Many other industrialized nations also switched from a system of fixed exchange rates to a system of floating rates. Since 1973, exchange rates for most industrialized countries have floated, or fluctuated, according to the supply of and demand for different currencies in international markets. An increase in the value of a currency is known as appreciation, and a decrease as depreciation. Some countries and some groups of countries, however, continue to use fixed exchange rates to help to achieve economic goals, such as price stability. Under a fixed exchange rate system, only a decision by a country's government or monetary authority can alter the official value of the currency.
Governments do, occasionally, take such measures, often in response to unusual market pressures.
For example, suppose a government has set 10 units of its currency equal to one dollar. To devalue, it might announce that from now on 20 of its currency units will be equal to one dollar. This would make its currency half as expensive to Americans, and the U.S. dollar twice as expensive in the devaluing country. When a government devalues its currency, it is often because the interaction of market forces and policy decisions has made the currency's fixed exchange rate untenable. In order to sustain a fixed exchange rate, a country must have sufficient foreign exchange reserves, often dollars, and be willing to spend them, to purchase all offers of its currency at the established exchange rate.