Description:A rising stock market and cheap money are emboldening U.S. CEO's to go after big deals. So far in 2013: $158 billion of deals. that's more than double the same period as last year according to Thomson Reuters Deals Intelligence. U.S. dealmaking contributed to a 16.5 percent rise in worldwide M&A volume. That makes it the highest level since 2007. Assistant Professor Saikat Chaudhuri of the Wharton School at the University of Pennsylvania:(2:20)