$53.5 billion

Telecom, Mexico.

Telecom tycoon who pounced on privatization of Mexico's national telephone company in the 1990s becomes world's richest person for first time after coming in third place last year. Net worth up $18.5 billion in a year. Recently received regulatory approval to merge his fixed-line assets into American Movil, Latin America's biggest mobile phone company.

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#2 Bill Gates

$53 billion

Microsoft, U.S.

Software visionary is now the world's second-richest man. Net worth still up $13 billion in a year as Microsoft shares rose 50% in 12 months, value of investment vehicle Cascade swelled. More than 60% of fortune held outside Microsoft; investments include Four Seasons hotels, Televisa, Auto Nation. Stepped down from day-to-day duties at Microsoft in 2008 to focus on philanthropy.

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#3 Warren Buffett

$47 billion

Investments, U.S.

America's favorite investor up $10 billion in past 12 months on surging Berkshire Hathaway shares; says U.S. has survived economic "Pearl Harbor," but warns recovery will be slow. Shrewdly invested $5 billion in Goldman Sachs and $3 billion in General Electric amid 2008 market collapse. Recently acquired railroad giant Burlington Northern Santa Fe for $26 billion.