Many of us will probably remember, however vaguely, Robert Putnam and his famous "bowling alone" thesis about the decline of social capital in the US. Some of us remember thinking that it was more about transformation and reallocation of social capital, but to make that case right now would be kind of pointless and a distraction from the work Putnam is doing now (even if it's right, which it may not be).

Putnam has just published the results of five years of research on the effects of diversity on social capital within communities (which here means neighborhoods or something similar). The conclusion: diversity reduces social capital within the community. Most striking, and most distressing, it turns out too that members of a diverse community not only trust persons of other ethnic groups less, they also mistrust others of the same ethnic background.