ERII vs RUSHB: Correlation
Measured on weekly returns over the past three years, Energy Recovery, Inc. (ERII) and Rush Enterprises, Inc. (RUSHB) 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 RUSHB?
Across a 3-year window, the weekly returns of ERII and RUSHB correlate at 0.48, moderate. The link has loosened recently: the 1-year correlation (0.36) runs below the 3-year figure (0.48). Stretching to 5 years gives 0.41, with an annualized covariance of 761.1 %².
By 3-year correlation, RUSHB places #5 of the 11 assets tracked against ERII. Their recent paths diverged sharply: over the last 12 months RUSHB outperformed by 77.4 percentage points (-45.8% for ERII against +31.6% for RUSHB). One caveat on sizing: ERII is 1.7 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 RUSHB: side by side
| ERII (Energy Recovery, Inc.) | RUSHB (Rush Enterprises, Inc.) | |
|---|---|---|
| 1-year return | -45.8% | +31.6% |
| 5-year return | -60.7% | +185.6% |
| Volatility (ann.) | 51.2% | 30.8% |
| Beta vs S&P 500 | 1.44 | 0.88 |
| Max drawdown (3Y) | -72.4% | -28.5% |
| Market cap | $0.4B | $9.0B |
| P/E (trailing) | 30.4 | 23.1 |
| Dividend yield | 0.00% | 0.99% |
| Sector / category | US Listed | US Listed |
Year-by-year returns
| Year | ERII | RUSHB |
|---|---|---|
| 2022 | -4.7% | +5.9% |
| 2023 | -8.1% | +43.4% |
| 2024 | -22.0% | +4.3% |
| 2025 | -8.2% | +4.8% |
| 2026 | -41.4% | +38.0% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are ERII and RUSHB good diversifiers for each other?
Yes, to a useful degree: a correlation of 0.48 leaves real independence between the two, which historically damped combined volatility.
FAQ
What is the correlation between ERII and RUSHB?
Using weekly returns as of 2026-08-27: 0.48 over 3 years, with 0.36 over the last year and 0.41 over 5 years.
Is RUSHB a good diversifier for ERII?
Yes, to a useful degree: a correlation of 0.48 leaves real independence between the two, which historically damped combined volatility.
What does a correlation of 0.48 mean?
Correlation ranges from −1 to +1. Values near +1 mean two assets move together, near 0 that they move independently, and negative values that they tend to move in opposite directions. It measures co-movement, not performance.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/erii-vs-rushb.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/erii-vs-rushb/)
Free with attribution; caching and terms are described in the API documentation.
Related comparisons
Hubs: ERII correlations · RUSHB correlations
