CHICAGO (CBS) — The co-founder of Chicago-based Groupon is the latest local businessman to join the elite billionaires club.

Forbes magazine ranks Eric Lefkofksy as the 782nd richest person in the world with an estimated net worth of $1.6 billion. He is tied with another fellow Chicagoan, Joe Mansueto, president of the investment research group Morningstar.

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Twenty Chicagoans are on the 2011 list, which included several members of the Pritzker family, Oprah Winfrey, Sam Zell, Pat Ryan and Ty Warner.

Groupon, which has built an empire by offering daily group deals, has grown from a small start-up in 2008 to a multi-billion dollar company that recently turned down a reported $6 billion buyout offer from Google. The search engine giant is now preparing to launch a Groupon competitor, called Google Offers.

The world’s richest man, Mexican tycoon Carlos Slim, retained his crown with a fortune of $74 billion.

Microsoft co-founder Bill Gates held on to second place, growing his wealth to $56 billion. Investor Warren Buffett came in third with $50 billion.

There are about 1,200 billionaires in the world, according to Forbes.

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