Research suggests that companies with prominent female leadership produce strong financial performance. That makes diversity an important criterion when sizing up potential investments. This year's awards from Catalyst, an organization that studies women in leadership, honored three promising prospects: McDonald's (NYSE: MCD), Kaiser Permanente, and Time Warner (NYSE: TWX).

Big progress
Women occupied half of the senior executive positions at health care's Kaiser Permanente by 2009; racially or ethnically diverse women held 18% of them. Thanks to a companywide diversity initiative, its board of directors went from 21% women in 2001 to 36% women in 2009. That's quite an accomplishment, especially in an industry with atypically high levels of women in charge. Aetna's (NYSE: AET) board is 29% female, while UnitedHealth's (NYSE: UNH) is 22%, versus the national average of 15.7%.

Thanks to its own diversity push, McDonald's has boosted its percentage of women restaurant managers around the world. Women's representation rose from 27% to 35% between 2006 and 2009 in the Asia-Pacific, Middle East, and Africa region; from 45% to 52% in Europe; and from 62% to 64% in the U.S. The percentage of women on McDonald's board of directors also climbed from 14% to 23%. In contrast, Yum! Brands (NYSE: YUM), which includes Pizza Hut, KFC and Taco Bell, has just one woman among its 12 board members (8%).

Between 2003 and 2009, Time Warner worked to strengthen its employee development programs and to accelerate the development of all its leaders, women included. The percentage of women in executive management rose from 18% to 23%, while those in the executive pipeline grew from 37% to 42%. The company's board features two women out of 13 directors (15%). In contrast, News Corp. (Nasdaq: NWS) sports one woman among 17 directions (6%), though Disney (NYSE: DIS) has four out of 13 (31%)

Performance matters
We can't know exactly what percentage of these' companies returns are attributable to these initiatives, but studies suggest that greater gender diversity is linked to outperformance.

The S&P 500 has struggled to break even over the past five and 10 years. However, McDonald's has performed much better in the past five years than it did from 2001 to 2006, and outperformed those numbers by a much greater degree over the past five years than over the past 10, suggesting an improvement in performance. The fast-food giant's operating margin and return on equity have also been considerably higher over the past few years than they were in the early 2000s.

Time Warner's financial performance has been bumpier, and its shares haven't done nearly as well, but the company has at least stopped the bleeding in its stock price during recent years.

Companies with diverse leadership benefit from differing points of view. According to research by McKinsey, female leaders are especially good at promoting development and spurring achievement among their workforces. Other studies suggest that boards with more women lead organizationally stronger companies that are better at weathering economic crises. The winners above show us how the right plan can yield big improvements in diversity in relatively little time. When seeking winners for your portfolio, companies that embrace diversity and empower all their workers are a great place to start.

Walt Disney and UnitedHealth Group are Motley Fool Inside Value choices. Walt Disney and UnitedHealth Group are Motley Fool Stock Advisor selections. Motley Fool Options has recommended a diagonal call position on UnitedHealth Group. The Fool owns shares of UnitedHealth Group and Yum! Brands. Try any of our investing newsletter services free for 30 days.

Longtime Fool contributor Selena Maranjian owns shares of McDonald's, Yum! Brands, and Time Warner. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is Fools writing for Fools.