| Rank | Currency | ISO 4217 code (Symbol) | % daily share (April 2007) |
|---|---|---|---|
| 1 |  United States dollar | USD ($) | 86.3% |
| 2 |  Euro | EUR (€) | 37.0% |
| 3 |  Japanese yen | JPY (¥) | 17.0% |
| 4 |  Pound sterling | GBP (£) | 15.0% |
| 5 |  Swiss franc | CHF (Fr) | 6.8% |
| 6 |  Australian dollar | AUD ($) | 6.7% |
| 7 |  Canadian dollar | CAD ($) | 4.2% |
| 8-9 |  Swedish krona | SEK (kr) | 2.8% |
| 8-9 |  Hong Kong dollar | HKD ($) | 2.8% |
| 10 |  Norwegian krone | NOK (kr) | 2.2% |
| 11 |  New Zealand dollar | NZD ($) | 1.9% |
| 12 |  Mexican peso | MXN ($) | 1.3% |
| 13 |  Singapore dollar | SGD ($) | 1.2% |
| 14 |  South Korean won | KRW (₩) | 1.1% |
| Other | 14.5% | ||
| Total | 200% | ||
There is no unified or centrally cleared market for the majority of FX trades, and there is very little cross-border regulation. Due to the over-the-counter (OTC) nature of currency markets, there are rather a number of interconnected marketplaces, where different currencies instruments are traded. This implies that there is not a single exchange rate but rather a number of different rates (prices), depending on what bank or market maker is trading, and where it is. In practice the rates are often very close, otherwise they could be exploited by arbitrageurs instantaneously. Due to London's dominance in the market, a particular currency's quoted price is usually the London market price. A joint venture of the Chicago Mercantile Exchange and Reuters, called Fxmarketspace opened in 2007 and aspired but failed to the role of a central market clearing mechanism.[citation needed]
The main trading center is London, but New York, Tokyo, Hong Kong and Singapore are all important centers as well. Banks throughout the world participate. Currency trading happens continuously throughout the day; as the Asian trading session ends, the European session begins, followed by the North American session and then back to the Asian session, excluding weekends.
Fluctuations in exchange rates are usually caused by actual monetary flows as well as by expectations of changes in monetary flows caused by changes in gross domestic product (GDP) growth, inflation (purchasing power parity theory), interest rates (interest rate parity, Domestic Fisher effect, International Fisher effect), budget and trade deficits or surpluses, large cross-border M&A deals and other macroeconomic conditions. Major news is released publicly, often on scheduled dates, so many people have access to the same news at the same time. However, the large banks have an important advantage; they can see their customers' order flow.
Currencies are traded against one another. Each currency pair thus constitutes an individual trading product and is traditionally noted XXXYYY or XXX/YYY, where XXX and YYY are the ISO 4217 international three-letter code of the currencies involved. The first currency (XXX) is the base currency that is quoted relative to the second currency (YYY), called the counter currency (or quote currency). For instance, the quotation EURUSD (EUR/USD) 1.5465 is the price of the euro expressed in US dollars, meaning 1 euro = 1.5465 dollars. Historically, the base currency was the stronger currency at the creation of the pair. However, when the euro was created, the European Central Bank mandated that it always be the base currency in any pairing.
The factors affecting XXX will affect both XXXYYY and XXXZZZ. This causes positive currency correlation between XXXYYY and XXXZZZ.
On the spot market, according to the BIS study, the most heavily traded products were:
- EURUSD: 27%
- USDJPY: 13%
- GBPUSD (also called cable): 12%
and the US currency was involved in 86.3% of transactions, followed by the euro (37.0%), the yen (17.0%), and sterling (15.0%) (see table). Volume percentages for all individual currencies should add up to 200%, as each transaction involves two currencies.
Trading in the euro has grown considerably since the currency's creation in January 1999, and how long the foreign exchange market will remain dollar-centered is open to debate. Until recently, trading the euro versus a non-European currency ZZZ would have usually involved two trades: EURUSD and USDZZZ. The exception to this is EURJPY, which is an established traded currency pair in the interbank spot market. As the dollar's value has eroded during 2008, interest in using the euro as reference currency for prices in commodities (such as oil), as well as a larger component of foreign reserves by banks, has increased dramatically. Transactions in the currencies of commodity-producing countries, such as AUD, NZD, CAD, have also increased.