The S&P 500 (SPX) Standard and Poor’s 500 is a freely weighted portfolio measurement index of 500 of the biggest bond firms in the US. It is one of the most often used stock indexes.

The S&P 500 index is a capitalization-weighted index and 27,5% of the market capitalization of the index is made up of the top ten stocks. Apple Inc., Microsoft, Amazon.com, Facebook, Alphabet Inc. (class A & C), Tesla, Inc., Berkshire Hathaway, JPMorgan Chase & Co., and Johnson & Johnson were among the ten most important firms inside the index in terms of weighting. See S&P 500 firms for a list of components of the index.