Learn more about Currency
A currency is a unit of exchange, facilitating the transfer of goods and services. It is a form of money, where money is defined as a medium of exchange (rather than a store of value). A currency zone is a country or region in which a specific currency is the dominant medium of exchange. To facilitate trade between currency zones, there are exchange rates i.e. prices at which currencies (and the goods and services of individual currency zones) can be exchanged against each other. Currencies can be classified as either floating currencies or fixed currencies based on their exchange rate regime. In common usage, currency sometimes refers to only paper money, as in "coins and currency", but this is misleading. Coins and paper money are both forms of currency.
In most cases, each country has monopoly control over the supply and production of its own currency. Member countries of the European Monetary Union are a notable exception to this rule, as they have ceded control of monetary policy to the European Central Bank.
In cases where a country does have control of its own currency, that control is exercised either by a central bank or by a Ministry of Finance. In either case, the institution that has control of monetary policy is referred to as the monetary authority. Monetary authorities have varying degrees of autonomy from the governments that create them. In the United States, the Federal Reserve operates without direct interference from the legislature or executive. It is important to note that a monetary authority is created and supported by its sponsoring government, so independence can be reduced or revoked by the legislative or executive authority that creates it. However, in practical terms, the revocation of authority is not likely since those who have the power to do so are generally beholden to the Fed for their positions. In almost all Western countries, the monetary authority is largely independent from the government.
Several countries can use the same name, each for their own currency (e.g. Canadian dollars and US dollars), several countries can use the same currency (e.g. the euro), or a country can declare the currency of another country to be legal tender. For example, Panama and El Salvador have declared US currency to be legal tender, and from 1791-1857, Spanish silver coins were legal tender in the United States. At various times countries have either restamped foreign coins, or used currency board issuing one note of currency for each note of a foreign government held, as Ecuador currently does.
Each currency typically has one fractional currency, often valued at 1⁄100 of the main currency: 100 cents = 1 dollar, 100 centimes = 1 franc, 100 pence = 1 pound. Units of 1⁄10 or 1⁄1000 are also common, but some currencies do not have any smaller units. Mauritania and Madagascar are the only remaining countries that do not use the decimal system; instead, the Mauritanian ouguiya is divided into 5 khoum, while the Malagasy ariary is divided into 5 iraimbilanja. However, due to inflation, both fractional units have in practice fallen into disuse.
See Non-decimal currencies for other (mostly historic) currencies with non-decimal divisions.
 Early currency
The origin of currency is the creation of a circulating medium of exchange based on a unit of account which quickly becomes a store of value. Currency evolved from two basic innovations: the use of counters to assure that shipments arrived with the same goods that were shipped, and later with the use of silver ingots to represent stored value in the form of grain. Both of these developments had occurred by 2000 BC. Originally money was a form of receipting grain stored in temple granaries in Egypt and ancient Mesopotamia.
This first stage of currency, where metals were used to represent stored value, and symbols to represent commodities, formed the basis of trade in the Fertile Crescent for over 1500 years. However, the collapse of the Near Eastern trading system pointed to a flaw: in an era where there was no place that was safe to store value, the value of a circulating medium could only be as sound as the forces that defended that store. Trade could only reach as far as the credibility of that military. By the late Bronze Age, however, a series of international treaties had established safe passage for merchants around the Eastern Mediterranean, spreading from Minoan Crete and Mycenae in the North West to Elam and Bahrein in the South East. Although it is not known what functionbed as a currency to facilitate these exhanges, it is thought that ox-hide shaped ingots of copper, produced in Cyprus may have functioned as a currency.
It is thought that the increase in piracy and raiding associated with the Late Bronze Age general systems collapse, possibly produced by the Peoples of the Sea brought this trading system to an end. It was only with the recovery of Phoenician trade in the ninth and tenth centuries, that saw a return to prosperity, and the appearance of real coinage, possibly first in Anatolia with Croesus of Lydia and subsequently with the Greeks and Persians.
These factors led to the shift of the store of value being the metal itself: at first silver, then both silver and gold. Metals were mined, weighed, and stamped into coins. This was to assure the individual taking the coin that he was getting a certain known weight of precious metal. Coins could be counterfeited, but they also created a new unit of account, which helped lead to banking. Archimedes' principle was that the next link in currency occurred: coins could now be easily tested for their fine weight of metal, and thus the value of a coin could be determined, even if it had been shaved, debased or otherwise tampered with (see Numismatics).
In most major economies using coinage, copper, silver and gold formed three tiers of coins. Gold coins were used for large purchases, payment of the military and backing of state activities. Silver coins were used for large, but common, transactions, and as a unit of account for taxes, dues, contracts and fealty, while copper coins represented the coinage of common transaction. This system had been used in ancient India since the time of the Mahajanapadas. In Europe, this system worked through the medieval period because there was virtually no new gold, silver or copper introduced through mining or conquest. Thus the overall ratios of the three coinages remained roughly equivalent.
 The era of hard and credit money
In China, the need for credit and for circulating medium led to the introduction of paper money, commonly known today as banknotes. In Europe paper money was first introduced in Sweden 1661. Sweden was rich on copper, thus, because of copper's low value, extraordinarily big coins (often weighing several kilograms) had to be made. Because the coin was so big, it was probably more convenient to carry a note stating your possession of such a coin than to actually carry the coin itself.
Paper money was, in one sense, a return to the oldest form of currency: it represented a store of value backed by the credibility of the issuing authority. Drafts and checks issued privately had been in intermittent use for centuries, however, it was with the rise of global trade that paper money would find a permanent place in currency.
The advantages of paper currency were numerous: it reduced transport of gold and silver, and thus lowered the risks; it made loaning gold or silver at interest easier, since the specie (gold or silver) never left the possession of the lender until someone else redeemed the note; and it allowed for a division of currency into credit and specie backed forms. It enabled the sale of stock in joint stock companies, and the redemption of those shares in paper.
However, these advantages held within them disadvantages. First, since a note has no intrinsic value, there was nothing to stop issuing authorities from printing more of it than they had specie to back it with. Second, because it created money that did not exist, it increased inflationary pressures, a fact observed by David Hume in the 18th century. The result is that paper money would often lead to an inflationary bubble, which could collapse if people began demanding hard money, causing the demand for paper notes to fall to zero. The printing of paper money was also associated with wars, and financing of wars, and therefore regarded as part of maintaining a standing army.
For these reasons, paper currency was held in suspicion and hostility in Europe and America. It was also addictive, since the speculative profits of trade and capital creation were quite large. Major nations established mints to print money and mint coins, and branches of their treasury to collect taxes and hold gold and silver stock.
 Legal tender era
With the creation of central banks, currency underwent several significant changes. During both the coinage and credit money eras the number of entities which had the ability to coin or print money was quite large. One could, literally, have "a license to print money"; many nobles had the right of coinage. Royal colonial companies, such as the Massachusetts Bay Company or the British East India Company could issue notes of credit—money backed by the promise to pay later, or exchangeable for payments owed to the company itself. This led to continual instability of the value of money. The exposure of coins to debasement and shaving, however, presented the same problem in another form: with each pair of hands a coin passed through, its value grew less.
The solution which evolved beginning in the late 18th century and through the 19th century was the creation of a central monetary authority which had a virtual monopoly on issuing currency, and whose notes had to be accepted for "all debts public and private". The creation of a truly national currency, backed by the government's store of precious metals, and enforced by their military and governmental control over an area was, in its time, extremely controversial. Advocates of the old system of Free Banking repealed central banking laws, or slowed down the adoption of restrictions on local currency. (See Gold standard for a fuller discussion of the creation of a standard gold based currency).
At this time both silver and gold were considered legal tender, and accepted by governments for taxes. However, the instability in the ratio between the two grew over the course of the 19th century, with the increase both in supply of these metals, particularly silver, and of trade. This is called bimetallism and the attempt to create a bimetallic standard where both gold and silver backed currency remained in circulation occupied the efforts of inflationists. Governments at this point could use currency as an instrument of policy, printing paper currency such as the United States Greenback, to pay for military expenditures. They could also set the terms at which they would redeem notes for specie, by limiting the amount of purchase, or the minimum amount that could be redeemed.
By 1900, most of the industrializing nations were on some form of gold standard, with paper notes and silver coins constituting the circulating medium. Governments too followed Gresham's Law: keeping gold and silver paid, but paying out in notes.
 The paper money era
A banknote (more commonly known as a bill in the United States and Canada) is a type of currency, and commonly used as legal tender in many jurisdictions. With coins, banknotes make up the cash form of all modern money.
 Modern currencies
To find out which currency is used in a particular country, check list of circulating currencies.
Nowadays, the International Organization for Standardization has introduced a system a three-letter system of codes (ISO 4217) to define currency (as opposed to simple names or currency signs), in order to remove the confusion that there are dozens of currencies called the dollar and many called the franc. Even the pound is used in nearly a dozen different countries, all, of course, with wildly differing values. In general, the three-letter code uses the ISO 3166-1 country code for the first two letters and the first letter of the name of the currency (D for dollar, for instance) as the third letter.
The International Monetary Fund uses a variant system when referring to national currencies.
 Privately issued currencies
- See also: Private currency
From the earliest times token coins were issued by companies in remote parts of the world to overcome the shortage of circulating currency.
Several large companies issue points to their customers, to be redeemed for products and services produced by that company. Often, a network of companies will join to share in the offering and redemption of points. While these can hardly be considered stable currency systems, they present many of the same features as "legitimate" currency: they are a store of value, issued in discrete units; they are controlled by a central issuing authority; and they have varying rates of exchange with other forms of currency. For example, frequent flyer miles can be bought using U.S. dollars.
- Alternative currency: A currency such as the Liberty Dollar, with a one-to-one exchange rate with the U.S. Dollar.
- Frequent flyer miles: A type of private currency, different versions of which are issued by most major airlines to encourage customer loyalty. Other customer loyalty incentives have followed this model, including points systems offered by soft drink manufacturers such as PepsiCo. Subway tokens, issued by city transit authorities, can be considered a highly specialized form of currency.
- Scrip: A type of private currency where a certain value is captured, and used to purchase goods from a company. Examples of scrip include gift certificates, gift cards, and Disney Dollars, Canadian Tire Money and more recently Microsoft Points on the Xbox Live Marketplace. However, scrip is not considered a currency in itself, but merely a store of value, denominated in another currency.
 Local currencies
- See also: Local currency
In economics, a local currency is a currency not backed by a national government, and intended to trade only in a small area. Advocates such as Jane Jacobs argue that this enables an economically depressed region to pull itself up, by giving the people living there a medium of exchange that they can use to exchange services and locally-produced goods (In a broader sense, this is the original purpose of all money.) Opponents of this concept argue that local currency creates a barrier which can interfere with economies of scale and comparative advantage, and that in some cases they can serve as a means of tax evasion.
Local currencies can also come into being when there is economic turmoil involving the national currency. An example of this is the Argentine economic crisis of 2002 in which IOUs issued by local governments quickly took on some of the characteristics of local currencies.
 Single global currency
With such developments as the euro allowing for facilitated trade and perhaps a corresponding increase in a wider identity, proposals for a single global currency have accelerated, even while it is recognized that several political and economic factors would need to be addressed and intermediate steps taken before such a concept might be accepted by the diverse nations of the world.
 Lists of currencies
- List of currencies
- List of circulating currencies
- List of historical currencies
- Fictional currencies
 Accounting units
- Franc Poincaré
- Special Drawing Rights
- European Currency Unit
- Currency sign
- Fictional currency
- Local currencies
- Currency Pair
 Proposed currencies
- Eco - West African Monetary Zone (Gambia, Ghana, Guinea, Nigeria, Sierra Leone, possibly Liberia)
- Metica - Mozambique (never implemented)
- Perun - Montenegro (never implemented)
- Amero - American currency union (hypothetical)
- East African shilling - East African Community (Burundi, Kenya, Rwanda, Tanzania, Uganda)
- Khaleeji - Gulf Cooperation Council (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates)
- Currency for Caribbean area<ref>CARICOM Single Market (CSM) ratified. This article mentions a single currency but does not speculate on a name</ref>- CARICOM states except the Bahamas
 See also</div>
- ISO 4217 Currency codes
- Non-decimal currencies
- exchange rate
- Foreign exchange
- Optimum currency area
- History of moneyar:عملة
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