CHICAGO, IL - SEPTEMBER 17:  Traders in the Standard & Poor's 500 stock index options pit at the Chicago Board Options Exchange (CBOE) react to the Federal Reserve's decision on interest rates on September 17, 2015 in Chicago, Illinois. Citing global economic concerns, the Fed chose to leave interest rates unchanged. The news was met with a round of boos in the pit. The Fed is still expected to raise rates later this year.  (Photo by Scott Olson/Getty Images)