spx

SPX commonly denotes the S&P 500 Index, a stock market index that tracks the performance of 500 large-cap U.S. companies. It is designed to serve as a representative benchmark for the overall U.S. equity market.

Calculation and constituents: The index is capitalization-weighted by free-float-adjusted market capitalization and is maintained by S&P Dow Jones Indices, a division of S&P Global. Constituents are selected by a committee and aim to reflect about 80% of the total U.S. stock market by value. The index uses a base value of 10 and a base date of March 4, 1957; changes to the index are implemented through an adjustable divisor to keep the scale consistent.

Trading and usage: SPX serves as a benchmark for portfolios and performance comparisons. It underpins a wide range of products, including index options and futures on the S&P 500, with SPX options traded on the CBOE and settled in cash based on the index value. The most widely known tradable exposure to the index is the SPDR S&P 500 ETF Trust, ticker SPY, along with other index trackers.

Related indices: The price-return SPX is complemented by the S&P 500 Total Return Index (SPXTR), which includes dividend reinvestment and reflects a higher level of return over time.

History: The S&P 500 was introduced in 1957 by Standard & Poor's and has since become one of the most closely watched indicators of U.S. equity performance and a central benchmark for financial markets.