The impact of a Brexit would be mostly economic, not political. The “Remain” camp, which includes the leaders of the two biggest British political parties, argues that leaving the union would deal Britain a crushing economic blow. Many economists agree. And many experts also contend that a breakup of the EU could cause trouble for the rest of Europe and even the U.S. On Wednesday, Janet Yellen, chair of the U.S. Federal Reserve, cited the possibility of a Brexit as one reason for the Fed’s decision to leave interest rates unchanged. The reality is, though, that no one really knows how bad a Brexit would be, either for Britain or for the rest of the world. No country has ever left the EU, and there has never been another institution quite like it, so there are no true historical parallels. And, just as importantly, no one really knows what Britain’s relationship with the EU would look like after it left.
http://fivethirtyeight.com/features/what-a-brexit-could-mean-for-the-economy/