I received the following question from one of my list members today:
"... you referred to the currency exchange cash market and the fact that this is basically a market between banks across countries. Does this mean that, for example, the EURO/USD exchange rate is set between the Federal Reserve and the ECB? Is that how a price is established without the benefit of any trading on any listed exchange anywhere else? Thanks for the brief education on this particular point." - Stan Z.
The forex spot market is primarily an "interbank" market. That means the majority of the trading volume is done bank-to-bank such as between Citibank and Goldman Sachs, for example. This trading is generally done on behalf of banking customers such as multinational corporations, though the banks also trade with each other both to hedge their currency exposure and to take on trading positions.
This sort of market structure is the same as the one for most cash market government debt trading, such as that for US Treasury Bonds and the like. You can think of it like the over-the-counter market for stocks. Those trades don't go through an exchange, but are done directly broker-to-broker.
In both forex and fixed income there are big players like hedge funds that take part along with the commercial and investment banks. The world's central banks are also major participants at this level in their attempts to influence exchange rates (forex) and/or interest rates (fixed income).
The transaction sizes in the interbank market are large - generally $5 million and up. Obviously, the average individual trader is not going to be trading anywhere near that big. That's where the online brokers and forex dealers come in to play. They allow small traders to do transactions in significantly lower amounts. In fact, there is at least one which will do trades as small as $1.
Here is where some folks get a bit nervous. Many of these forex dealers actually act as market makers with their clientele. By that I mean they take the other side of the trades that are done by their customers. This is something which can sometimes happen in the stock market as well, especially with OTC stocks. The concern that folks have with this is the implied conflict of interest in terms of price execution that creates. Is a dealer who will be taking the other side of your trade going to be acting in your best interest when you put on a trade?
While it may be true that some unscrupulous dealers may take advantage of their customers in that way, I am quite confident that most of them are not acting against their customers. They simply provide liquidity to the market and earn the spread to do so. When they have an excessive exposure to any particular currency, they offset it by hedging in the interbank market or with another dealer. That's basically the same as a floor trader on any exchange.
Getting to the question of how prices get set, the market does that, not the central banks. Each individual bank and dealer is actually setting its own price. That might sound a bit strange in that it would create different rates all over the place. The fact of the matter is, however, that prices between dealers and banks are almost always going to be very, very close. There are services such as Reuters where dealer prices are aggregated and presented in data feeds, allowing everyone to know the current (and historical) market rates. Arbitrage trading keeps dealers from quoting prices too far away from each other.
There is also trading in the futures market, and the relatively new currency exchange traded funds (ETFs). The activity there, while only a small fraction of the global market volume, also contributes to keeping prices in line across the board.