Teams of women managing mutual funds do just as well as men, in terms of performance, but when the managers are both men and women, performance often suffers, The New York Times reports.

The conclusion is based on a report called “The Impact of Work Group Diversity on Performance: Large Sample Evidence from the Mutual Fund Industry,” conducted by Stefan Ruenzi, an assistant finance professor at the University of Cologne in Germany, and Ph.D. students at the Center for Financial Research in Cologne, Michaela Baer and Alexandra Niessen.

The researchers examined funds managed by a team at any point between 1996 and 2003, looking at the connection between the gender of team members and funds’ performance.

They found that a fund managed by four men will outperform a fund managed by three men and one woman by an average of 1.22 percentage points a year, not because of differences in capabilities between sexes but because of lack of communication. Single-sex teams, Ruenzi said, can operate more effectively.

The findings run counter to earlier academic studies that have found mixed teams to do better than single-sex teams, such as one conducted by Brown University Assistant Professor of Sociology and Public Policy E. Brooke Harrington. She believes that the two sexes working together bring added perspectives. However, her research is based on the results of investment clubs, which, Ruenzi noted, are run much more congenially than Wall Street. And fewer than one-third of team-run mutual funds have a female member of the group.

Indeed, women comprise more than 60% of the members of investment clubs, said Bonnie Reyes, president and chief operating officer of BetterInvesting, an association of investment clubs around the nation.

“The hope that simply introducing diversity will lead to better outcomes is by itself a fool’s errand,” said John W. Payne, a business professor at Duke University. “Having people with different information isn’t in and of itself enough.”

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