The Federal Reserve will probably start raising interest rates around the middle of next year, two top officials at the U.S. “What we think now is that the capital markets have it more or less right but we don’t ourselves know when we’re going to do it,” Fed Vice Chairman Stanley Fischer said in Washington. The Fed has kept rates near zero since 2008 and has nearly quadrupled its balance sheet to more than $4 trillion through a series of bond purchase programs in an effort to push borrowing costs down further and boost hiring.