Microsoft Corp. (NASDAQ: MSFT) Chairman Bill Gates -- net worth: $59.2 billion -- is no longer the world's wealthiest person. According to the HeraldSun, Mexico's Carlos Slim -- net worth: $67.8 billion -- now sits in that throne. In April, Slim surpassed Berkshire Hathaway Inc.'s (NYSE: BRK.A) CEO Warren Buffett as the world's second richest person. And today, Slim surpasses Gates.

How must Gates feel? I don't know. He has commented in the past that he doesn't think about being the world's wealthiest person much. But he has occupied that throne since 1995. After 12 years, there could be a twinge of regret at having lost the crown. But Gates still has plenty of money, particularly since Buffett contributed a huge chunk of his fortune to Gates' foundation.

Meanwhile how did Slim climb so fast? A 27% surge in the share price of America Movil (NYSE: AMX), Latin America's largest mobile phone operator controlled by Slim, from March to June enabled Slim to surpass Gates by $8.6 billion. The 5.7% increase in Microsoft stock in the second quarter was no match for the sharp rise in valuations of Slim's companies. He also owns shares of Telefonos de Mexico (NYSE: TMX) up 11% and Grupo Financiero Inbursa S.A. (MXK: GFINBURO) up 20%.

While I don't have earnings forecasts to evaluate Inbursa, it's not too late to consider buying in to Slim's other companies.

• American Movil. AMX's PEG of 1 -- based on a P/E of 26.2 on earnings growth of 26% to $4.22 in 2008 -- looks reasonable to me.
• Telmex. TMX's PEG of 2.5 -- based on a P/E of 12 on earnings growth of 4.9% to $3.31 in 2008 -- looks expensive to me -- I'd avoid this one.

It's not every day that a king gets dethroned. The market is sending a signal that might be worth heeding.

Peter Cohan is president of Peter S. Cohan & Associates, a management consulting and venture capital firm. He also teaches management at Babson College and edits The Cohan Letter. He has no financial interest in the securities mentioned in this post.

Warren Buffett is officially getting poorer. After just a few months as the second richest man in the world, he has been passed by Mexican telecom billionaire Carlos Slim.

According to Forbes, Slim is worth $53.1 billion and Buffett only $54.2 billion. Slim did it the hard way. He increased his net worth in the stock market. His holdings in Carso Telecom, which controls the large Mexican phone company Telmex, went up 15% and the value of his holding in wireless operator American Movil is up 4%.

The measurement means little. Slim's net worth has almost doubled in a little more than a year. The Mexican stock market is up almost 50% over that period. A slip in the economy there could easily push him back down the list. Buffett's investment in Berkshire Hathaway Inc. (NYSE: BRK..A) and Bill Gates' (No.1 on the Forbes list) holdings in Microsoft Corp. (NASDAQ: MSFT) are certainly less volatile.

Because so many of the fortunes of the people on the Forbes list are based on holdings in public companies, the list could literally be recalculated every day. The magazine may have to do that to keep up with billionaires like Slim.

Douglas A. McIntyre is a partner at 24/7 Wall St.

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