" Thomas A. Kochan, a professor at MIT’s Sloan School of Management, has probably researched corporate diversity more extensively than anyone. His conclusion after a five-year study? “The diversity industry is built on sand.” Prof. Kochan initially contacted 20 major companies that have publicly committed themselves to diversity, and was astonished to find that not one had done a serious study of how diversity increased profits or improved operations. He learned that managers are afraid that race-related research could bring on lawsuits, but that another reason they do not look for results is “because people simply want to believe that diversity works.”
Like other researchers, he found “the negative consequences of diversity, such as higher turnover and greater conflict in the workplace,” and concluded that even if the best managers were able to overcome these problems there was no evidence diversity leads to greater profits.
“The business case rhetoric for diversity is simply naive and overdone,” he says, noting that the estimated $8 billion a year spent on diversity training did not even protect businesses from discrimination suits, much less increase profits.
Common sense suggests that it is hard to get dissimilar people to work together. Indeed, a large-scale survey called the National Study of the Changing Workforce found that more than half of all workers said they preferred to work with people who were not only the same race as themselves, but had the same education and were the same sex. "

― Jared Taylor , White Identity: Racial Consciousness in the 21st Century