MDY vs WAB: Correlation
SPDR S&P MidCap 400 ETF (MDY) and Wabtec (WAB) show a strong relationship: their 3-year correlation of weekly returns is 0.67.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and WAB?
On 3 years of weekly data the MDY/WAB correlation comes out at 0.67, strong. The link has loosened recently: the 1-year correlation (0.49) runs below the 3-year figure (0.67). The 5-year figure is 0.73, and annualized covariance runs at 278.8 %².
Within MDY's tracked universe of 359 assets, WAB comes in at #98 by 3-year correlation. Correlation aside, the last 12 months split them widely, with WAB ahead by 34.6 points (+18.3% versus +52.9%). On a rolling one-year basis the correlation drifted between 0.49 and 0.87, a moderate band. Risk is not evenly split, since WAB carries 1.5 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 WAB: side by side
| MDY (SPDR S&P MidCap 400 ETF) | WAB (Wabtec) | |
|---|---|---|
| 1-year return | +18.3% | +52.9% |
| 5-year return | +47.5% | +241.0% |
| Volatility (ann.) | 16.5% | 25.3% |
| Beta vs S&P 500 | 0.91 | 0.99 |
| Max drawdown (3Y) | -24.0% | -23.6% |
| Market cap | – | $50.2B |
| P/E (trailing) | – | 40.5 |
| Dividend yield | 1.02% | 0.37% |
| Expense ratio | 0.23% | – |
| Assets under management | $26.5B | – |
| Sector / category | ETF · US Small & Mid Cap | Industrials |
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 | WAB |
|---|---|---|
| 2022 | -13.3% | +9.1% |
| 2023 | +16.1% | +28.0% |
| 2024 | +13.6% | +50.1% |
| 2025 | +7.2% | +13.2% |
| 2026 | +16.4% | +39.8% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and WAB good diversifiers for each other?
Only partially. A correlation of 0.67 means MDY and WAB 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 WAB?
As of 2026-08-27, the correlation of weekly returns between MDY and WAB is 0.67 over 3 years, 0.49 over 1 year and 0.73 over 5 years.
Is WAB a good diversifier for MDY?
Only partially. A correlation of 0.67 means MDY and WAB share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
What does a correlation of 0.67 mean?
A reading of 0.67 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-wab.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/mdy-vs-wab/)
No key needed, free to use. Full endpoint list in the API documentation.
Related comparisons
Hubs: MDY correlations · WAB correlations
