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The foreign exchange (currency or forex or FX) market exists wherever one currency is traded for another. It is by far the largest market in the world, in terms of cash value traded, and includes trading between large banks, central banks, currency speculators, multinational corporations, governments, and other financial markets and institutions. The trade happening in the forex markets across the globe currently exceeds $1.9 trillion/day (on average). Retail traders (individuals) are currently a very small part of this market and may only participate indirectly through brokers or banks and may be targets of forex scams.

According to David Krutz from the Financial Times website (Published: October 9 2006 20:48) " The foreign exchange market will have doubled in size in just three years next year, thanks to increased participation by fund managers and pension funds, says research out on Monday. TowerGroup, a financial services research consultancy, said it expected total global average daily volumes on the FX market to exceed $3,000bn in 2007. FX volumes, which rose from $1,770bn in 2004 to $2,000bn last year, were set to rise to $2,600bn this year and $3,600bn next year, as foreign exchange became accepted as an asset class in its own right according to TowerGroup.

Wikipedia.org