The Standard and Poor's 500, or simply the S&P 500, is a stock market index tracking the performance of 500 large companies listed on stock exchanges in the United States. It is one of the most commonly followed equity indices. Wikipedia Market cap: US$42.4 trillion; (as of January 3, 2022) Constituents: 505 Related indices: S&P 1500; S&P Global 1200; S&P 100 Weighting method: Free-float capitalization-weighted Exchanges: NYSE; NASDAQ; Cboe BZX Exchange Foundation: March 4, 1957; 65 years ago