S&P 500 Composite Index

S&P 500 Composite Index

Index of 500 widely held common stocks that measures the general performance of the market.

Standard & Poor's 500 Index

A stock market index tracking 500 companies in various industries with a large amount of market capitalization. It is a capitalization-weighted index, meaning that stocks with higher market caps affect the average more. The companies included on the S&P 500 are decided by committee and are updated periodically. It also scales its averages to account for stock splits and other changes in the companies tracked. Next to the Dow Jones Industrial Average, it is considered one of the premier securities indices in the United States. Some exchange-traded funds, notably SPDRs, track the S&P 500.