Russell 2000

Russell 2000 tells you what the ~2,000 smallest US companies are doing. It's dominated by regional banks, domestic industrials, and biotech — so it's much more rate-sensitive than the S&P and much more exposed to the US economy (not global revenue). A widening Russell-vs-S&P spread is the classic “megacap vs real economy” story: when small-caps lag, it usually signals tight financial conditions or a domestic growth scare.