MDY vs NSC: Correlation
How closely do SPDR S&P MidCap 400 ETF (MDY) and Norfolk Southern (NSC) trade together? Their weekly returns over three years give a correlation of 0.58, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and NSC?
Over the past 3 years, MDY and NSC moved with a correlation of 0.58, which is moderate. The link has loosened recently: the 1-year correlation (0.25) runs below the 3-year figure (0.58). Over 5 years the correlation is 0.60, and the annualized covariance of weekly returns is 210.2 %².
Within MDY's tracked universe of 359 assets, NSC comes in at #209 by 3-year correlation. Over the last 12 months NSC came out ahead by 11.7 percentage points (+18.3% against +30.0%). On a rolling one-year basis the correlation drifted between 0.32 and 0.80, a moderate band.
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 NSC: side by side
| MDY (SPDR S&P MidCap 400 ETF) | NSC (Norfolk Southern) | |
|---|---|---|
| 1-year return | +18.3% | +30.0% |
| 5-year return | +47.5% | +49.6% |
| Volatility (ann.) | 16.5% | 22.0% |
| Beta vs S&P 500 | 0.91 | 0.69 |
| Max drawdown (3Y) | -24.0% | -25.1% |
| Market cap | – | $78.1B |
| P/E (trailing) | – | 30.1 |
| Dividend yield | 1.02% | 1.53% |
| 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 | NSC |
|---|---|---|
| 2022 | -13.3% | -15.6% |
| 2023 | +16.1% | -1.6% |
| 2024 | +13.6% | +1.6% |
| 2025 | +7.2% | +25.6% |
| 2026 | +16.4% | +22.0% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and NSC good diversifiers for each other?
Somewhat, no more. With 0.58 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between MDY and NSC?
The MDY/NSC correlation stands at 0.58 on a 3-year window (1 year: 0.25, 5 years: 0.60), computed from weekly returns as of 2026-08-27.
Is NSC a good diversifier for MDY?
Somewhat, no more. With 0.58 correlation, most large moves hit both names, and the diversification benefit stays modest.
What does a correlation of 0.58 mean?
A reading of 0.58 sits on a scale from −1 (opposite moves) through 0 (unrelated) to +1 (identical moves). Correlation captures direction, not magnitude or performance.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/mdy-vs-nsc.json
Markdown for the live badge, attribution link included:
[](https://www.pairbook.io/pair/mdy-vs-nsc/)
Free with attribution; caching and terms are described in the API documentation.
Related comparisons
Hubs: MDY correlations · NSC correlations
