The only female head of Big Oil in the U.S., Elsenhans has made bold moves to overhaul the $37 billion refiner. Sheís sold the chemicals business and ditched three money-losing
refineries. She is relying more on retail fuels and logistics, with high returns and stable cash flows.
The list is compiled by FORTUNE editors, who consider four criteria: the size and importance of the womanís business in the global economy, the health and direction of the
business, the arc of the womanís career (resume and runway ahead), and societal and cultural influence.