Similarly, Princeton professor Douglas Massey studied an affordable housing development in Mount Laurel, New Jersey, that local residents had complained would lower home values, increase crime rates, and cause local taxes to rise.

He found that the development did none of those things. Many surrounding neighbors didn’t even know there was a housing project nearby.

What’s more, the lives of residents in the housing development improved markedly after they moved to the affluent suburb. An increasing amount of data seems to show that location matters just as much as income in determining a child’s likelihood of escaping poverty. As I’ve written about before, children from low-income families who move to more affluent suburbs are more likely to graduate from high school, attend four-year colleges, and have jobs than their peers who stayed in the city. And cities that have made an effort to keep schools desegregated have enjoyed less race-based strife than peer cities.

Still, affluent cities and towns often resist low-income housing projects: Despite 40B in Massachusetts, many areas of the state are falling back into the same segregation patterns that the Fair Housing Act sought to remedy nearly 50 years ago. Recent research showed, for example, that the Boston metro area has more racially concentrated areas of affluence (census tracts where 90 percent is white and wealthy) than any of America’s 20 biggest cities.