Apple to join S&P 100

The consumer electronics maker will replace MedImmune Inc., a biotechnology company being acquired by Anglo-Swedish group AstraZeneca Plc.

The S&P 100, a subset of the S&P 500, is comprised of 100 leading U.S. stocks with exchange-listed options.

Constituents for the index, known by the ticker symbol OEX, are selected for sector balance and represent about 57 percent of the market capitalization of the S&P 500. S&P 100 companies also account for almost 45 percent of the market capitalization of the U.S. equity markets.

Stocks in the S&P 100 are generally among the largest and most established companies in the S&P 500. In past years, turnover among stocks in the S&P 100 has been even lower than the turnover in the S&P 500.