Wow -- what a year! It's unprecedented enough that we've elected an African-American president to lead the United States. But other groups that have felt marginalized in American society also made great progress in 2008. Consider women, for example.

Last year, women had reason enough to celebrate -- 12 of the 500 CEOs of the Fortune 500 companies were female. (No, not 12% -- that would be 60.) Here they are, according to Fortune as of May 2008:

  • Brenda Barnes, Sara Lee
  • Angela Braley, WellPoint (NYSE:WLP)
  • Christina Gold, Western Union (NYSE:WU)
  • Susan Ivey, Reynolds American
  • Andrea Jung, Avon
  • Carol Meyrowitz, TJX
  • Anne Mulcahy, Xerox
  • Indra Nooyi, PepsiCo (NYSE:PEP)
  • Paula Reynolds, Safeco
  • Irene Rosenfeld, Kraft Foods (NYSE:KFT)
  • Mary Sammons, Rite Aid
  • Patricia Woertz, Archer Daniels Midland (NYSE:ADM)

Since then, Safeco was taken over by Liberty Mutual, and Paula Reynolds became Chief Restructuring Officer for AIG. But in her stead, there are some new female CEOs in town. Lynn Elsenhans took over the reins at Sunoco (NYSE:SUN) in August, while Ellen Kullman took the helm of DuPont (NYSE:DD) at the beginning of 2009. And Yahoo! just named Carol Bartz, formerly of Autodesk, for its own top job. Since May, we've gone from 12 to 14 women! It's enough to make you dizzy, isn't it?

At this crazy rate of growth, adding two women per year to the total, the entire Fortune 500 will be headed by women in a mere 243.5 more years! All those male CEOs might want to start sprucing up their resumes -- in just a decade, 2% of them could get pushed out of their jobs.

That change isn't just happening at the CEO level. According to the research organization Catalyst, in 2008, women held 15.1% of board director positions, compared to 14.8% in 2007. Such a huge change!

But seriously ...
Investors have much to look forward to as women take over. As I noted in a 2004 article, a Catalyst study found that "companies with the highest representation of women on their senior management teams had a 35% higher [return on equity] and a 34% higher [total return to shareholders] than companies with the lowest women's representation." Simply put, "Top-performing companies have a higher representation of women on their leadership teams."

If you're now intrigued, look into the power of gender, and perhaps count the female faces among boards of directors as part of your stock evaluations.

Women make great investors, too. Fund analyst Amanda Kish leads our mutual fund newsletter, Motley Fool Champion Funds. Try it for free and make more from your fund investments.

Longtime Fool contributor Selena Maranjian owns shares of PepsiCo. PepsiCo and Kraft Foods are Motley Fool Income Investor selections. Western Union and WellPoint are Motley Fool Inside Value recommendations. Try our investing newsletters free for 30 days. The Motley Fool is Fools writing for Fools.