But the biggest story on the list was the surge in the wealth of Facebook founder Mark Zuckerberg, whose fortune has jumped from $US2 billion to $US6.9 billion thanks to recent revisions of the value of the social media giant.
But the increase in Facebook's value has cost Zuckerberg the title of America's youngest billionaire. That badge now belongs to Facebook co-founder Dustin Moskovitz, who was born eight days after Zuckerberg and has a fortune of $US1.4 billion.
While the US economy might be struggling to click into gear, the Forbes list suggest the country's wealthiest entrepreneurs have enjoyed a big boost in the last 12 months.
The total wealth of the group increased 8% to $US1.37 trillion, compared with $US1.27 trillion last year. The 10 richest members of the list, who lost a stagging $US40 billion last year, increased their fortunes by $24.9 million.
In total, 217 of the entrepreneurs on the list increased their wealth, while 84 experienced falls. In 2009, 314 members of the list saw their wealth decline.
There was no change to the members of the top 10 list, although there was some change in the order.
Gates' wealth increased $US4 billion to $US54 billion, while Buffett's fortune increased $US5 billion to $US45 billion.
Oracle founder Larry Ellison remains in third spot with his wealth unchanged at $US27 billion. Christy Walton, one of the many heirs to the Wal-Mart fortune, is the highest placed woman with $US24 billion.
Rounding out the top five is controversial manufacturing and chemicals billionaire Charles Koch, who along with his brother David (ranked sixth with an identical fortune of $US21.5 billion), have donated heavily to conservative politics in America.
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