The S&P 500 is a broad market index that follows 500 leading publicly traded companies in the United States. Its constituents span the major sectors of the economy, and each company is weighted by its publicly available market value. Investors commonly use the index as a benchmark for large-cap U.S. equities and as a reference for index funds, exchange-traded funds, and long-term portfolio performance. The constituent list changes over time as companies grow, merge, or no longer meet the index methodology.
