MDY vs ROK: Correlation
How closely do SPDR S&P MidCap 400 ETF (MDY) and Rockwell Automation (ROK) trade together? Their weekly returns over three years give a correlation of 0.56, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and ROK?
On 3 years of weekly data the MDY/ROK correlation comes out at 0.56, moderate. Recent behaviour matches the longer record: 0.48 over 1 year against 0.56 over 3. The 5-year figure is 0.65, and annualized covariance runs at 259.8 %².
By 3-year correlation, ROK places #238 of the 359 assets tracked against MDY. The trailing year gives ROK the advantage: +18.3% versus +25.7%, a 7.4-point spread. The rolling one-year correlation moved between 0.47 and 0.83 over the past three years, a moderate range. Risk is not evenly split, since ROK carries 1.7 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 ROK: side by side
| MDY (SPDR S&P MidCap 400 ETF) | ROK (Rockwell Automation) | |
|---|---|---|
| 1-year return | +18.3% | +25.7% |
| 5-year return | +47.5% | +44.9% |
| Volatility (ann.) | 16.5% | 27.9% |
| Beta vs S&P 500 | 0.91 | 0.97 |
| Max drawdown (3Y) | -24.0% | -29.0% |
| Market cap | – | $48.2B |
| P/E (trailing) | – | 40.6 |
| Dividend yield | 1.02% | 1.26% |
| Expense ratio | 0.23% | – |
| Assets under management | $26.5B | – |
| Sector / category | ETF · US Small & Mid Cap | Industrials |
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 | ROK |
|---|---|---|
| 2022 | -13.3% | -24.8% |
| 2023 | +16.1% | +22.6% |
| 2024 | +13.6% | -6.2% |
| 2025 | +7.2% | +38.4% |
| 2026 | +16.4% | +12.4% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and ROK good diversifiers for each other?
To a limited degree. At 0.56 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 ROK?
Using weekly returns as of 2026-08-27: 0.56 over 3 years, with 0.48 over the last year and 0.65 over 5 years.
Is ROK a good diversifier for MDY?
To a limited degree. At 0.56 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 0.56 mean?
On the −1 to +1 scale, 0.56 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-rok.json
Embed this badge (it refreshes with the data), with attribution:
[](https://www.pairbook.io/pair/mdy-vs-rok/)
The core API is free. Terms and every endpoint in the API documentation.
Related comparisons
Hubs: MDY correlations · ROK correlations
