S&P_100 =The S&P 100 Index is a stock market index of United States stocks maintained by Standard & Poor's.
Index options on the S&P 100 are traded with the ticker symbol 'OEX'. Because of the popularity of these options, investors often refer to the index by its ticker symbol.
The S&P 100, a subset of the S&P 500, includes 101 (because one of its component companies has 2 classes of stock) leading U.S. stocks with exchange-listed options. Constituents of the S&P 100 are selected for sector balance and represent about 63% of the market capitalization of the S&P 500 and almost 51% of the market capitalization of the U.S. equity markets as of January 2017. The stocks in the S&P 100 tend to be the largest and most established companies in the S&P 500.