A Note on Imperfect Credibility

Abstract

We explore how outcomes of optimal monetary policy with loose commitment (Schaumburg and Tambalotti, 2007; Debortoli and Nunes, 2010) can be observationally equivalent, or interpretable as outcomes of deeper optimal policy under sustainable plans (Chari and Kehoe, 1990). Both interpretations of “imperfect credibility” in optimal monetary policy design are attempts to rationalize outcomes that lie in between the conventional extremes of optimal policy under commitment and under discretion. In a standard monetary-policy framework, when we match impulse responses of inflation and the output gap to large enough markup shocks, we find that a small probability (1 – a = 0.05) of replanning in the quasi/loose commitment world corresponds to N = 18 in the N-period punishment optimal sustainable monetary policy, in terms of observable outcomes. For plausible cases of loose-commitment model economies (with a between 0.77 and 1) we can find an observationally equivalent sustainable-plan economy indexed by some N.

Keywords: imperfect credibility, monetary policy, sustainable policy

JEL Classification: E52, E58, E61