A private, not-for-profit provider of financial regulatory services that owns the NASDAQ stock market as well as NASD Regulation Inc., which is an independent subsidiary that regulates brokers and dealers on the NASDAQ stock market and the over-the-counter securities market. NASD registers member firms and creates rules to govern their behavior, monitors their actions for compliance, and disciplines firms or brokers that break the rules. It also operates arbitration and mediation programs to resolve securities disputes. Federal law requires that nearly every securities firm conducting business with a U.S. public company must be a member of NASD. Members of NASD include about 5,300 brokerage firms with 91,000 branch offices and  662,000 registered securities representatives. NASD is headquartered in Washington, D.C., with offices and a market site in New York City. NASD also has district offices throughout the U.S.