ERII vs RUSHA: Correlation
Measured on weekly returns over the past three years, Energy Recovery, Inc. (ERII) and Rush Enterprises, Inc. (RUSHA) carry a correlation of 0.48, a moderate link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are ERII and RUSHA?
Over the past 3 years, ERII and RUSHA moved with a correlation of 0.48, which is moderate. Lately the two have drifted apart, with the 1-year correlation at 0.33 versus 0.48 over 3 years. Over 5 years the correlation is 0.42, and the annualized covariance of weekly returns is 770.1 %².
Within ERII's tracked universe of 11 assets, RUSHA comes in at #4 by 3-year correlation. Their recent paths diverged sharply: over the last 12 months RUSHA outperformed by 77.6 percentage points (-45.8% for ERII against +31.8% for RUSHA). One caveat on sizing: ERII is 1.6 times as volatile as the other leg, so an equal-dollar split is far from equal-risk.
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.
ERII vs RUSHA: side by side
| ERII (Energy Recovery, Inc.) | RUSHA (Rush Enterprises, Inc.) | |
|---|---|---|
| 1-year return | -45.8% | +31.8% |
| 5-year return | -60.7% | +177.5% |
| Volatility (ann.) | 51.2% | 31.3% |
| Beta vs S&P 500 | 1.44 | 0.93 |
| Max drawdown (3Y) | -72.4% | -26.8% |
| Market cap | $0.4B | $8.3B |
| P/E (trailing) | 30.4 | 23.2 |
| Dividend yield | 0.00% | 0.99% |
| Sector / category | US Listed | US Listed |
Year-by-year returns
| Year | ERII | RUSHA |
|---|---|---|
| 2022 | -4.7% | -4.5% |
| 2023 | -8.1% | +46.7% |
| 2024 | -22.0% | +10.4% |
| 2025 | -8.2% | -0.2% |
| 2026 | -41.4% | +42.8% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are ERII and RUSHA good diversifiers for each other?
A fair diversifier. At 0.48, enough of each asset's movement is its own that the pair has smoothed outcomes historically.
FAQ
What is the correlation between ERII and RUSHA?
Using weekly returns as of 2026-08-27: 0.48 over 3 years, with 0.33 over the last year and 0.42 over 5 years.
Is RUSHA a good diversifier for ERII?
A fair diversifier. At 0.48, enough of each asset's movement is its own that the pair has smoothed outcomes historically.
What does a correlation of 0.48 mean?
On the −1 to +1 scale, 0.48 describes how much the two returns move together: +1 is lockstep, 0 is independence, negative values mean opposite directions. It says nothing about which performed better.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/erii-vs-rusha.json
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Related comparisons
Hubs: ERII correlations · RUSHA correlations
