The bid/offer spread (also known as bid/ask spread) for securities (such as stock, futures contracts, options, or currency pairs) is the difference between the price quoted by a market maker for an immediate sale (bid) and an immediate purchase (ask). The size of the bid-offer spread in a given commodity is a measure of the liquidity of the market and the size of the transaction cost.
The trader initiating the transaction is said to demand liquidity, and the other party (counterparty) to the transaction supplies liquidity. Liquidity demanders place market orders and liquidity suppliers place limit orders. For a round trip (a purchase and sale together) the liquidity demander pays the spread and the liquidity supplier earns the spread.
All limit orders outstanding at a given time (i.e., limit orders that have not been executed) are together called the Limit Order Book. In some markets such as NASDAQ, dealers supply liquidity. However, on most exchanges, such as the Australian Securities Exchange, there are no designated liquidity suppliers, and liquidity is supplied by other traders.
On these exchanges, and even on NASDAQ, institutions and individuals can supply liquidity by placing limit orders
Tuesday, June 2, 2009
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