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. As of December 31, 2020, more than $5.4 trillion was invested in assets tied to the performance of the index.The S&P 500 index is a free-float weighted/capitalization-weighted index. As of September 30, 2021, the nine largest companies on the list of S&P 500 companies accounted for 28.1% of the market capitalization of the index and were, in order of weighting, Apple, Microsoft, Alphabet (including both class A & C shares), Amazon.com, Meta Platforms, Tesla, Nvidia, Berkshire Hathaway and JPMorgan Chase. The components that have increased their dividends in 25 consecutive years are known as the S&P 500 Dividend Aristocrats.: 25 In 2017, companies in the index derived on average 72% of their revenue in the United States.The index is one of the factors in computation of the Conference Board Leading Economic Index, used to forecast the direction of the economy.The index is associated with many ticker symbols, including ^GSPC, INX, and $SPX, depending on market or website.The S&P 500 is maintained by S&P Dow Jones Indices, a joint venture majority-owned by S&P Global, and its components are selected by a committee.