They aren't breaking any Olympic records. But these women continue to scale the heights. A few have even beaten out men for prominent jobs this year - Lynn Laverty Elsenhans, the new chief of Sunoco; Gail Kelly, who heads Australian bank Westpac; and Jane Mendillo, just named to run the $35 billion Harvard University endowment.

With gains, of course, come risks. The world's most powerful women are subject to the same tumultuous forces as men in high places. Economic woes claimed the jobs of Patricia Russo, who headed the troubled Alcatel-Lucent, and Zoe Cruz, former president of Morgan Stanley. Who else is in the hot seat? Keep an eye on Yahoo President Susan Decker and Israeli Foreign Minister Tzipi Livni.

Candidates for our list are globally recognized women at the top of their fields: chief executives and their highest-ranked lieutenants, elected officials and nonprofit leaders. They don't have to be rich, but they do have to wield significant influence. This year an architect, a war correspondent and the money manager of a university endowment all won spots.

We measure power as a composite of public profile - calculated using press mentions - and financial heft. The economic component considers job title and past career accomplishments, as well as the amount of money a woman controls. A chief executive is responsible for sales, for example, while a Nobel winner receives her prize money, and a UN agency head her organization's budget. We modify the raw dollar figures to allow comparisons among the different financial realms so that corporate revenue, for instance, is on the same footing as a country's gross domestic product, ascribed to prime ministers.