According to the three authors of a study relating to team empowerment and effectiveness, "whereas laboratory findings often support diversity benefits…field research tends to show more negative effects." Trying to sort out why, they conducted a large, in-depth study of "four organizations (two Fortune 500 organizations and two smaller companies) that had formally implemented teams in the…United States." The companies were textile manufacturers, a high-tech firm, and an insurance company. More than 1,000 team member surveys and 101 leader surveys (from 112 teams) were supplemented by on-site interviews of 98 teams.
Of all the kinds of diversity tested—including age, gender, and time in the company—only one was related to level of empowerment: the more racially diverse the team, the less likely it was to be empowered. Also, more racially diverse teams rated themselves as less effective, as did their team leaders, but other kinds of diversity did not change those ratings. Further analysis of the numbers showed that the relative lack of empowerment of the racially mixed teams explained the lesser effectiveness. When team leaders were of a different race from their members, they gave those teams less power and rated them as less effective—although the teams' ratings of their own effectiveness were not related to the race of their boss.
Racially balanced or mostly minority teams led by whites made up 41%, and balanced or mostly white teams led by minorities were 18%. The study report did not separate out the results for white and minority leaders. The only other significant difference between respondents was that team leaders with longer time in the company rated their teams lower (regardless of race) than did leaders with shorter tenures.
So teams that were more racially diverse, and those that differed more in race from their team leaders than did others, were less likely to be empowered to make their own decisions by those leaders, which in turn made them poorer performers. The study was not designed to determine what caused the race effects. Nor did it test effectiveness through some objective means such as costs or output, which could have clarified whether opinions of lower effectiveness were only that: opinions.
Trying to stay objective, the researchers point out that "segregating employees by race into teams is not likely to be accepted in any organization that promotes and values diversity." They also point out that increasing diversity in the trained workforce "require(s) organizations to aggressively recruit and hire minorities." The solutions they suggest are:
The authors offer two warnings. First, the "efficacy of diversity training…has received little attention by researchers," which is to say that it has not been scientifically proven (or disproven). Second, noting that "diversity consultants attempt to sell the idea that diversity in groups will result in positive outcomes," they say these "purported benefits of team diversity may be overly optimistic…" and "may not carry over to the work teams on shop floors or back offices…" Source: Kirkman, B., P. Tesluk, and B. Rosen (04), "The Impact of Demographic Heterogeneity and Team Leader-Team Member Fit on Team Empowerment and Effectiveness," Group & Organization Management 29(3):334.