Carol Bartz's abrupt departure from Yahoo recently was a blow to a technology industry that already has few female CEOs. But the good news is that Meg Whitman, former eBay chief, has been named CEO of Hewlett-Packard. Other women should rejoice. Why? When a female CEO heads up a major corporation, she generates opportunities for women in that company.

In a study released last month, our research group studied 112 female CEOs in 39 countries over a one-year period and found their influence has a positive impact on hiring and promoting other women. Companies led by women have more female directors in board rooms and in executive offices.

Here's what's happening in the USA:

•Six U.S. companies are listed among the top 10 firms for women globally. All are household names: Avon, Xerox, WellPoint, Pepsico, Kraft and Sara Lee.

•Last year, at 15 U.S. companies in the Fortune 500 led by women, 23% of senior executives were female compared with a Fortune 500 average of 16%.

•Two companies last year outperformed their peers in the hiring of high-level women: Western Union's former CEO Christina Gold had an executive team with five women out of 11, or 45.5%, and BJ's Wholesale Club CEO Laura J. Sen has two female executives out of five — 40%. Kraft Foods CEO Irene Rosenfeld, Avon CEO Andrea Jung and WellPoint CEO Angela Braly all have senior management teams that are at least one-third women.

•This year, the number of female CEOs at Fortune 500 companies dropped to 13, but their impact was no less dramatic. Fortune 500 companies led by American women had an average of 31% female directors on their boards compared with a 16% average in peer companies' boards.

And our global findings mirrored the influence of U.S. women at the top: Foreign companies led by women have a higher percentage of women in senior management at 25%.

Given the value that female CEOs bring to other women, it's a shame that so few of them get their shot in the business world. Too many companies are bypassing a vibrant talent pool, losing that brain power and missing out on new ideas and bold visions.

Irene Natividad is the chair of Corporate Women Directors International, a Washington-based research group.

Column: Women at top bring along other women