MDY vs SW: Correlation
SPDR S&P MidCap 400 ETF (MDY) and Smurfit Westrock (SW) show a moderate relationship: their 3-year correlation of weekly returns is 0.58.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and SW?
Across a 3-year window, the weekly returns of MDY and SW correlate at 0.58, moderate. The relationship has been stable: the 1-year correlation (0.57) sits close to the 3-year figure. Stretching to 5 years gives 0.55, with an annualized covariance of 380.8 %².
Among the 359 assets we track against MDY, SW ranks #212 by 3-year correlation. On 12-month performance MDY holds a 8.6-point edge, +18.3% against +9.7%. The rolling one-year correlation stayed in a tight band between 0.44 and 0.69 over the past three years, which points to a structural rather than episodic relationship. Note the risk asymmetry: SW runs 2.4 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 SW: side by side
| MDY (SPDR S&P MidCap 400 ETF) | SW (Smurfit Westrock) | |
|---|---|---|
| 1-year return | +18.3% | +9.7% |
| 5-year return | +47.5% | +2.6% |
| Volatility (ann.) | 16.5% | 40.1% |
| Beta vs S&P 500 | 0.91 | 0.92 |
| Max drawdown (3Y) | -24.0% | -40.5% |
| Market cap | – | $25.5B |
| P/E (trailing) | – | 51.7 |
| Dividend yield | 1.02% | 3.57% |
| 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 | SW |
|---|---|---|
| 2022 | -13.3% | -28.0% |
| 2023 | +16.1% | +14.1% |
| 2024 | +13.6% | +37.6% |
| 2025 | +7.2% | -26.2% |
| 2026 | +16.4% | +29.5% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and SW good diversifiers for each other?
To a limited degree. At 0.58 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 SW?
As of 2026-08-27, the correlation of weekly returns between MDY and SW is 0.58 over 3 years, 0.57 over 1 year and 0.55 over 5 years.
Is SW a good diversifier for MDY?
To a limited degree. At 0.58 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 0.58 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-sw.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/mdy-vs-sw/)
Free with attribution; caching and terms are described in the API documentation.
Related comparisons
Hubs: MDY correlations · SW correlations
