Courtesy of Flickr user Matthew Paul Argall, under a Creative Commons license.

Minneapolis-St. Paul is frequently held up as a place that gets right what many other U.S. urban areas get wrong. The housing is affordable. The streets are clean. Unemployment is low, and education rates are high. Even the suburbs there have historically shared their tax wealth with poorer parts of the region.

But Minneapolis-St. Paul differs from the cities to which it's compared in another important way: It's whiter than many. And if it's easier in more homogeneous places for people to rally behind the common welfare  — see Scandinavia — then Minneapolis's achievements may be more elusive in racially divided cities.

New research by political scientist Jessica Trounstine, at the University of California at Merced, suggests that a broader pattern like this exists across American cities. She's found that more segregated cities — which also typically have larger minority populations — spend less on all kinds of public goods, like roads, parks, police and sewer systems.

Why, exactly, might this happen? People are sometimes less likely to support public spending on programs they believe won't benefit them, like housing vouchers for the poor or public schools for other families' children. But here we're not talking about public spending that benefits some group of others. We're talking about spending on public goods that benefit everyone.

"This is a different kind of pattern," Trounstine says. "I’ve had people say, 'Why would people shoot themselves in the foot?' Why make your own public goods bad?'"

One theory is that whites in segregated cities have created more of their own private alternatives to public goods. They rely on private pools instead of public ones, private back yards instead of public parks, private cars instead of public transit.

"Private police? Yes. Private schools? Absolutely," Trounstine says. As diversity increases in communities, she says, so does the share of policing handled by private forces, as does the share of white children who attend private schools.

"But it doesn’t make any sense for sewers, or water," she adds. "It’s very unlikely that people are willing to spend less on sewers so they can have their own septic tank."

Which brings us back to the mystery here. Why would people in segregated cities, even controlling for income, be less likely to spend on goods that benefit everyone? Why would they spend less all together instead of just doling out those goods in an unequal way?

Trounstine's theory is that segregated cities are also more politically polarized, not necessarily along liberal-conservative lines, but along racial ones. Her research suggests that in these cities, blacks and whites are more likely to support different candidates (even if all of them are Democrats or the elections are nonpartisan). This kind of racial polarization makes it hard to create the broad coalitions you need to raise taxes, or issue public bonds or agree on big new investments in public transit.

In segregated cities, she writes in the latest paper, "the politics of space become intertwined with race." Debates over how to create a new public park become fights about whether to put it in a black or white part of town.

"It would be hard for me to tell a story from a rational point of view of whites across the U.S. thinking, ‘I am so reluctant to spend money on police forces that are going to help black neighborhoods that I’m willing to give up my own police, as well,'" Trounstine says. "It’s just a little bit far-fetched. I don’t think most white people who live in segregated cities would say that."

She goes on: "I think it’s a little bit baser than that. It's, ‘I don’t know if I want to raise a bunch of money for the schools that doesn’t seem like it’s going to be well-spent. I’m suspicious of government. I don’t like the guy who’s mayor right now.’ I think the coalition story is a more logical story."

This pattern, regardless of the exact mechanism that explains it, could have serious consequences. If cities spend less on police — as it appears that segregated places do — crime may worsen. If they spend less on fire departments, the crucial response time to emergencies could go up. Other research Trounstine is conducting suggests segregated cities have more sewer overflows. Less public spending may also mean closed libraries or public pools, or fewer investments in parks.

And given that segregated cities tend to have larger minority populations than less segregated places, that means any burdens from fewer public goods would disproportionately fall on minorities. They'd fall on the people who live in Atlanta to a greater degree than on people in Minneapolis.

Trounstine also suggests that lower spending on public goods could exacerbate inequality, especially given that lower-income families must rely on public goods (like the bus or library) when they can't afford private ones (like a car or a Curious George collection at home).

This idea ties her work as a political scientist to what economists and sociologists have told us about places like Atlanta. That segregated Southern metro, with a large minority population, often fares poorly on things Minneapolis does well, like providing opportunity for poor kids and investing in transit.

Harvard economists Raj Chetty and Nathaniel Hendren have found that more segregated places — and those with large black populations — are correlated with low economic mobility for poor kids. Other research has found that segregated metros perform worse economically if we look at income growth and property value appreciation.

It's too soon to say how all of these patterns fit together — and which might be influencing the others. But this latest research adds to the argument that segregation isn't just bad for the segregated. It might be bad for everyone.