The World's Billionaires - Forbes.Com

America's most beloved investor is now the world's richest man. Soared past friend and bridge partner Bill Gates as shares of Berkshire Hathaway (nyse: BRKA - news - people ) climbed 25% since the middle of last July. Son of Nebraska politician delivered newspapers as a boy. Filed first tax return at age 13, claiming $35 deduction for bicycle. Studied under value investing guru Benjamin Graham at Columbia. Took over textile firm Berkshire Hathaway 1965. Today holding company invested in insurance (Geico, General Re), jewelry (Borsheim's), utilities (MidAmerican Energy (other-otc: MDPWL.PK - news - people ) , food (Dairy Queen, See's Candies). Also has noncontrolling stakes in Anheuser-Busch (nyse: BUD - news - people ) Coca-Cola (nyse: KO - news - people ) Wells Fargo (nyse: WFC - news - people ) Insurance operations flourished in 2007. "That party is over. It's a certainty that insurance-industry profit margins, including ours, will fall significantly in 2008." The Oracle (nasdaq: ORCL - news - people ) of Omaha issued a challenge to members of The Forbes 400 in October; said he would donate $1 million to charity if the collective group of richest Americans would admit they pay less taxes, as a percentage of income, than their secretaries. Had long promised to give away his fortune posthumously. Irrevocably earmarked the majority of his Berkshire shares to charity in 2006, mostly to the Bill & Melinda Gates Foundation. Gift was valued at $31 billion on day of announcement; donation will far exceed that sum so long as Berkshire shares continue to rise.