S&P500
From Reuters Financial Glossary
A major barometer of the US stock market. The S&P500 is an arithmetic index, weighted by the market capitalization (the number of a company's issued shares multiplied by their market price) of its constituents, which represents some 80 percent of the market value of all issues traded on the New York Stock Exchange. It comprises 500 shares, mainly NYSE listed firms. The CME trades futures and futures options on the index. Index options are traded at the CBOE.
