Vanishing central bank intervention in stochastic impulse control.

Stochastic control of exchange rates when a central bank employs anti-inflationary stochastic differential equation (SDE) monetary policy is the key topic of our paper. Despite low money growth SDE policy means exchange rates invariably violate the central bank's targets. Monetary policy also incorporates interventions reflected by sudden money supply jumps that moderate deviations from targets. Controlling exchange rates involves minimizing target deviation and intervention costs. Restrictions on these costs ensure intervention vanishes under the optimal control, implying the central bank engineers freely floating exchange rates instead of managed floating or fixed exchange rates. Econometric evidence suggests discretionary interventions may be ineffective or generate excess volatility and speculation in currency markets. Our result demonstrates mathematically that such collateral damage discourages intervention. [ABSTRACT FROM AUTHOR]