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If the Dow is the establishment, the National Association of Securities Dealer Automated Quotations (NASDAQ) National Market System Composite Index is the workhorse of market indices. This index monitors common stock that is traded on the NASDAQ system (also known as over-the-counter stocks).
Plain English
The NASDAQ National Market System Composite Index is an index composed of over-the-counter stock that is being traded on the NASDAQ system. Owing to the type of stocks inherent in this market, it is considered to best represent younger, more mobile companies.