S&P 500
The S&P 500 is a stock market index of about 500 leading US companies, weighted by float-adjusted market capitalization and widely used as a benchmark.
The Standard & Poor's 500, usually called the S&P 500, tracks the stocks of roughly 500 large companies listed in the United States. Because it covers a large part of the total value of the US stock market, it is the most common benchmark for US stocks and for many investment funds.
The index is maintained by S&P Dow Jones Indices. Unlike some indices that automatically include the largest companies, the S&P 500 is selected by a committee based on criteria such as market cap, liquidity, public float, US domicile and a record of positive earnings. Because some companies have more than one share class, the index has slightly more than 500 constituents.
The S&P 500 is weighted by float-adjusted market capitalization, so the largest companies have the most influence on its movements. It covers all eleven major sectors of the economy.
The headline index is a price index. A total return version also includes reinvested dividends, which makes a meaningful difference over long periods.
Many index funds and ETFs track the S&P 500, making it one of the most widely held investments in the world.