(Updated with latest ADP private-sector employment numbers)NEW YORK ( TheStreet) -- Will the Federal Reserve's move to boost the flagging U.S. economy be too little to make a difference or will it be too much, too soon? That is the big question for investors anxiously awaiting the Federal Open Market Committee statement on Wednesday afternoon. The S&P 500 has risen 14% since the central bank first hinted that it will resume the purchase of long-term assets to boost the economy -- dubbed QE2 -- in August. While the prospect of quantitative easing has driven down the dollar and helped push up stocks, investors remain uncertain of what the actual outcome of the Fed's move will be on the economy and job growth, as the central bank heads into unchartered territory. Skeptics have said that further quantitative easing will do little to help an economy that is stuck in a "liquidity trap" and would only succeed in creating dangerous asset inflation. Supporters argue that the Fed must use every tool it has at its disposal to prevent the economy from slipping back into a recession and to keep the threat of deflation at bay. Fed chairman Ben Bernanke and his colleagues have, in various speeches over the last two months, tried to steer market expectations in a spirit of transparency. But
Bethune of Global Insight does not think a front-ending of the purchases is likely, however. "There is not enough supply to be front-ended. The Fed does not want to disrupt the treasury auction market too much," he said. Bethune expects the policy statement to contain language that suggests the program will be adjusted based on how the economy progresses. Bernanke already said in his Oct. 16 speech that the Fed will have to proceed with caution given central banks' relative inexperience with this move. "One disadvantage of asset purchases relative to conventional monetary policy is that we have much less experience in judging the economic effects of this policy instrument, which makes it challenging to determine the appropriate quantity and pace of purchases and to communicate this policy response to the public," Bernanke noted. "These factors have dictated that the Federal Open Market Committee proceed with some caution in deciding whether to engage in further purchases of longer-term securities."