How will we gauge how much to do? This is a difficult question without a ready answer, even under more normal circumstances when we are focused on the federal funds rate, and it is an even harder judgment when, as now, the federal funds rate is near zero and we are intervening in other ways to affect financial conditions.
We have some, albeit limited, ability to gauge the effects of large-scale asset purchases on interest rates; the effects of liquidity facilities, like the Term AssetBacked Securities Loan Facility and other programs, are even more difficult to assess and predict.