An index in which the price is determined by the price of individual stocks, weighted for total market value. For example, if the price of a component stock of the index changes, its effect on the index as a whole is proportionate to share's price multiplied by the number of shares the company has outstanding. This means that changes in price will affect the index more if the component company has greater value. Most non-American market value-weighted indices give further weighting (called float-weighted indexing) to properly account for partial government ownership of many large corporations. This method of index weighting contrasts with a price-weighted index, in which all price changes are weighted differently, and a market share-weighted index, which weights only by the number of shares outstanding and not by their value. Major examples of a market value-weighted index include the NASDAQ Composite Index and the Standard & Poor's 500. The latter uses float-weighted indexing to match its calculations more closely with foreign counterparts.
A measure of security prices adjusted according to the market value of each security included in the average. The greater a firm's number of shares outstanding and the higher the price of the shares, the greater the weight of that security in a market-value-weighted average. The S&P 500 is a market-value-weighted average. Compare price-weighted average.