Stephen Hemsley

If he weren’t quite so taciturn, this former accountant might be recognized as being, as Fortune called him in 2013, “the most powerful man in the U.S. health care industry.” But Hemsley is a numbers man, so let’s look at the figures: Since taking over as CEO in late 2006, he has more than doubled the company’s revenues, to a massive $147 billion in the past 12 months. He has elevated profits from just over $4 billion to a tad more than $6 billion. All the while, his company’s stock has escalated steadily upward, a total of about 130%. Hemsley’s “open innovation culture”—for example, he encourages employees to post, comment, on vote on each other’s ideas—has helped his company land on Fortune’s “World’s Most Admired Companies” list again and again. Recent improvements have been driven by the company’s technology and its data analytics arm, Optum, which has emerged as a major player. And Hemsley has predicted that Optum could eventually generate the majority of the company’s revenues.