Here we are in 2011, and how odd is it that only a dozen Fortune 500 companies have female CEOs?

This despite plenty of evidence that placing women in key positions pays off for investors.

Maybe it’s coincidental — at least it’s worth noting — that two of the Dow 30 companies that delivered the best stock-market gains in 2010 are run by women.

One is Dupont , whose CEO, Ellen Kullman, was profiled by my colleague Carol Loomis in last year’s Fortune 500 issue. Since taking charge at DuPont in January 2009, Kullman has reversed decades of moribund performance and dismal results.

Indeed, the 48.1% pop in DuPont’s shares last year was second-best, behind Caterpillar’s 64.3%, on the Dow. (Tractors and backhoe loaders, you can’t get more macho than that.)

Kullman and the bosses at Caterpillar (CEO Douglas Oberhelman succeeded Jim Owens as CEO last July) have been at their companies for decades. (Hmm, maybe outsider CEOs are overrated.) The Dow’s other winning woman, by measure of 2010 stock-market performance, is almost a lifer at Kraft Foods . But Irene Rosenfeld needed a brief stint at PepsiC0 , running Frito-Lay, to collect the cred to become Kraft’s chief executive in 2006.

Revamping Kraft has been a mighty challenge for Rosenfeld. For one thing, a shareholder named Warren Buffett threw cold water on her $19 billion acquisition of candy maker Cadbury a year ago. But she persisted and prevailed. Kraft shares rose 15.9% last year (vs. the Dow’s 11% average gain). Investors who reinvested dividends got a 20.5% return.

Meanwhile, No. 1 on Fortune‘s Most Powerful Woman list, PepsiCo CEO Indra Nooyi, eked out a 6.4% stock-market gain. More work to do in 2011. One tactic up her sleeve: paying big money for Pepsi to sponsor The X Factor, the Simon Cowell-backed talent competition show that will go up against American Idol — starring Coke — this fall.