MDY vs MMM: Correlation
How closely do SPDR S&P MidCap 400 ETF (MDY) and 3M (MMM) trade together? Their weekly returns over three years give a correlation of 0.57, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and MMM?
On 3 years of weekly data the MDY/MMM correlation comes out at 0.57, moderate. Recent behaviour matches the longer record: 0.65 over 1 year against 0.57 over 3. The 5-year figure is 0.61, and annualized covariance runs at 278.2 %².
By 3-year correlation, MMM places #224 of the 359 assets tracked against MDY. Twelve-month performance is nearly a tie, at +18.3% for MDY and +16.4% for MMM. Across three years, the rolling one-year figure varied moderately, from 0.32 to 0.79. Risk is not evenly split, since MMM carries 1.8 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.
MDY vs MMM: side by side
| MDY (SPDR S&P MidCap 400 ETF) | MMM (3M) | |
|---|---|---|
| 1-year return | +18.3% | +16.4% |
| 5-year return | +47.5% | +29.9% |
| Volatility (ann.) | 16.5% | 29.8% |
| Beta vs S&P 500 | 0.91 | 0.89 |
| Max drawdown (3Y) | -24.0% | -20.7% |
| Market cap | – | $92.2B |
| P/E (trailing) | – | 31.9 |
| Dividend yield | 1.02% | 1.68% |
| Expense ratio | 0.23% | – |
| Assets under management | $26.5B | – |
| Sector / category | ETF · US Small & Mid Cap | Industrials |
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 | MDY | MMM |
|---|---|---|
| 2022 | -13.3% | -29.6% |
| 2023 | +16.1% | -3.3% |
| 2024 | +13.6% | +46.1% |
| 2025 | +7.2% | +26.4% |
| 2026 | +16.4% | +13.3% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and MMM good diversifiers for each other?
Somewhat, no more. With 0.57 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between MDY and MMM?
The MDY/MMM correlation stands at 0.57 on a 3-year window (1 year: 0.65, 5 years: 0.61), computed from weekly returns as of 2026-08-27.
Is MMM a good diversifier for MDY?
Somewhat, no more. With 0.57 correlation, most large moves hit both names, and the diversification benefit stays modest.
What does a correlation of 0.57 mean?
On the −1 to +1 scale, 0.57 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.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/mdy-vs-mmm.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/mdy-vs-mmm/)
The core API is free. Terms and every endpoint in the API documentation.
Related comparisons
Hubs: MDY correlations · MMM correlations
