Optimal Forward Guidance
研究了在流动性陷阱结束后保持低利率的最优时长，给出了闭式解，并发现简单规则“宣布持续时间为陷阱持续时间的一半乘以冲击”是良好近似，且优于奥德赛式承诺。
Optimal forward guidance is the simple policy of keeping interest rates low for some optimally determined number of periods after the liquidity trap ends and moving to normal-times optimal policy thereafter. I solve for the optimal duration in closed form in a new Keynesian model and show that it is close to fully optimal Ramsey policy. The simple rule “announce a duration of half of the trap’s duration times the disruption” is a good approximation, including in a medium-scale dynamic stochastic general equilibrium (DSGE) model. By anchoring expectations of Delphic agents (who mistake commitment for bad news), the simple rule is also often welfare-preferable to Odyssean commitment.