Has the U.S. Federal Reserve's tone regarding its stance toward its asset purchase program(quantitative easing part 2, or QE2), changed?

From the recent comments of Federal Open Market Committee members, it's tough to detect a shift.

For investors, the Fed's QE2 tone is hardly insignificant. A Fed signal that an unwinding of asset purchases is likely before June would affect U.S GDP growth expectations, and, by extension, corporate revenue expectations of many firms for the second half of 2011.

In what could be determined as the understatement of the day, Federal Reserve Bank of Philadelphia President Charles Plosser told a group assembled at a banking forum in Prague that monetary policymakers must be vigilant to ensure rules-based policy decisions aren't skewed by poor data.

Plosser listed problems that are associated with measuring output gaps. An output gap is defined as the difference between the actual output of an economy and the output it could achieve at its most efficient. An output gap can be positive or negative (positive means actual output is more than full-capacity output and vice versa for negative). Plosser believes that output gaps and/or unemployment gaps could appear bigger than they are, which could lead to incorrect decisions as it comes to inflation. Plosser believes that "Explaining such decisions about the appropriate stance of monetary policy will be challenging, and central bankers will need to communicate with the public about these issues well in advance of their decisions to ensure that their policy actions are not misunderstood."

Federal Reserve Bank of Philadelphia President Charles Plosser indicated that further interest rate reductions may be needed to stimulate the U.S. economy, should economic growth become "substantially weaker" than already projected, Bloomberg News reported Tuesday.

"A substantially weaker outlook than expected, particularly if that weakness is projected to be more prolonged than anticipated, may require further adjustments to policy,'' Plosser said in a speech in Gladwyne, Pennsylvania, adding that he already expects several ``sluggish'' quarters of growth, Bloomberg News reported.

However, Plosser also told Reuters that he's "concerned that developments on the inflation front will make the Fed's policy decisions more difficult in 2008."

The Fed's preferred measure of consumer prices has risen 2.2% on a November 2006-November 2007 basis, or at a rate above the Fed's comfort zone, leading many economists to argue that the Fed may not be as stimulative as it typically would be at this stage of the economic cycle. The Fed may also continue to use non-interest rate policy options to encourage economic activity, these economists say.