というNBER論文をマイケル・ウッドフォード(Michael Woodford)が上げているungated版)。原題は「Monetary Policy Analysis when Planning Horizons are Finite」で、今年初めにアメリカ経済学会でのプレゼンの模様についてunrepresentative agentさんが紹介している

It is common to analyze the effects of alternative monetary policy commitments under the assumption of fully model-consistent expectations. This implicitly assumes unrealistic cognitive abilities on the part of economic decision makers. The relevant question, however, is not whether the assumption can be literally correct, but how much it would matter to model decision making in a more realistic way. A model is proposed, based on the architecture of artificial intelligence programs for problems such as chess or go, in which decision makers look ahead only a finite distance into the future, and use a value function learned from experience to evaluate situations that may be reached after a finite sequence of actions by themselves and others. Conditions are discussed under which the predictions of a model with finite-horizon forward planning are similar to those of a rational expectations equilibrium, and under which they are instead quite different. The model is used to re-examine the consequences that should be expected from a central-bank commitment to maintain a fixed nominal interest rate for a substantial period of time. “Neo-Fisherian” predictions are shown to depend on using rational expectations equilibrium analysis under circumstances in which it should be expected to be unreliable.


Similar conclusions about the instability of learning dynamics under an interest-rate peg have been obtained in the context of New Keynesian models based on intertemporal optimization by authors including Bullard and Mitra (2002), Preston (2005), and Evans and McGough (2017). The present model illustrates, however, that such conclusions can be obtained without modeling expectations as purely backward-looking, as these authors do. The present analysis does allow central-bank announcements about intended future policy to influence behavior immediately, even before any change in actual central-bank behavior occurs, because it is assumed that households and firms should both take into account such information in their forward planning exercises. But this does not imply dynamics that converge to a stationary equilibrium consistent with the Fisher equation.


*2:cf. これ

*3:cf. ここ