A theory that states that, in the long-run, a central bank that hopes to conduct independent monetary policy must choose between maintaining a fixed foreign exchange rate and allowing the free movement of capital. For instance, a central bank that chooses to increase the total money supply by adopting loose monetary policy cannot hope to maintain the foreign exchange value of its currency unless it resorts to restricting the sale of domestic currency in the currency market. The idea is derived from the academic works of Canadian economist Robert Mundell and British economist Marcus Fleming.
