<P> The S&P 500 stock market index , maintained by S&P Dow Jones Indices , comprises 505 common stocks issued by 500 large - cap companies and traded on American stock exchanges , and covers about 80 percent of the American equity market by capitalization . The index is weighted by free - float market capitalization , so more valuable companies account for relatively more of the index . The index constituents and the constituent weights are updated and checked on regularly using rules published by S&P Dow Jones Indices . Although the index is called the S&P `` 500 '' , the index contains 505 stocks because it includes two share classes of stock from 5 of its component companies . </P>
<P> The S&P 500 stock market index , maintained by S&P Dow Jones Indices , comprises 505 common stocks issued by 500 large - cap companies and traded on American stock exchanges , and covers about 80 percent of the American equity market by capitalization . The index is weighted by free - float market capitalization , so more valuable companies account for relatively more of the index . The index constituents and the constituent weights are updated and checked on regularly using rules published by S&P Dow Jones Indices . Although the index is called the S&P `` 500 '' , the index contains 505 stocks because it includes two share classes of stock from 5 of its component companies . </P>
what types of stocks make up the s&p 500
what types of stocks make up the s&p 500
common
common