Chicago Mercantile Exchange board members Jack Sandner, Leo Melamed, chairman Terry Duffy, CEO Craig Donohue and vice-chairman Charlie Carey (L to R) ring the opening bell on the agriculture floor of the Chicago Board of Trade building on the first official trading day of the newly formed CME Group on July 13, 2007. On Monday, shareholders at the CBOT voted to accept the bid of the CME to join the two exchanges and create possibly the world's largest exchange, the CME Group, in a deal valued at $11.9 billion. (UPI Photo/Brian Kersey)