For the second time in a week, Paul Krugman has castigated urban sprawl. First, he blamed Detroit’s bankruptcy on “job sprawl,” when in fact many other factors are to blame and Krugman got his numbers wrong. Now he says Atlanta’s entrenched poverty is due to urban sprawl. “The city may just be too spread out,” he says, “so that job opportunities are literally out of reach for people stranded in the wrong neighborhoods.”

Krugman quotes the Equality of Opportunity Project, whose research found that one of many factors correlated with lower social mobility was “areas in which low income individuals were residentially segregated from middle income individuals.” But income segregation is very different from sprawl, and can take place in communities of any density. New York City, for example, has pretty high economic segregation.

Krugman adds that Atlanta’s sprawl “would make an effective public transportation system nearly impossible to operate even if politicians were willing to pay for it, which they aren’t.” He obviously doesn’t know the history of mass transit in Atlanta, which had a great transit system until regional leaders decided to build an expensive rail transit system. Since they aimed the rail lines at suburbanites and sacrificed bus service to inner-city neighborhoods to pay for rail construction, transit’s share of commuting has fallen by more than 60 percent and per capita transit ridership has fallen by more than two thirds.

Only 7 percent of Atlanta households lack a motor vehicle, and only 3.7 percent of Atlanta-area workers live in households that lack cars, which are both less than the national average. So jobs are not really out of reach to most people regardless of income. Krugman might argue that low-income people in Atlanta are forced to own cars because of sprawl, but for most people cars cost less and provide far better mobility than transit, so this is irrelevant.

The Equality of Opportunity Project found that economic mobility is low throughout the South (except Texas), not just in Atlanta. But the differences in the unit measured—the percentage of children in the bottom fifth of incomes who end up in the top fifth–are small, ranging from 4 percent in Atlanta to 11 percent in San Jose. Moreover, what differences there are appear to be unrelated to sprawl: Chicago, a fairly dense area, is almost as low as Atlanta, while Pittsburgh, a fairly low-density area, is almost as high as San Jose.

The study lists a lot of factors that seem to correlate with low economic mobility, but none of them are related to population density or sprawl. The most important factors appear to be tax rates, racial residential segregation, K‑12 school quality, and the percentage of single-parent families. The South scores particularly high on racial residential segregation and low on K‑12 schools, which together go much further toward explaining its relatively low economic mobility than urban sprawl.

Residential income segregation, which Krugman focuses on, is only one of several other factors mentioned by the study, and far from the most important one. Even if sprawl were one of the factors, the study itself notes that “all of the findings in this study are correlational and cannot be interpreted as causal effects.” By blaming low economic mobility on sprawl, Krugman is relying on fabricated evidence while ignoring the real problems.

As it happens, the Daily Beast has just published a report by Joel Kotkin and Wendell Cox on Aspirational Cities, which they describe as cities with economic growth and a high quality of life. The majority of cities on their list are in the South, where people are moving to take advantage of new economic opportunities.

It is sad that some local residents, who may be victims of historic racial segregation, poor schools, and one-parent families, aren’t able to take advantage of these opportunities. But these problems did not result from urban sprawl. On the other hand, the factors that Kotkin & Cox say provide a higher quality of life and economic growth–minimal land-use regulation, low traffic congestion, and high housing affordability–are in fact positively correlated with sprawl.

Why is Krugman suddenly pandering to the anti-sprawl community? Back in 2005, Krugman correctly identified anti-sprawl policies as the cause of the housing bubble. He must be aware of research showing that minority homeownership rates are higher in sprawling regions than compact ones (mainly because housing is more affordable in the former than the latter). All else being equal, including quality of schools and racial segregation, sprawling areas are likely to have more social mobility than more expensive, compact areas.