We got yet more data Monday that shows that adding more women to your management team will improve your financial results. The question now is how many studies like this one we're going to need before homogeneous management teams get serious about improving the health of their businesses.

The most recent study, from the Peterson Institute for International Economics, found that the presence of more women in high levels of corporate leadership is associated with higher levels of profitability at their firms. The next most influential variable was the proportion of female board members. The presence of a female CEO appeared not to matter much. "This pattern underscores the importance of creating a pipeline of female managers," says the study.

According to this research, a profitable company in which 30 percent of the top executives are women would expect to be about 15 percent more profitable than one in which the C suite is all male. Unprofitable companies gain even more.

When it comes to the U.S., this should not surprise anyone.

  • A study by not-for-profit Catalyst found that companies with the highest representation of women on their senior management teams had a 35 percent higher return on investment and a 34 percent higher total return to shareholders than those with the least women in senior management. A study by Credit Suisse also found a link between female management and financial success.
  • An academic study back in 2003 found a positive relationship between the diversity of a company's board and its financial performance. A Catalyst study of boards reached a similar conclusion.

In the world of startups, the research is equally convincing: 

  • First Round Capital studied 300 of its investments across about 600 companies, and found that the companies that included at least one woman founder performed 63 percent better, as measured by increases in valuation, than those founded by all-male teams.
  • The Ewing Marion Kauffman Foundation showed that women-led private technology companies have a 35 percent higher return on investment than male-led ones. When they get venture money, these women-led companies generate revenue that is 12 percent higher than that of comparable male-run tech companies.
  • A study by Illuminate Ventures demonstrated that women use capital more efficiently than men.

What's different about the Peterson Institute study is its scale and scope. It surveyed 21,980 firms across 91 countries. Nearly 60 percent of these companies had an all-male board of directors. Just over half had no women in the very highest management ranks (the so-called C suite) and less than five percent had a female CEO. 

At about a third of the firms studied, or 7,859, both the board of directors and the highest executive ranks were less than five percent female. Exactly 11 companies had all-female boards and an all-female slate of senior executives.

As with other studies about gender diversity, it's hard to know if better financial results proceeded from women being in positions of power or from diversity in general. It could be that the same results could be obtained by having a leadership team that was diverse in other ways--maybe economic background, race or ethnicity, education, or geography.

It would also be interesting to take a closer look at companies that are overwhelmingly run by women. Unfortunately, among the 21,980 companies studied by the Peterson Institute, these are few and far between. Only 13 have a board of directors that is more than 80 percent women and senior management that is more than 80 percent women. So whatever we would learn from them wouldn't be statistically significant. One thing that is becoming increasingly obvious, though, is that the good-old-boy network, for all its convenience, isn't actually good for business.