MDY vs PCAR: Correlation
How closely do SPDR S&P MidCap 400 ETF (MDY) and Paccar (PCAR) trade together? Their weekly returns over three years give a correlation of 0.55, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and PCAR?
On 3 years of weekly data the MDY/PCAR correlation comes out at 0.55, moderate. The relationship has been stable: the 1-year correlation (0.48) sits close to the 3-year figure. The 5-year figure is 0.61, and annualized covariance runs at 217.0 %².
Within MDY's tracked universe of 359 assets, PCAR comes in at #248 by 3-year correlation. Over the last 12 months PCAR came out ahead by 9.5 percentage points (+18.3% against +27.8%). Across three years, the rolling one-year figure varied moderately, from 0.38 to 0.69.
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 PCAR: side by side
| MDY (SPDR S&P MidCap 400 ETF) | PCAR (Paccar) | |
|---|---|---|
| 1-year return | +18.3% | +27.8% |
| 5-year return | +47.5% | +177.9% |
| Volatility (ann.) | 16.5% | 24.1% |
| Beta vs S&P 500 | 0.91 | 0.74 |
| Max drawdown (3Y) | -24.0% | -27.7% |
| Market cap | – | $66.6B |
| P/E (trailing) | – | 26.6 |
| Dividend yield | 1.02% | 1.04% |
| 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 | PCAR |
|---|---|---|
| 2022 | -13.3% | +17.0% |
| 2023 | +16.1% | +55.0% |
| 2024 | +13.6% | +10.8% |
| 2025 | +7.2% | +8.0% |
| 2026 | +16.4% | +16.5% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and PCAR good diversifiers for each other?
Only partially. A correlation of 0.55 means MDY and PCAR 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 PCAR?
Using weekly returns as of 2026-08-27: 0.55 over 3 years, with 0.48 over the last year and 0.61 over 5 years.
Is PCAR a good diversifier for MDY?
Only partially. A correlation of 0.55 means MDY and PCAR share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
What does a correlation of 0.55 mean?
On the −1 to +1 scale, 0.55 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-pcar.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/mdy-vs-pcar/)
The core API is free. Terms and every endpoint in the API documentation.
Related comparisons
Hubs: MDY correlations · PCAR correlations
