Michael Bloomberg

Mayor Mike has become America's 8th-richest citizen after a transaction put a solid valuation on Bloomberg LP: he borrowed to buy a 20% stake in his company from Merrill Lynch in July for $4.5 billion. Today he owns 88% of the financial data and news outfit he founded in 1982. Boston-born son of accountant got engineering degree from Johns Hopkins, M.B.A. from Harvard. Became a trader at Salomon Brothers 1970s, quit with $10 million in stock after merger. Created financial information services firm Innovative Market Systems to sell financial data, analytic tools to Wall Street. Renamed Bloomberg LP 1987; added news service, magazine, cable network, radio station. Spent $74 million to become mayor of New York City in 2001 and $85 million on reelection in 2005. Enjoying 71% approval rating, appears to be looking for ways to do away with term limits as November 2009 election looms. Since last June former Republican no longer affiliated with any political party. Has given away nearly $800 million to charity in the past 5 years; with Bill Gates, planning to invest hundreds of millions to combat smoking worldwide.