The Russell Top 50 Index also known as the Russell Top 50 Mega Cap is a stock market index that measures the performance of the largest companies in the Russell 3000 Index.
It includes approximately 50 of the largest securities based on a combination of their market cap and current index membership and represents approximately 40% of the total market capitalization of the Russell 3000.
The index, which was launched on January 1, 2005, is maintained by FTSE Russell, a subsidiary of the London Stock Exchange Group.
Prior to January 27, 2016, the index was tracked by an exchange-traded fund, the Guggenheim Russell Top 50 Mega Cap ETF (NYSE Arca: XLG).
[1] The ETF switched to the S&P 500 Top 50 Index.