This is the VOA Special English Economics Report.
 
Facebook is the world's biggest social network. It has over nine hundred million users worldwide. And it reported three point seven billion dollars in sales for last year. 
 
The company has been privately held since two thousand four. That was when Mark Zuckerberg and several classmates at Harvard University started Facebook as a business. But on May eighteenth, Facebook becomes a publicly traded company. That means its shares will be listed on the NASDAQ stock exchange, and sold to the public.    
 
Interest in the stock has been building since Facebook announced details of its initial public offering, or IPO, earlier this year. The IPO will make billionaires of the company's founders, including Mr. Zuckerberg. Eduardo Saverin, a co-founder, has been strongly criticized for giving up his United States citizenship. He will avoid a fifteen percent tax on the value of his shares by claiming to be a citizen of Singapore.