AIR vs MDY: Correlation
Measured on weekly returns over the past three years, AAR Corp. (AIR) and SPDR S&P MidCap 400 ETF (MDY) carry a correlation of 0.54, a moderate link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are AIR and MDY?
On 3 years of weekly data the AIR/MDY correlation comes out at 0.54, moderate. Recent behaviour matches the longer record: 0.63 over 1 year against 0.54 over 3. The 5-year figure is 0.60, and annualized covariance runs at 334.7 %².
In AIR's tracked universe of 10 assets, MDY sits right near the top at #1. Correlation aside, the last 12 months split them widely, with AIR ahead by 60.9 points (+79.2% versus +18.3%). Note the risk asymmetry: AIR runs 2.3 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.
AIR vs MDY: side by side
| AIR (AAR Corp.) | MDY (SPDR S&P MidCap 400 ETF) | |
|---|---|---|
| 1-year return | +79.2% | +18.3% |
| 5-year return | +302.1% | +47.5% |
| Volatility (ann.) | 37.3% | 16.5% |
| Beta vs S&P 500 | 1.06 | 0.91 |
| Max drawdown (3Y) | -35.7% | -24.0% |
| Market cap | $5.5B | – |
| P/E (trailing) | 28.0 | – |
| Dividend yield | 0.00% | 1.02% |
| Expense ratio | – | 0.23% |
| Assets under management | – | $26.5B |
| Sector / category | US Listed | 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 | AIR | MDY |
|---|---|---|
| 2022 | +15.0% | -13.3% |
| 2023 | +39.0% | +16.1% |
| 2024 | -1.8% | +13.6% |
| 2025 | +35.1% | +7.2% |
| 2026 | +64.2% | +16.4% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are AIR and MDY good diversifiers for each other?
Only partially. A correlation of 0.54 means AIR and MDY share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
FAQ
What is the correlation between AIR and MDY?
Using weekly returns as of 2026-08-27: 0.54 over 3 years, with 0.63 over the last year and 0.60 over 5 years.
Is MDY a good diversifier for AIR?
Only partially. A correlation of 0.54 means AIR and MDY share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
What does a correlation of 0.54 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: AIR correlations · MDY correlations
