S&P 500 Index

The S&P 500 is a stock index that condenses the share performance of large companies listed on US exchanges into a single point value. Calculated by S&P Dow Jones Indices, the index began publication in its current form in 1957. Constituents are weighted by company value adjusted for free float, so moves in higher-valued companies have a greater effect on the index.

Index membership is not decided by size alone. An index committee selects companies by assessing criteria such as liquidity, public float, profitability and US domicile. Because it covers every sector, including technology, health care, financials, energy and consumer businesses, the S&P 500 is followed as a gauge that sums up the overall direction of the US stock market, and many investment funds compare their performance against it.

On Lzzo.com, the S&P 500 is shown in points using data sourced from Yahoo Finance; it is not a currency price. The index itself cannot be bought or sold directly. Futures contracts, options and exchange-traded funds linked to it are separate products, and their prices can differ from the index level.