S&P 500 (or ^SPX, which represents Standard and Poor's 500) is an American stock market index. The top 500 companies that have common stock market capitalizations listed on NASDAQ or the New York Stock Exchange are showcased on the index. With offices in 23 countries, Standard and Poor maintains the S&P 500 index from their headquarters in New York. S&P 500 indexes more than $1.25 trillion USD in their portfolio. On the NYSE, the S&P 500 index lists the status of the entire stock market by monitoring the volatility and return of the 500 most frequently held large-cap business stocks, capturing about 80% of the entire market capitalization.