The World’s ‘Reserve’ Currency Mandate is the US dollar. Everything is priced and traded in US dollars. If you have pesos and want to buy a barrel of oil on the open market then you first have to convert pesos to the US dollar value at time of purchase. FOREX markets track foreign currency values against the US$.
From: http://www.answers.com/topic/foreign-exchange-market#ixzz1fRuHXVrr
On the spot market, according to the 2010 Triennial Survey, the most heavily traded bilateral currency pairs were:
EURUSD: 28%
USDJPY: 14%
GBPUSD (also called cable): 9%
and the US currency was involved in 84.9% of transactions, followed by the euro (39.1%), the yen (19.0%), and sterling (12.9%) (see table). Volume percentages for all individual currencies should add up to 200%, as each transaction involves two currencies.
Trading in the euro has grown considerably since the currency’s creation in January 1999, and how long the foreign exchange market will remain dollar-centered is open to debate. Until recently, trading the euro versus a non-European currency ZZZ would have usually involved two trades: EURUSD and USDZZZ. The exception to this is EURJPY, which is an established traded currency pair in the interbank spot market. As the dollar’s value has eroded during 2008, interest in using the euro as reference currency for prices in commodities (such as oil), as well as a larger component of foreign reserves by banks, has increased dramatically. Transactions in the currencies of commodity-producing countries, such as AUD, NZD, CAD, have also increased.
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A bit dated but notice how there is interest in using other currencies like the Euro to price commodities but you can see what a meltdown is happening there forcing everyone back to US$ commodity pricing. Probably back above 90% for commodities price in US dollars now.
If you want to be taken seriously, answers.com isn’t helping your cause.