The Ramsey approach to policy analysis finds the best competitive equilibrium given a set of available instruments. This approach is silent about unique implementation, namely designing policies so that the associated competitive equilibrium is unique. This silence is particularly problematic in monetary policy environments where many ways of specifying policy lead to indeterminacy. We show that sophisticated policies which depend on the history of private actions and which can differ on and off the equilibrium path can uniquely implement any desired competitive equilibrium. A large literature has argued that monetary policy should adhere to the Taylor principle to eliminate indeterminacy. Our findings say that adherence to the Taylor principle on these grounds is unnecessary. Finally, we show that sophisticated policies are robust to imperfect information.
Monetary policy ; Taylor's rule
In standard approaches to monetary policy, interest rate rules often lead to indeterminacy. Sophisticated policies, which depend on the history of private actions and can differ on and off the equilibrium path, can eliminate indeterminacy and uniquely implement any desired competitive equilibrium. Two types of sophisticated policies illustrate our approach. Both use interest rates as the policy instrument along the equilibrium path. But when agents deviate from that path, the regime switches, in one example to money; in the other, to a hybrid rule. Both lead to unique implementation, while pure interest rate rules do not. We argue that adherence to the Taylor principle is neither necessary nor sufficient for unique implementation with pure interest rate rules but is sufficient with hybrid rules. Our results are robust to imperfect information and may provide a rationale for empirical work on monetary policy rules and determinacy.
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