Escape Dynamics and Policy Specification

In his monograph The conquest of American inflation (1999) Sargent suggests that the sharp reduction in US inflation that took place under Volker may vindicate the type of econometric policy evaluation famously criticized by Lucas (1976). At the core of this vindication strory are the escape dynamics, recurrent sliding away from the path leading to the time-consistent sub-optimal equilibrium level of inflation. We try to understand here under which conditions this phenomenon arises. In particular, we note that economists, and consequently policymakers, knew long before the Lucas critique that in order to do policy analysis structural models were required. We thus endow our policymaker with a correctly specified model, one that takes explicitly into account the role of expectations. Using such a model, together with a policy that takes expectations as given, the escape dynamics do not appear. But they reappear when long run considerations of policy effects enter into the picture. We thus conclude that what really matters is the way in which the policymaker designs its policy, rather than the econometric specification of the model he uses.