Mexican telecom mogul Carlos Slim Helu moved up one notch to No. 3 with $30 billion, replacing Indian steel magnate Lakshmi Mittal, who fell one place to No. 5 with $23.5 billion.

Ikea founder Ingvar Kamprad of Sweden rose two slots to No. 4 with $28 billion.

Microsoft co-founder Paul Allen edged up to sixth place from No. 7, with a net worth of $22 billion. He was followed by France's Bernard Arnault, chairman and chief executive of LVMH and The Christian Dior Group, with $21.5 billion; Arnault was new to the top 10.

Saudi Arabian Prince Alwaleed Bin Talal Alsaud fell to eighth place from No. 5, with $20 billion; and Canadian publisher Kenneth Thomson and his family moved into the top 10, ranking No. 9 with $19.6 billion.

Hong Kong's Li Ka-shing rose to No. 10 with $18.8 billion. Ka-shing is the chairman of Cheung Kong (Holdings) Ltd. and Hutchinson Whampoa Ltd.

The Walton family, which dominated the upper echelons of the Forbes list in recent years, tumbled in this year's ranking as stock in the world's largest retailer dropped more than 10 percent in the past year.

S. Robson Walton, known as Rob, who last year ranked 10th, fell to 19th with $15.8 billion. Christy Walton and Jim Walton tied for 17th with $15.9 billion each, while Alice Walton followed Rob Walton at $15.7 billion. Helen Walton, mother of the clan, did not make it into the top 20, landing at No. 21 with $15.6 billion.

Martha Stewart, who was new to the list last year, dropped off completely this year. Her fortune shrank from $1 billion to an estimated $500 million following her conviction for lying about a stock sale and her five-month prison term.

Investors in new industry sectors popped up on this year's list, most notably those with holdings in alternative energy and online gaming.

Australian Shi Zhengrong, ranked No. 350, made his $2.2 billion fortune through his solar energy company out of China. India's Tulsi Tanti, whose company owns Asia's largest wind farm, arrived at No. 562 with $1.4 billion after his company went public in October.

J. DeLeon and Ruth Parasol, both of the United States and tied for No. 428, represented the online gaming industry with $1.8 billion each. Interestingly, most of their company's revenue comes from the United States, where online gaming is illegal, Kroll said.

"Somehow, they have been able to skirt that," Kroll said.

Parasol is also one of the 10 new women to make the list and the only female newcomer to be self-made. Only six of the 78 female billionaires are self-made; most attained their wealth through marriage or inheritance.

The youngest billionaire is also female. Hind Hariri, daughter of slain Lebanese Prime Minister Rafik Hariri, is 22 years old and eight months younger than Germany's Prince Albert von Thurn und Taxis.

The methodology of the rankings remains consistent with years past, Kroll said. The magazine confirmed the worth of an individual's holdings in public companies by using the Feb. 13 closing stock price, and estimated the value of private companies by looking at comparable public firms in the industry and by consulting with experts in the field.

Forbes calculated the value of real estate by square footage minus any debt on the properties.