But many believe that assuming the taper is $10-$15 billion, it is built into the market. No tapering would move the markets to the upside, and a $20 billion taper would likely send markets reeling. Given this, the size of the taper may not be the main driver for the markets, particularly for interest rates.
What would move rates? Several things...the Fed could:
1) change its forward guidance; they could, for example, lower the unemployment rate threshold for the first Fed funds hike from 6.5 percent to, say 6 percent;
2) change the way they have been communicating the end of the tapering process, from mid-2014 to some other date, and;
3) indicate that the current level of purchases may be adequate for a longer period, which would remove expectations for more tapering during its next meeting, on October 29-30.
Another market-moving event could be the 2016 forecasts, which will be introduced today. That will also be used to emphasize the message that actual increases in the Fed funds rate, once it begins, will be very gradual, thus emphasizing that "tapering is not tightening."
Bernanke has to convince the bond market the first rate hike is mid-2015, and must hint at the pace of the taper.
—By CNBC's Bob Pisani