Quantitative Easing is a type of expansionary monetary policy that a central bank may engage in when the traditional tools of monetary policy are insufficient to address economic conditions. The central bank engages in quantitative easing in order to increase the money supply, perhaps to encourage investment and consumption in a liquidity trap scenario or when faced with the zero bound problem. In ordinary times, the central bank increases the money supply by buying U.S. government bonds from private bondholders. The Fed pays cash for these bonds, so after the transaction there are fewer bonds and more dollars present in the economy, increasing the money supply. When bond purchases fall short of the monetary expansion the Fed desires, it engages in quantitative easing by purchasing other types of assets, such as corporate bonds, from institutions such as banks. Japan pioneered quantitative easing in the early 2000s to fight deflation, and the U.S. Federal Reserve conducted several rounds of quantitative easing to combat the Great Recession between 2007 and 2011.