Carlos Slim, the telecommunications tycoon who controls Mexico's America Movil, is the richest person on Earth, according to the Bloomberg Billionaires Index, a daily ranking of the world's 20 wealthiest individuals.

The 72-year-old's net worth fell US$478.4 million ($577.7 million) in a day to US$68.5 billion as of the close of markets on Friday, as US moguls Bill Gates and Warren Buffett placed second and third on the list compiled by Bloomberg News.

Brazil's Eike Batista, who ranks 10th on the list, still covets the top spot after vowing a year ago that he'd become the world's wealthiest man by 2015.

"I'm competitive," Batista, who trails Slim by almost US$39 billion, said in a March 2 telephone interview from Rio de Janeiro. "It's Brazil's time to be No 1. Brazilians have always admired the American dream. What's happening in Brazil is the Brazilian dream and I happen to be the example." The Bloomberg Billionaires Index is updated every business day at 5.30pm in New York. Slim's fortune has increased 11 per cent this year, according to the index.

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Gates, 56, co-founder of Microsoft in Redmond, Washington, is worth US$62.4 billion, up 11 per cent year to date.

The fortune of Buffett, 81, chairman of Omaha, Nebraska-based Berkshire Hathaway, declined US$336.9 million to US$43.8 billion on March 2 and is up 2.4 per cent in 2012. Almost all of Buffett's wealth is held in Berkshire Hathaway, the company he has run since 1965.

The combined net worth of the 20 richest people is US$676.8 billion. Nine are Americans, including three from the family of Sam Walton, the founder of Wal-Mart Stores.

Number seven is Larry Ellison, 67, chief executive of Oracle, the world's third-largest software maker after Microsoft and SAP. His US$38 billion fortune puts him US$4 billion ahead of brothers Charles and David Koch, who each own 42 per cent of Koch Industries.

Batista, 55, whose investments range from iron ore to coal, is worth US$29.8 billion, up US$133.9 million on March 2. His fortune has grown 32 per cent this year, the most on the list. Sheldon Adelson, the casino magnate who owns 47 per cent of Las Vegas Sands, is number 13 with US$25.7 billion. Adelson, 78, and his family have pledged at least US$10 million to a super-PAC supporting Newt Gingrich, a Republican presidential candidate.

Liliane Bettencourt, 89, who with her family owns 31 per cent of Paris-based cosmetics company L'Oreal, is last on the ranking with US$22.4 billion.

On the rise is Gina Rinehart, the Australian mining heiress who is worth US$20.4 billion. Rinehart, 58, the daughter of the man who discovered the mines that made Australia the world's biggest iron ore exporter, inherited perpetual royalty rights to some of Rio Tinto's Hamersley mines in addition to other thermal and iron-ore deposits throughout the country.

In separate deals in the past year, steelmakers Posco and GVK Power agreed to pay a combined US$2.9 billion for pieces of Rinehart's empire.

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Mark Zuckerberg, the 27-year-old founder of Facebook, didn't make the cut. Based on a roughly US$100 billion valuation the company has been trading at in the private market, Zuckerberg's stake may be worth US$21 billion, or about 25 per cent less than previous estimates, once Facebook holds its initial public offering.

The reason: Facebook will issue more than 500 million shares of its Class B stock at the offering, diluting Zuckerberg's ownership to 21 per cent.

- BLOOMBERG