A big demand slump isn’t just an economic disaster; it’s also a prediction of an economic disaster. And that means it’s a prediction of policy failure. At least that’s the implication of the Woodfordian view of macro (which I accept.) Changes in current AD are mostly driven by changes in the future path of AD. Changes in near-term NGDP are mostly driven by changes in expected NGDP 1, 2, 5 and 10 years out in the future. Call it the term structure of NGDP. And those are driven by the future expected path of monetary policy.