Although Fed Chairman Ben Banke did not announce another round of quantitative easing (QE)during his speech at the annual Jackson Hole,Wyoming,retreat for central bankers,he did leave the door open tor turlthcr stimulus.Given the dismal state of the U.S.economy after QE2,which pumped nearly $600 billion into longer-term Treasury securities designed to lower interest rates and encourage investment,Bcmanke should be humble in his expectations about what the Fed can do to generate economic growth.