"We often get asked how reliable are our numbers," said Luisa Kroll, senior editor for Forbes. "It's our job to figure out who are the people that are trying to pump up their numbers and who are the people that are trying to hide their numbers."

Of the 1,210 billionaires on this year's list, 648 saw their net worth increase and 160 saw their net worth decrease. There were 214 newcomers to the list in 2011, including Mark Pincus, founder of San Francisco-based Zynga Game Networks Inc., creator of FarmVille.

The $4.5 trillion held by billionaires on the Forbes list represents about 2.3% of the world's wealth. The Credit Suisse Research Institute, based in Zurich, estimated the world's households had about $195 trillion in assets last year.

U.S. Dominates

No one region dominated the rankings. The U.S. had the greatest representation, with 34%, followed by the Asia- Pacific region with 27%.

"This year, the United States is still number one but the lead is shrinking," said Forbes. Ten years ago U.S. residents accounted for about 50% of the list, he said. "The trend is very real."

The Standard & Poor's 500 Index returned 15% in 2010, compared with a 1.9% loss for the Euro Stoxx 50. India's Sensex Index returned 19% for the year and Hong Kong's Hang Seng Index gained 8.6%.

Arnault's Wealth

The wealthiest European, Bernard Arnault, 62, chairman and chief executive of LVMH Moet Hennessy Louis Vuitton SA, the world's largest maker of luxury goods, jumped to fourth from seventh as his net worth increased $13.5 billion to $41.0 billion. LVMH announced Monday it will acquire a controlling stake in Bulgari SpA, the world's third-largest jeweler.

Larry Ellison, 66, chief executive officer of Oracle, Corp., rose to fifth this year from sixth in 2010. Ellison's net worth increased $11.5 billion to $39.5 billion as shares of his firm returned 43% as of Feb. 14. Redwood City, Calif.-based Oracle Corp. is the world's second-largest software maker.