Hanna Rosin's Atlantic piece on section 8 vouchers - and the suburbanization of violent crime - is well worth a read. It's a case study in unintended consequences. Money quote:

In the most literal sense, the national effort to diffuse poverty has succeeded. Since 1990, the number of Americans living in neighborhoods of concentrated povertymeaning that at least 40 percent of households are below the federal poverty levelhas declined by 24 percent. But this doesn’t tell the whole story. Recently, the housing expert George Galster, of Wayne State University, analyzed the shifts in urban poverty and published his results in a paper called “A Cautionary Tale.” While fewer Americans live in high-poverty neighborhoods, increasing numbers now live in places with “moderate” poverty rates, meaning rates of 20 to 40 percent. This pattern is not necessarily better, either for poor people trying to break away from bad neighborhoods or for cities, Galster explains. His paper compares two scenarios: a city split into high-poverty and low-poverty areas, and a city dominated by median-poverty ones. The latter arrangement is likely to produce more bad neighborhoods and more total crime, he concludes, based on a computer model of how social dysfunction spreads.

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