Computerized subscriber service that serves as a vehicle for the fourth market. "Instinet" is registered with the SEC As a stock exchange it numbers among its subscribers a large number of mutual funds and other institutional investors linked to each other by computer terminals. The system permits subscribers to display bids and offers (which are exposed system wide for whatever length of time the initiating party specifies) and to consummate trades electronically. Instinet is largely used by market makers, but, nonmarket makers and customers have equal access.