How time flies. Steve Ballmer is now in his 13th year at the helm of Microsoft where he continues to do battle against the likes of Apple and Google. He ranks 51st in the overall countdown with an estimated $15.2 billion. Although Ballmer has refuted rumors of a forthcoming retirement announcement, part of his after-hours efforts have been focused on a campaign to move the Sacramento Kings to Seattle. The son of a Swiss immigrant, Ballmer reportedly scored a perfect 800 on his math SATs and graduated Harvard with a B.A. in Math and Economics. He joined Microsoft in 1980 through an invitation from his Harvard classmate Bill Gates.