The S&P 500 is a market-cap-weighted index of 500 leading large US companies. Standard & Poor's has calculated it since 1957, and it serves as the benchmark for the US stock market.
The S&P 500 is a stock index of roughly 500 large-cap companies listed on U.S. exchanges. It is maintained by S&P Dow Jones Indices and weighted by float-adjusted market capitalization, so the largest companies have the biggest influence on the index level. Covering all eleven market sectors, it is widely regarded as the single best gauge of the overall U.S. equity market. The index has been calculated in its modern form since 1957 and serves as the benchmark for a vast amount of index funds and ETFs worldwide.
The S&P 500 is commonly read as the market's aggregate verdict on U.S. corporate earnings and economic prospects. Rising levels typically reflect improving profit expectations or greater risk appetite, while declines often signal growth worries or pressure from higher interest rates. By convention, a drop of 10% from a recent high is called a correction and a drop of 20% or more a bear market. Because the index is capitalization-weighted, a handful of mega-cap stocks can drive its moves, so the headline level does not always represent the average stock.
The main drivers are corporate earnings, Federal Reserve interest-rate policy, and macro data such as inflation and employment. Higher rates reduce the present value of future profits and tend to weigh on equities, while expectations of rate cuts often support the index. The dollar, Treasury yields, and oil prices also feed through to corporate costs and export competitiveness. Cross-checking the Nasdaq Composite, the Dow Jones Industrial Average, the VIX volatility index, and the 10-year Treasury yield gives a fuller picture of market conditions.
Daily percentage changes in the S&P 500 index. Green indicates gains, red indicates losses.
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