The term S&P 500 Top 50 refers to an index that includes the mega cap stocks found in the S&P 500 Index. The S&P 500 Top 50 is published and maintained by S&P Dow Jones Indices.
The S&P 500 is believed to be the best single gauge of large-cap United States equities. The S&P 500 is a portfolio of five hundred common stocks believed to be representative of the largest, and most stable, common stock traded in the U.S. market. At the time of inclusion, the market capitalization of these securities was in excess of $5.3 billion.
First launched on November 30, 2005, the S&P 500 Top 50 is designed to provide investors with a measure of the performance of the mega-cap U.S. equity market. Companies are selected based on float-adjusted market capitalization. At the time of this writing, the median market cap of the securities in this index was $183 billion.