What Is the S&P 500 Index?
The Standard & Poor's 500 Index (S&P 500) is a market-capitalization-weighted index of the 500 leading publicly traded companies in the U.S. While it assumed its present size (and name) in 1957, the S&P actually dates back to the 1920s, becoming a composite index tracking 90 stocks in 1926.1 The average annualized return since its inception in 1928 through Dec. 31, 2022, is 9.82%.2 The average annualized return since adopting 500 stocks into the index in 1957 through Dec. 31, 2022, is 10.15%.3
