Existence and Uniqueness of Solutions to Dynamic Models with Occasionally Binding Constraints
研究了零利率下限等偶尔约束导致多重均衡的问题，给出了线性模型存在唯一确定性解的条件，并发现价格水平目标可恢复唯一性。
Abstract Occasionally binding constraints (OBCs) like the zero lower bound (ZLB) can lead to multiple equilibria, and so to belief-driven recessions. To aid in finding policies that avoid this, we derive existence and uniqueness conditions for otherwise linear models with OBCs. Our main result gives necessary and sufficient conditions for such models to have a unique (“determinate”) perfect foresight solution returning to a given steady state, for any initial condition. While standard New Keynesian models have multiple perfect-foresight paths eventually escaping the ZLB, price level targeting restores uniqueness. We also derive equilibrium existence conditions under rational expectations for arbitrary nonlinear models.