An index that includes all NASDAQ domestic and foreign common stocks. It is the most commonly cited index when referring to the performance of the NASDAQ stock market. The composite index is market-value weighted so that each companyÂ’s stock price affects the index in proportion to its market value. During the technology boom of the late 1990s, the NASDAQ composite often was cited as technology heavy. However, since the technology boom ended and many of the start-up dot-com companies have failed, that description is rarely used. Securities on the NASDAQ composite index typically are assigned to subindices.