Now comes word that diversity as an ideology may be dead, or not worth saving. Robert Putnam, the Harvard don who in the controversial bestseller "Bowling Alone" announced the decline of communal-mindedness amid the rise of home-alone couch potatoes, has completed a mammoth study of the effects of ethnic diversity on communities. His researchers did 30,000 interviews in 41 U.S. communities. Short version: People in ethnically diverse settings don't want to have much of anything to do with each other. "Social capital" erodes. Diversity has a downside.But note that in his entire study, Prof. Putnam could find only one exception: evangelical megachurches!
For a book-length treatment of the history and concept of diversity, see Diversity: The Invention of a Concept by Peter Wood.