The former Chairman of the U.S. Federal Reserve, Ben Bernanke, suggested in 2004 that over the preceding 10 to 15 years, many modern central banks became relatively adept at manipulation of the money supply, leading to a smoother business cycle, with recessions tending to be smaller and less frequent than in earlier decades, a phenomenon termed "The Great Moderation" This theory encountered criticism during the global financial crisis of 2008–2009. Furthermore, it may be that the functions of the central bank may need to encompass more than the shifting up or down of interest rates or bank reserves: these tools, although valuable, may not in fact moderate the volatility of money supply (or its velocity).