Robert Putnam..... has found that the greater the diversity in a community, the fewer people vote and the less they volunteer, the less they give to charity and work on community projects. In the most diverse communities, neighbors trust one another about half as much as they do in the most homogenous settings. The study, the largest ever on civic engagement in America, found that virtually all measures of civic health are lower in more diverse settings. Link
This information can be used for evil ends with racism being an example. But diversity just for the sake of diversity never made a lot of sense to me. I think when relating with anyone there has to be something that is sacred which is shared to bridge the gap or it will never work. The Catholic Church is diverse in the many types of people that belong to the faith. It is truly universal but it only works with Christ being the corner stone. What will be the cornerstone for America as it becomes more diverse?