Market size and liquidity

The foreign exchange market is unique because of
its trading volumes,
the extreme liquidity of the market,
the large number of, and variety of, traders in the market,
its geographical dispersion,
its long trading hours: 24 hours a day except on weekends (from 3pm EST on Sunday until 4pm EST Friday),
the variety of factors that affect exchange rates.
the low margins of profit compared with other markets of fixed income (but profits can be high due to very large trading volumes)
the use of leverage
As such, it has been referred to as the market closest to the ideal perfect competition, notwithstanding market manipulation by central banks. According to the BIS,[1] average daily turnover in global foreign exchange markets is estimated at $3.98 trillion. Trading in the world's main financial markets accounted for $3.21 trillion of this.
This $3.21 trillion in main foreign exchange market turnover was broken down as follows:
$1.005 trillion in spot transactions
$362 billion in outright forwards
$1.714 trillion in forex swaps
$129 billion estimated gaps in reporting
Of the $3.98 trillion daily global turnover, trading in London accounted for around $1.36 trillion, or 34.1% of the total, making London by far the global center for foreign exchange. In second and third places respectively, trading in New York accounted for 16.6%, and Tokyo accounted for 6.0%.
In addition to "traditional" turnover, $2.1 trillion was traded in derivatives.