Russell 2000

The Russell 2000 tracks 2,000 small-cap US stocks and is the standard benchmark for small-cap performance, the way the S&P 500 is the standard for large caps. It is reconstituted once a year, when companies that have grown too large roll out and newly-qualifying small caps roll in.

Small caps as a group tend to be more sensitive to domestic interest rates and economic growth than the multinational giants that dominate the S&P 500, so the Russell 2000 often diverges sharply from large-cap indexes during rate-hiking cycles or growth scares.