The document summarizes the Federal Reserve's use of quantitative easing (QE) to stimulate the US economy following the Great Recession. It describes the four QE programs undertaken by the Fed between 2008-2014 to increase the money supply and lower interest rates. While QE helped lead to recovery in the short-run through higher GDP and lowered unemployment, the document speculates the economy remains vulnerable in the long-run without further QE due to its dependence on low interest rates and money supply growth to sustain expansion.