forex

Foreign exchange reserves (also called Forex reserves) in a strict sense are only the foreign currency deposits held by central banks and monetary authorities. However, the term in popular usage commonly includes foreign exchange and gold, SDRs and IMF reserve positions. This broader figure is more readily available, but it is more accurately termed official reserves or international reserves. These are assets of the central bank held in different reserve currencies, such as the dollar, euro and yen, and used to back its liabilities, e.g. the local currency issued, and the various bank reserves deposited with the central bank, by the government or financial institutions.

Changes in reserves

The quantity of foreign exchange reserves can change as a central bank implements monetary policy. A central bank that implements a fixed exchange rate policy may face a situation where supply and demand would tend to push the value of the currency lower or higher (an increase in demand for the currency would tend to push its value higher, and a decrease lower). In a fixed exchange rate regime, these operations occur automatically, with the central bank clearing any excess demand or supply by purchasing or selling the foreign currency. Mixed exchange rate regimes ('dirty floats', target bands or similar variations) may require the use of foreign exchange operations (sterilized or unsterilized^[clarify]) to maintain the targeted exchange rate within the prescribed limits.

Foreign exchange operations that are unsterilized will cause an expansion or contraction in the amount of domestic currency in circulation, and hence directly affect monetary policy and inflation: An exchange rate target cannot be independent of an inflation target. Countries that do not target a specific exchange rate are said to have a floating exchange rate, and allow the market to set the exchange rate; for countries with floating exchange rates, other instruments of monetary policy are generally preferred and they may limit the type and amount of foreign exchange interventions. Even those central banks that strictly limit foreign exchange interventions, however, often recognize that currency markets can be volatile and may intervene to counter disruptive short-term movements.

To maintain the same exchange rate if there is increased demand, the central bank can issue more of the domestic currency and purchase the foreign currency, which will increase the sum of foreign reserves. In this case, the currency's value is being held down; since (if there is no sterilization) the domestic money supply is increasing (money is being 'printed'), this may provoke domestic inflation (the value of the domestic currency falls relative to the value of goods and services).

Since the amount of foreign reserves available to defend a weak currency (a currency in low demand) is limited, a foreign exchange crisis or devaluation could be the end result. For a currency in very high and rising demand, foreign exchange reserves can theoretically be continuously accumulated, although eventually the increased domestic money supply will result in inflation and reduce the demand for the domestic currency (as its value relative to goods and services falls). In practice, some central banks, through open market operations aimed at preventing their currency from appreciating, can at the same time build substantial reserves.

In practice, few central banks or currency regimes operate on such a simplistic level, and numerous other factors (domestic demand, production and productivity, imports and exports, relative prices of goods and services, etc) will affect the eventual outcome. As certain impacts (such as inflation) can take many months or even years to become evident, changes in foreign reserves and currency values in the short term may be quite large as different markets react to imperfect data.

Costs and benefits

Large reserves enhance a government's ability to amanipulate exchange rates -- but they carry an opportunity cost. The "quasi-fiscal costs" of holding reserves are the gap between the low-yield assets that asset managers typically hold, and the average cost of government debt in the country. In addition, governments can suffer losses from management of reserves - all of which is ultimately fiscal. Even in absence of a currency crisis, there can be a fiscal cost. China, for example, holds huge U.S. dollar-denominated assets, but the greenback has been weakening