I came across this article on diversity and society somewhere on the City Journal. To quote:

Harvard political scientist Robert Putnam, author of Bowling Alone, is very nervous about releasing his new research, and understandably so. His five-year study shows that immigration and ethnic diversity have a devastating short- and medium-term influence on the social capital, fabric of associations, trust, and neighborliness that create and sustain communities. He fears that his work on the surprisingly negative effects of diversity will become part of the immigration debate, even though he finds that in the long run, people do forge new communities and new ties.

Putnam’s study reveals that immigration and diversity not only reduce social capital between ethnic groups, but also within the groups themselves. Trust, even for members of one’s own race, is lower, altruism and community cooperation rarer, friendships fewer. The problem isn’t ethnic conflict or troubled racial relations, but withdrawal and isolation. Putnam writes: “In colloquial language, people living in ethnically diverse settings appear to ‘hunker down’—that is, to pull in like a turtle.”

In the 41 sites Putnam studied in the U.S., he found that the more diverse the neighborhood, the less residents trust neighbors. This proved true in communities large and small, from big cities like Los Angeles, Chicago, Houston, and Boston to tiny Yakima, Washington, rural South Dakota, and the mountains of West Virginia. In diverse San Francisco and Los Angeles, about 30 percent of people say that they trust neighbors a lot. In ethnically homogeneous communities in the Dakotas, the figure is 70 percent to 80 percent.

It all makes sense, the more diverse, the less one has in common with one’s neighbors. The less one has in common, the fewer common goals, the more group competition and the payoff for community action is less. Therefore, you get less of it.

This would explain why people tend to live near people a lot like them. It would be upsetting to people who think we should all live in neatly arranged boxes supporting the “community” goals instead of our own individual ones. I think there’s lots of hugging in those boxes too.