Diversity tends to be propagated, at least in the UK, as the cornerstone of effective workplaces, but one of the comments yesterday referenced a 2007 article from the Boston Globe about how greater diversity leads to a 'decline in social capital' [1] in communities. My reading (not sure if it's the right one, but that's one of my conclusions) from the Happiness Hypothesis [2] is that more homogenous groups tend to make people happier and easier to organise around a common goal.

Both sources go against the common narrative for diversity today in communities, but they don't write about companies.

Does anyone know of any serious studies that prove/disprove the effects?

[1] http://archive.boston.com/news/globe/ideas/articles/2007/08/05/the_downside_of_diversity/

[2] http://www.happinesshypothesis.com/