3. James Simons, Ph.D.

It’s not his money that makes Simons powerful. It’s his genius—and how he uses it. He just happens to be a billionaire as well. Even better, he is a self-made billionaire who climbed his way onto the Forbes 2010 World’s Billionaires List at No. 80 with a net worth of $8.5 billion. To put this in perspective, Donald Trump ranks at No. 488 with a net worth of $2 billion and Oprah ranks at No. 400 with $2.4 billion. Simons is the mastermind of a time-tested investment strategy that helps to keep his company, Renaissance Technologies, from losing ground. Simons cracked codes for the U.S. Department of Defense during the Vietnam War, and when Wall Street was spiraling downward, Simons’ disciplined investment strategies kept his firm moving forward. His Medallion Fund surged 80 percent in 2008, despite the market collapse. But Simons is not just a billionaire, he’s a philanthropist and scholar. He funds scientific research and co-founded the charitable Simons Foundation with his wife, Marilyn. And like a truly powerful person, he does it all under the radar.