CMI vs MDY: Correlation
Cummins (CMI) and SPDR S&P MidCap 400 ETF (MDY) show a strong relationship: their 3-year correlation of weekly returns is 0.62.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are CMI and MDY?
Across a 3-year window, the weekly returns of CMI and MDY correlate at 0.62, strong. The link has loosened recently: the 1-year correlation (0.41) runs below the 3-year figure (0.62). Stretching to 5 years gives 0.66, with an annualized covariance of 264.2 %².
By 3-year correlation, MDY places #7 of the 36 assets tracked against CMI. The last year tells two different stories: CMI led by 26.8 percentage points, +45.1% for CMI against +18.3% for MDY. The rolling one-year correlation moved between 0.39 and 0.83 over the past three years, a moderate range. Note the risk asymmetry: CMI runs 1.6 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.
CMI vs MDY: side by side
| CMI (Cummins) | MDY (SPDR S&P MidCap 400 ETF) | |
|---|---|---|
| 1-year return | +45.1% | +18.3% |
| 5-year return | +169.6% | +47.5% |
| Volatility (ann.) | 25.9% | 16.5% |
| Beta vs S&P 500 | 1.05 | 0.91 |
| Max drawdown (3Y) | -30.5% | -24.0% |
| Market cap | $79.0B | – |
| P/E (trailing) | 29.6 | – |
| Dividend yield | 1.38% | 1.02% |
| Expense ratio | – | 0.23% |
| Assets under management | – | $26.5B |
| Sector / category | Industrials | ETF · US Small & Mid Cap |
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 | CMI | MDY |
|---|---|---|
| 2022 | +14.1% | -13.3% |
| 2023 | +1.7% | +16.1% |
| 2024 | +48.9% | +13.6% |
| 2025 | +49.4% | +7.2% |
| 2026 | +13.6% | +16.4% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are CMI and MDY good diversifiers for each other?
Somewhat, no more. With 0.62 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between CMI and MDY?
Using weekly returns as of 2026-08-27: 0.62 over 3 years, with 0.41 over the last year and 0.66 over 5 years.
Is MDY a good diversifier for CMI?
Somewhat, no more. With 0.62 correlation, most large moves hit both names, and the diversification benefit stays modest.
What does a correlation of 0.62 mean?
On the −1 to +1 scale, 0.62 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.
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Related comparisons
Hubs: CMI correlations · MDY correlations
