In locally linearized dynamic stochastic rational‐expectations models, I introduce the concepts of feasible paths (paths on which the policy instrument can be expressed as a function of the policymaker's observation set) and implementable paths (paths that can be obtained, in a minimally robust way, as the unique local equilibrium under a policy‐instrument rule consistent with the policymaker's observation set). I show that, for relevant observation sets, the optimal feasible path under monetary policy can be non‐implementable in the new Keynesian model, while constant‐debt feasible paths under tax policy are always implementable in the real business cycle model. The first result sounds a note of caution about one of the main lessons of the new Keynesian literature, namely the importance for central banks to track some key unobserved exogenous rates of interest, while the second result restores to some extent the role of income or labor‐income taxes in safely stabilizing public debt. For any given implementable path, I show how to design arithmetically a policy‐instrument rule consistent with the policymaker's observation set and implementing this path as the robustly unique local equilibrium.

中文翻译：

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实施稳定政策

在局部线性化的动态随机理性预期模型中，我介绍了可行路径（政策工具可以表示为政策制定者观察集的函数的路径）和可实现路径（可以在最小稳健性中获得的路径）的概念。方式，作为与政策制定者的观察集一致的政策工具规则下的唯一局部均衡）。我表明，对于相关的观察集，货币政策下的最优可行路径在新凯恩斯模型中是不可实现的，而税收政策下的恒定债务可行路径在真实的商业周期模型中总是可以实现的。第一个结果听起来是对新凯恩斯主义文学的主要教训之一的警告，即中央银行跟踪一些关键的未观察到的外生利率的重要性，而第二个结果在一定程度上恢复了所得税或劳动所得税在安全稳定公共债务方面的作用。对于任何给定的可实现路径，我将展示如何在算术上设计与决策者的观察集一致的策略工具规则，并将该路径实现为稳健唯一的局部均衡。