Under Hollub’s leadership, Occidental outperformed the market in 2017 despite depressed oil prices globally, with shares up more than 25% year over year. Since becoming CEO in 2016, she’s focused on cost cutting, and her strategy seems to be working: After losing $574 million in her first year at the helm, the energy explorer turned a $1.3 billion profit last year. Hollub also pushed for an expansion of Occidental’s operations in the Southwest’s Permian Basin, growing revenue 29% to $13.3 billion last year.