MDY vs RUSHA: Correlation
How closely do SPDR S&P MidCap 400 ETF (MDY) and Rush Enterprises, Inc. (RUSHA) trade together? Their weekly returns over three years give a correlation of 0.64, which is strong.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and RUSHA?
Over the past 3 years, MDY and RUSHA moved with a correlation of 0.64, which is strong. Recent behaviour matches the longer record: 0.59 over 1 year against 0.64 over 3. Over 5 years the correlation is 0.63, and the annualized covariance of weekly returns is 331.8 %².
By 3-year correlation, RUSHA places #129 of the 359 assets tracked against MDY. The trailing year gives RUSHA the advantage: +18.3% versus +31.8%, a 13.5-point spread. Note the risk asymmetry: RUSHA runs 1.9 times the annualized volatility of the other leg, so equal-weighting the two is not an equal-risk position.
How is this computed?
Pearson correlation on weekly returns: ρ(A,B) = cov(rA, rB) / (σA · σB), over windows of 52, 156 and 260 weeks. Covariance is annualized (×52) and expressed in %². Full definitions on the methodology page.
MDY vs RUSHA: side by side
| MDY (SPDR S&P MidCap 400 ETF) | RUSHA (Rush Enterprises, Inc.) | |
|---|---|---|
| 1-year return | +18.3% | +31.8% |
| 5-year return | +47.5% | +177.5% |
| Volatility (ann.) | 16.5% | 31.3% |
| Beta vs S&P 500 | 0.91 | 0.93 |
| Max drawdown (3Y) | -24.0% | -26.8% |
| Market cap | – | $8.3B |
| P/E (trailing) | – | 23.2 |
| Dividend yield | 1.02% | 0.99% |
| Expense ratio | 0.23% | – |
| Assets under management | $26.5B | – |
| Sector / category | ETF · US Small & Mid Cap | US Listed |
MDY, State Street Investment Management's Mid-Cap Blend fund, carries $26.5B under management, 400 holdings, a 0.23% expense ratio, a 1.02% trailing dividend yield.
Year-by-year returns
| Year | MDY | RUSHA |
|---|---|---|
| 2022 | -13.3% | -4.5% |
| 2023 | +16.1% | +46.7% |
| 2024 | +13.6% | +10.4% |
| 2025 | +7.2% | -0.2% |
| 2026 | +16.4% | +42.8% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and RUSHA good diversifiers for each other?
To a limited degree. At 0.64 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
FAQ
What is the correlation between MDY and RUSHA?
The MDY/RUSHA correlation stands at 0.64 on a 3-year window (1 year: 0.59, 5 years: 0.63), computed from weekly returns as of 2026-08-27.
Is RUSHA a good diversifier for MDY?
To a limited degree. At 0.64 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
What does a correlation of 0.64 mean?
A reading of 0.64 sits on a scale from −1 (opposite moves) through 0 (unrelated) to +1 (identical moves). Correlation captures direction, not magnitude or performance.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/mdy-vs-rusha.json
Markdown for the live badge, attribution link included:
[](https://www.pairbook.io/pair/mdy-vs-rusha/)
Free with attribution; caching and terms are described in the API documentation.
Related comparisons
Hubs: MDY correlations · RUSHA correlations
