MDY vs STLD: Correlation
SPDR S&P MidCap 400 ETF (MDY) and Steel Dynamics (STLD) show a strong relationship: their 3-year correlation of weekly returns is 0.64.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and STLD?
Over the past 3 years, MDY and STLD moved with a correlation of 0.64, which is strong. Little has changed lately, as the 1-year reading of 0.54 lands near the 3-year figure. Over 5 years the correlation is 0.64, and the annualized covariance of weekly returns is 362.7 %².
Within MDY's tracked universe of 359 assets, STLD comes in at #130 by 3-year correlation. Correlation aside, the last 12 months split them widely, with STLD ahead by 61.5 points (+18.3% versus +79.8%). Across three years, the rolling one-year figure varied moderately, from 0.50 to 0.76. Note the risk asymmetry: STLD runs 2.1 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.
MDY vs STLD: side by side
| MDY (SPDR S&P MidCap 400 ETF) | STLD (Steel Dynamics) | |
|---|---|---|
| 1-year return | +18.3% | +79.8% |
| 5-year return | +47.5% | +262.0% |
| Volatility (ann.) | 16.5% | 34.5% |
| Beta vs S&P 500 | 0.91 | 1.13 |
| Max drawdown (3Y) | -24.0% | -28.7% |
| Market cap | – | $33.8B |
| P/E (trailing) | – | 21.4 |
| Dividend yield | 1.02% | 0.87% |
| Expense ratio | 0.23% | – |
| Assets under management | $26.5B | – |
| Sector / category | ETF · US Small & Mid Cap | Materials |
On the fund side, MDY sits in the Mid-Cap Blend category at State Street Investment Management, with $26.5B under management, 400 holdings, a 0.23% expense ratio, a 1.02% trailing dividend yield.
Year-by-year returns
| Year | MDY | STLD |
|---|---|---|
| 2022 | -13.3% | +60.1% |
| 2023 | +16.1% | +22.8% |
| 2024 | +13.6% | -2.0% |
| 2025 | +7.2% | +50.7% |
| 2026 | +16.4% | +39.9% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and STLD good diversifiers for each other?
Only partially. A correlation of 0.64 means MDY and STLD 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 MDY and STLD?
Using weekly returns as of 2026-08-27: 0.64 over 3 years, with 0.54 over the last year and 0.64 over 5 years.
Is STLD a good diversifier for MDY?
Only partially. A correlation of 0.64 means MDY and STLD share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
What does a correlation of 0.64 mean?
On the −1 to +1 scale, 0.64 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-stld.json
Embed this badge (it refreshes with the data), with attribution:
[](https://www.pairbook.io/pair/mdy-vs-stld/)
The core API is free. Terms and every endpoint in the API documentation.
Related comparisons
Hubs: MDY correlations · STLD correlations
