The world\'s richest people lost a combined $32.8 billion last week as concerns over a possible Greek exit from the euro area pushed the Standard & Poor\'s 500 index to its biggest weekly loss since November 2011. Mexican Carlos Slim, 72, lost the most during the week, as shares of his Mexico City-based telecommunications company America Movil SAB fell 4.38 per cent. Slim, who lost $4.1 billion (Dh15 billion), remains the world\'s richest person with a $65.5 billion fortune, according to the Bloomberg Billionaires Index. Facebook co-founder Mark Zuckerberg, 28, became the 26th richest person after the world\'s most popular social network raised $16 billion in an initial public offering on May 17. The company\'s shares stalled in their public debut on Friday, rising 23 cents above the IPO price of $38. Zuckerberg is worth $19.4 billion. \"Given the hype and excitement, people expected it to be a lot higher,\" Herman Leung, an analyst at Susquehanna Financial Group, said in a telephone interview from his San Francisco office. \"This is similar to Google. The company will not get the benefit until they start proving themselves as a public company.\" The S&P 500 fell 4.3 per cent to 1295.22 during the week as Greece failed to form a government and Moody\'s Investors Service downgraded 16 Spanish banks, citing a recession and mounting loan losses. The S&P 500 is down almost nine per cent since April 2. Bill Gates ranks second on the index with a net worth of $59.1 billion — $6.4 billion behind Slim. Gates\'s nest egg dropped 4.4 per cent as shares of Redmond, Washington-based Microsoft fell 5.45 per cent during the week. Berkshire Hathaway chairman Warren Buffett, 81, is the third richest person in the world. His fortune fell $1.1 billion to $44.6 billion. On May 17, Berkshire agreed to pay $142 million for Media General\'s 63 community-focused newspapers. \"I think there is a future for newspapers that exist in an area where there\'s a sense of community,\" Buffett said at Berkshire\'s annual meeting in Nebraska on May 5. Berkshire shares fell 2.4 per cent last week. Most of the fortunes of Zuckerberg\'s Facebook co-founders remained unchanged Friday in New York trading. Dustin Moskovitz, 27, who started Face-book with Zuckerberg from their dorm room at Harvard University, owns 133.7 million shares of the company\'s Class B stock worth $5.1 billion. Eduardo Saverin, 30, has a $2 billion stake. According to a regulatory filing dated Thursday, he owns 53.1 million shares of the company. Co-founder Christopher Hughes, 28, fell short of becoming a billionaire. He owns about 22 million shares of Facebook, according to a person familiar with his holdings who asked not to be named because the matter is private. His stake is worth $840 million. Hughes, who bought the Washington, DC-based magazine the New Republic in March for less than $5 million, has more than $100 million in cash and real estate after selling some of his Facebook hoard, according to data compiled by Bloomberg. Sean Parker, who persuaded Zuckerberg to move to California to focus on the company full time in 2004, owns 66 million Facebook shares worth $2.5 billion. Facebook\'s chief operating officer Sheryl Sandberg, 42, who was lured from Google in 2008, owns 27 million shares, including 25 million restricted stock units that have vested. They are valued at $1 billion.The net worth of LVMH Moet Hennessy Louis Vuitton chairman Bernard Arnault was lowered $15 billion on the index on Thursday because of the way he owns his stake in the world\'s largest luxury-goods company. France\'s richest man, 63, controls 46.5 per cent of LVMH\'s share capital, according to the 2011 annual report of the Paris-based luxury goods maker. That figure includes 5.55 per cent of LVMH shares held by Arnault, and a 40.9 per cent stake of the company owned by publicly traded Christian Dior. Arnault only owns 70.4 per cent of Christian Dior, according to French regulatory filings. The remaining 29.6 per cent of Dior is held by outside investors. While he controls all the voting power of Dior\'s stake in LVMH, his economic interest is less than the figure reported in the LVMH annual report. Arnault\'s new net worth calculation represented the biggest wealth re-evaluation since March 5, when Bloomberg began tracking the fortunes of the world\'s richest people daily. He is worth $23.5 billion. The Bloomberg Billionaires Index takes measure of the world\'s wealthiest people based on market and economic changes and Bloomberg News reporting. Each net worth figure is updated every business day at 5.30pm in New York and listed in US dollars.