MDY vs MLM: Correlation
How closely do SPDR S&P MidCap 400 ETF (MDY) and Martin Marietta Materials (MLM) trade together? Their weekly returns over three years give a correlation of 0.63, which is strong.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and MLM?
Over the past 3 years, MDY and MLM moved with a correlation of 0.63, which is strong. Little has changed lately, as the 1-year reading of 0.62 lands near the 3-year figure. Over 5 years the correlation is 0.68, and the annualized covariance of weekly returns is 249.7 %².
Within MDY's tracked universe of 359 assets, MLM comes in at #139 by 3-year correlation. The last year tells two different stories: MDY led by 32.1 percentage points, +18.3% for MDY against -13.8% for MLM. The rolling one-year correlation stayed in a tight band between 0.56 and 0.72 over the past three years, which points to a structural rather than episodic relationship.
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 MLM: side by side
| MDY (SPDR S&P MidCap 400 ETF) | MLM (Martin Marietta Materials) | |
|---|---|---|
| 1-year return | +18.3% | -13.8% |
| 5-year return | +47.5% | +42.4% |
| Volatility (ann.) | 16.5% | 23.9% |
| Beta vs S&P 500 | 0.91 | 0.85 |
| Max drawdown (3Y) | -24.0% | -26.8% |
| Market cap | – | $37.5B |
| P/E (trailing) | – | 34.4 |
| Dividend yield | 1.02% | 0.62% |
| Expense ratio | 0.23% | – |
| Assets under management | $26.5B | – |
| Sector / category | ETF · US Small & Mid Cap | Materials |
MDY is a Mid-Cap Blend fund from State Street Investment Management: $26.5B under management, 400 holdings, a 0.23% expense ratio, a 1.02% trailing dividend yield.
Year-by-year returns
| Year | MDY | MLM |
|---|---|---|
| 2022 | -13.3% | -22.7% |
| 2023 | +16.1% | +48.6% |
| 2024 | +13.6% | +4.1% |
| 2025 | +7.2% | +21.3% |
| 2026 | +16.4% | -14.9% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and MLM good diversifiers for each other?
To a limited degree. At 0.63 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
FAQ
What is the correlation between MDY and MLM?
As of 2026-08-27, the correlation of weekly returns between MDY and MLM is 0.63 over 3 years, 0.62 over 1 year and 0.68 over 5 years.
Is MLM a good diversifier for MDY?
To a limited degree. At 0.63 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
What does a correlation of 0.63 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.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/mdy-vs-mlm.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/mdy-vs-mlm/)
No key needed, free to use. Full endpoint list in the API documentation.
Related comparisons
Hubs: MDY correlations · MLM correlations
