Martin Wolf says its time to unload both barrels of the gun and resort to true helicopter drop-types stimulus. He has the right idea, but it could be better implemented through an explicit price level or nominal GDP level target. Doing so is important because as Josh Hendrickson notes no one at the Fed or the ECB knows exactly how much to print. What the central banks can do, though, is properly shape expectations about future nominal spending and price growth. Doing so would cause the markets themselves to do much of the heavy lifting (through expectation-induced portfolio rebalancings) and in the process ensure the Fed's goals are realized. Josh Hendrickson sums it up this point nicely:
Update: Here I go into more detail as to how the Fed would work to shape expectations through a nominal GDP level target.The Federal Reserve’s focus on the size of its asset purchases represents a grave mistake. There is no model that tells us the precise size increase in the central bank balance sheet will get us to a desired level of nominal income. Those who continue to claim that the magnitude of monetary and fiscal policy haven’t been large enough fail to recognize this point. This is the lesson of the Lucas Critique. Expectations matter.