Bill Gates lost the top position as the richest man to Warren Buffet an American investor who runs Berkshire Hathaway stock.

The price of Berkshire Hathaway stock increased pushing Buffet's fortune to an estimate of $62 billion, higher than $10 billion last year, taking him ahead of Microsoft co-founder Bill Gates, who maintained his former position as the richest man in the world for 13 consecutive years.

Gates is currently worth $58 billion and is ranked the third world richest, but $2 billion higher than last year.

Gates may have been richer had Microsoft's bid to acquire Yahoo been successful.

Microsoft shares dropped by 15 percent between Jan. 31, the day before the firm announced its bid for the search engine giant, and Feb. 11, the day stock prices for 2008 World's Billionaires list were locked.

Mexican telecom tycoon Carlos Slim Helu became the second richest man with an estimated net worth of $60 billion.

Class A shares of Berkshire Hathaway increased by 25 percent from mid-July and the stock increased as high as $150,000 a share in December, making Buffet worth about $65 billion by that time.

Microsoft shares also increased by 30 percent between late October and early November to $37 a share, but declined sharply after the firm announced its intentions to buy Yahoo for $45 billion.

Stock in Slim's most significant holding, telecom outfit America Movil has increased by 120 percent since the beginning of 2006.

Slim also owns stakes in Carso Global Telecom, Grupo Carso and Grupo Financiero Inbursa.

Buffet is a son of a Nebraska politician, and used to deliver newspapers as a boy.

Buffet filed his first tax return at the age of 13, and wanted a $35 deduction for his bicycle, before moving to study under value investing Guru Benjamin Graham at Columbia University.

Buffet started buying shares in textile firm Berkshire Hathaway way back in 1962 and bought a controlling stake in 1965, before starting to buy insurance companies and investing those companies' cash reserves.

Berkshire currently has investments in insurance, jewelry, utilities and food and has some non-controlling stakes in Anheuser-Busch, Coca-Cola and Wells Fargo.