31. THOMAS PETERFFY

$17.5  SELF-MADE SCORE: ) BILLION SOURCE: DISCOUNT BROKERAGE AGE: 75 RESIDENCE: PALM BEACH, FL PHILANTHROPY SCORE: N.A. The father of digital trading stepped down in September as CEO of Interactive Brokers, which he founded in 1993. He remains chairman of the firm, which markets a specialized trading platform to sophisticated investors. His first job at age 8 was helping his building’s superintendent stack and deliver wood to other tenants. At 12 he illegally sold Juicy Fruit gum to classmates in his native Hungary at more than double the price. He immigrated to America in 1965 at age 21.