“U.S. central bankers not only regularly leak secret information about monetary policy, but the leaks are so predictably timed that a savvy investor without access to the leaked information could make money just by buying stocks in certain weeks. The weeks that have excess stock-market returns are generally the same in which there are closed Fed Board meetings, and increased volatility in short-term interest-rate futures contracts suggests that it is information on monetary policy from those meetings that is driving the pattern.”
http://in.reuters.com/article/2015/11/22/usa-stocks-fed-leaks-idINKCN0TB01120151122