The Russell 1000 Index is a stock market index that tracks the highest-ranking 1,000 stocks in the Russell 3000 Index, which represent about 93% of the total market capitalization of that index. As of 31 December 2021, the stocks of the Russell 1000 Index had a weighted average market capitalization of $608.1 billion and a median market capitalization of $15.1 billion. As of 8 May 2020, components ranged in market capitalization from $1.8 billion to $1.4 trillion. The index, which was launched on January 1, 1984, is maintained by FTSE Russell, a subsidiary of the London Stock Exchange Group.