Exchange Rate Flexibility under the Zero Lower Bound: the Need for Forward Guidance

Macroeconomic theory says that when a country is vulnerable to idiosyncratic macro shocks, it should have its own currency and a flexible exchange rate. But recently in many countries, interest rates have been pushed down close to the lower bound, limiting the ability of policy-makers to accommodate shocks, even in countries with flexible exchange rates. This paper argues that if the zero bound constraint is binding and policy lacks an effective ‘forward guidance’ mechanism, a flexible exchange rate system may be inferior to a single currency area, even in face of country-specific macro shocks. With monetary policy constrained by the zero bound, under flexible exchange rates, the exchange rate exacerbates the impact of shocks. Remarkably, this may hold true even if only a subset of countries are constrained by the zero bound, and other countries freely adjust their interest rates under an optimal targeting rule. In a zero lower bound environment, in order for a regime of multiple currencies to dominate a single currency, it is necessary to have effective forward guidance in monetary policy.