IRM vs MDY: Correlation
Iron Mountain (IRM) and SPDR S&P MidCap 400 ETF (MDY) show a moderate relationship: their 3-year correlation of weekly returns is 0.52.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are IRM and MDY?
Over the past 3 years, IRM and MDY moved with a correlation of 0.52, which is moderate. Little has changed lately, as the 1-year reading of 0.44 lands near the 3-year figure. Over 5 years the correlation is 0.58, and the annualized covariance of weekly returns is 265.7 %².
Among the 31 assets we track against IRM, MDY ranks #14 by 3-year correlation. Their recent paths diverged sharply: over the last 12 months IRM outperformed by 19.8 percentage points (+38.1% for IRM against +18.3% for MDY). On a rolling one-year basis the correlation drifted between 0.31 and 0.80, a moderate band. Risk is not evenly split, since IRM carries 1.9 times the volatility of the other side.
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.
IRM vs MDY: side by side
| IRM (Iron Mountain) | MDY (SPDR S&P MidCap 400 ETF) | |
|---|---|---|
| 1-year return | +38.1% | +18.3% |
| 5-year return | +219.3% | +47.5% |
| Volatility (ann.) | 30.8% | 16.5% |
| Beta vs S&P 500 | 0.96 | 0.91 |
| Max drawdown (3Y) | -39.0% | -24.0% |
| Market cap | $36.5B | – |
| P/E (trailing) | 86.4 | – |
| Dividend yield | 2.78% | 1.02% |
| Expense ratio | – | 0.23% |
| Assets under management | – | $26.5B |
| Sector / category | Real Estate | 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 | IRM | MDY |
|---|---|---|
| 2022 | -0.1% | -13.3% |
| 2023 | +46.5% | +16.1% |
| 2024 | +54.5% | +13.6% |
| 2025 | -18.2% | +7.2% |
| 2026 | +50.1% | +16.4% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are IRM and MDY good diversifiers for each other?
Somewhat, no more. With 0.52 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between IRM and MDY?
As of 2026-08-27, the correlation of weekly returns between IRM and MDY is 0.52 over 3 years, 0.44 over 1 year and 0.58 over 5 years.
Is MDY a good diversifier for IRM?
Somewhat, no more. With 0.52 correlation, most large moves hit both names, and the diversification benefit stays modest.
What does a correlation of 0.52 mean?
On the −1 to +1 scale, 0.52 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: IRM correlations · MDY correlations
