who grow up there aren’t upwardly mobile, since the way the city is laid out makes it difficult for working-class residents to get to their jobs.

But what about Houston? By some measures, Texas’s largest city sprawls more than Atlanta. Its total area is more than half the size of Rhode Island.

Yet Houston ranked relatively well in the Harvard-Berkeley study, finishing in about the middle of the pack of major American cities in ensuring upward mobility for its poorest children.

From a geopolitical standpoint, Houston also defies another major implication of the study: that children who grow up in most parts of the South are less likely to experience upward mobility.

It’s impossible to know for sure, of course. But a look at some of the statistics used by the Harvard-Berkeley researchers points to a few key differences between the two cities that may play a role in their ability to ensure social mobility.

The lessons we can draw from those differences aren’t limited to the South; they can also improve our understanding of what drives the cities most able to provide bright futures for their children.

1. A Diverse Population

Both Atlanta and Houston are rapidly expanding metropolises, and ethnic minorities are playing a major role in this expansion in both cities.

But one remarkable statistic from the data used by the Harvard-Berkeley researchers is just how much more ethnically diverse Houston is than Atlanta.

According to the authors, about 20 percent of residents in Houston’s “commuting zone” are foreign-born, mainly Latino but also with significant numbers of Asian immigrants.

That’s almost twice as high as the figure for the Atlanta area, which is just under 11 percent.

The impact that the presence of an employed immigrant class has on a city’s culture and commerce—much less social mobility—is hard to measure. But consider this: according to a study by the noted urban theorist Richard Florida, cities with larger immigrant populations tend to have higher wages, greater economic output, and more innovative and diversified economies.

Florida’s finding held true even for cities whose immigrants are largely “low-skilled”—a category that comprises 43 percent of the foreign-born residents of the Houston area.

Houston’s immigrant community is especially well-established, too. Of those who weren’t born in this country, the number who entered the United States over twenty years ago is about the same as those who entered in the last ten years.

While we shouldn’t assume immigrants necessarily have a causal effect, the more prosperous economic environment that occurs alongside their presence in Houston could go a long way toward ensuring upward mobility when compared with neighbors like Atlanta.

2. A Stable Population

Whether Houston’s residents are immigrants or not, when they arrive, they tend to stay put.

That’s another significant difference the city has with Atlanta, according to data from the Harvard-Berkeley study.

This factor, called “migrant inflow/outflow,” was another of the several dozen statistics the report’s authors took into account.

To measure it, they determined the percentage of the urban area’s population that filed a tax return in a different county in 2004 than in 2005.

As it turns out, the population of the Atlanta area is much less stable than that of Houston. About 12 percent of Atlanta residents left one of the metro area’s counties between those two years, while just 5.5 percent left a Houston-area county. The “inflow” figures for the two had a similar discrepancy.

Though we shouldn’t extrapolate too much from just two years’ worth of data, it’s clear while both metropolitan areas are growing rapidly, they are growing in very different ways. During that time in Atlanta, people were either moving to a different county within the metro area, or leaving the metro area entirely, at a rate twice that of Houston.

The data aren’t specific enough to know which situation is more common, but either case suggests a level of community instability that’s detrimental to civic engagement. And civic engagement, the Harvard-Berkeley study found, closely correlates with strong income mobility.

3. A Political Structure That Promotes Cooperation

Where minority and immigrant populations are concerned, population stability can also affect the political culture of a metro area.

In Atlanta, a half-century of white flight has virtually guaranteed tension between the suburbs, most of which are majority-white, and the city, which is majority-black.

Exacerbating this tension is the fact that most people who live in the Atlanta area don’t live in Atlanta: only 8 percent of metro residents call the city home. Fulton County, in which most of Atlanta is situated, has one million people, but there are three suburban counties each with more than 600,000 residents.

Houston certainly experienced white flight as well. But 36 percent of the region’s residents still live in the city proper, mostly because the city is just so sprawling. And Harris County overall has ten times as many people as the next-largest county in the metro area.

This means that, instead of the geographic division found in Atlanta, no one race dominates politics in any important jurisdiction in Houston. Residents of all ethnicities and classes are forced to work together in local government.

This has practical implications when it comes to city services. Take public transit, for example. METRO, the Houston-area bus and light-rail provider, counts 57 percent of Houston residents in its sprawling service area. MARTA, the agency in Atlanta, serves just 27 percent of its metro residents, since majority-white suburban counties refused to join it in a 1971 referendum.

Comprehensive public transit means better access to jobs, which in turn goes a long way toward enabling upward mobility. And it’s the result of a political structure in Houston that, intentionally or not, promotes rather than discourages unified regional policymaking.

4. Inexpensive Colleges—and Lots of Them

If there’s one factor above all that can help lead to upward mobility, though, it’s access to a college education. College graduates on average make 77 percent more money over the course of their lives than workers with just a high-school diploma. They also benefit from a lower unemployment rate overall.

It’s no secret, however, that tuition costs are increasing exorbitantly, making a degree less and less affordable for many people living in America.

Given this reality, the last point from the Harvard-Berkeley study on which Houston and Atlanta differ is in some ways the most remarkable: the Houston area has a much larger number of colleges that aren’t very expensive to attend.

The statistic analyzed the percentage of colleges and universities in each city’s “commuting zone” with tuition fees at or below the twenty-fifth percentile nationally. Houston, as it turns out, has almost four times as many such institutions as Atlanta.

Local Differences, National Lessons

The findings of the Harvard-Berkeley study are by no means definitive, and its authors have cautioned against reading too much into their findings.

Nevertheless, the statistics behind the report are a good jumping-off point to figure out what specific steps metro areas can take to promote mobility. After all, both Atlanta and Houston have sprawled in every possible direction.

Only one seems to remember which is the way forward.