ERII vs SPY: Correlation
How closely do Energy Recovery, Inc. (ERII) and SPDR S&P 500 ETF Trust (SPY) trade together? Their weekly returns over three years give a correlation of 0.41, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are ERII and SPY?
Across a 3-year window, the weekly returns of ERII and SPY correlate at 0.41, moderate. The past 12 months show a weaker link (0.26) than the 3-year average (0.41). Stretching to 5 years gives 0.47, with an annualized covariance of 300.3 %².
Among the 11 assets we track against ERII, SPY ranks #6 by 3-year correlation. Correlation aside, the last 12 months split them widely, with SPY ahead by 66.4 points (-45.8% versus +20.6%). One caveat on sizing: ERII is 3.5 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 SPY: side by side
| ERII (Energy Recovery, Inc.) | SPY (SPDR S&P 500 ETF Trust) | |
|---|---|---|
| 1-year return | -45.8% | +20.6% |
| 5-year return | -60.7% | +82.4% |
| Volatility (ann.) | 51.2% | 14.5% |
| Beta vs S&P 500 | 1.44 | 1.00 |
| Max drawdown (3Y) | -72.4% | -18.8% |
| Market cap | $0.4B | – |
| P/E (trailing) | 30.4 | – |
| Dividend yield | 0.00% | 1.01% |
| Expense ratio | – | 0.09% |
| Assets under management | – | $795.3B |
| Sector / category | US Listed | ETF · US Large Cap |
SPY is a Large Blend fund from State Street Investment Management: $795.3B under management, 504 holdings, a 0.09% expense ratio, a 1.01% trailing dividend yield.
Year-by-year returns
| Year | ERII | SPY |
|---|---|---|
| 2022 | -4.7% | -18.2% |
| 2023 | -8.1% | +26.2% |
| 2024 | -22.0% | +24.9% |
| 2025 | -8.2% | +17.7% |
| 2026 | -41.4% | +13.7% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are ERII and SPY good diversifiers for each other?
A fair diversifier. At 0.41, enough of each asset's movement is its own that the pair has smoothed outcomes historically.
FAQ
What is the correlation between ERII and SPY?
As of 2026-08-27, the correlation of weekly returns between ERII and SPY is 0.41 over 3 years, 0.26 over 1 year and 0.47 over 5 years.
Is SPY a good diversifier for ERII?
A fair diversifier. At 0.41, enough of each asset's movement is its own that the pair has smoothed outcomes historically.
What does a correlation of 0.41 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.
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Related comparisons
Hubs: ERII correlations · SPY correlations
