Facebook's recovery since last year's disappointing flotation has added $9.6bn to founder Mark Zuckerberg's fortune, putting him back into the top 20 in Forbes's annual rankings of America's 400 richest people.
The 2013 Forbes 400, published on Monday, puts Zuckerberg's wealth at $19bn, up from $9.4bn last year, when the tech entrepreneur slipped to number 36. The rise in Facebook's share price - which last week hit $45.30, its highest level since Facebook's botched initial public offering on May 18 last year that priced the shares at $38 but soon saw them crash to half that - has also paid dividends for Zuckerberg's former room-mate Dustin Moskovitz, who helped found the social network.
Moskovitz, 29, who is eight days younger than Zuckerberg, is the youngest billionaire in the Forbes 400. His roughly 5pc stake in Facebook, which accounts for the majority of his wealth, has increased Mr Moskovitz's net worth by $2.5bn to $5.2bn. Carl Icahn, the activist investor who last week conceded defeat in his battle to take Dell private, also had a good year, re-entering the top 20 for the first time since 2008 with gains of $5.5bn to $20.3bn. But the top 10 rankings remained unchanged, with Microsoft founder Bill Gates holding the number one spot for the 20th year running.
Gates, whose net worth has risen by $6bn to $72bn over the last year, in May overtook the Mexican telecoms billionaire Carlos Slim to reclaim his position as the world's richest man. In second place, Berkshire Hathaway investor Warren Buffett closed the gap with Gates by increasing his net worth by $12.5bn to $58.5bn, making Buffett the year's biggest dollar gainer.
Larry Ellison, the founder of software company Oracle, remains at $41bn in the number three spot, while the joint fourth-richest Americans are Charles and David Koch, the brothers behind the sprawling global conglomerate Koch Industries, who each have a $36bn fortune, up from $31bn each last year. Collectively, the 400 richest Americans have finally gained back their losses from the financial crisis.
The minimum net worth needed to make this year's list is $1.3bn - the highest entry point since property and stock market values crashed in 2008. The combined net worth of the 400 richest Americans has risen $300bn to a record $2trn, comparable to the GDP of Russia. The raised bar for entry means 61 US billionaires fall outside the top 400.
The average net worth of the members of the Forbes 400 is $5bn, the highest to date, up from $4.2bn last year. Net worth has increased for 314 members of the top 400, and decreased for 30 members. Notable newcomers to Forbes's wealth rankings include Michael Rubin, the founder of the online sports retailer Kynetics, at 243, and Robert Pera, the head of the wireless technology manufacturer Ubiquiti Networks, at 293.
Pera, 35, is one of the nine businessmen under 40 on the Forbes list. The Forbes rankings are based on a snapshot of wealth taken on August 23.