Zale would want to C. compare his stock portfolio’s performance to a benchmarking index such as the S&P 500. The S&P 500 is also known as the S&P. The S&P is the American stock market index that is based on 500 large companies. These 500 large companies are often called the fortune 500, as they are the top 500 grossing companies in the United States. Comparing your stock to these companies, would allow you to know where you stand and how your investments are doing.