CAT vs MDY: Correlation
How closely do Caterpillar Inc. (CAT) and SPDR S&P MidCap 400 ETF (MDY) trade together? Their weekly returns over three years give a correlation of 0.61, which is strong.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are CAT and MDY?
Over the past 3 years, CAT and MDY moved with a correlation of 0.61, which is strong. Lately the two have drifted apart, with the 1-year correlation at 0.39 versus 0.61 over 3 years. Over 5 years the correlation is 0.64, and the annualized covariance of weekly returns is 295.4 %².
Among the 36 assets we track against CAT, MDY ranks #11 by 3-year correlation. Correlation aside, the last 12 months split them widely, with CAT ahead by 72.2 points (+90.5% versus +18.3%). Across three years, the rolling one-year figure varied moderately, from 0.38 to 0.80. One caveat on sizing: CAT is 1.8 times as volatile as the other leg, so an equal-dollar split is far from equal-risk.
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.
CAT vs MDY: side by side
| CAT (Caterpillar Inc.) | MDY (SPDR S&P MidCap 400 ETF) | |
|---|---|---|
| 1-year return | +90.5% | +18.3% |
| 5-year return | +321.1% | +47.5% |
| Volatility (ann.) | 29.4% | 16.5% |
| Beta vs S&P 500 | 1.03 | 0.91 |
| Max drawdown (3Y) | -34.0% | -24.0% |
| Market cap | $375.6B | – |
| P/E (trailing) | 35.3 | – |
| Dividend yield | 0.75% | 1.02% |
| Expense ratio | – | 0.23% |
| Assets under management | – | $26.5B |
| Sector / category | Industrials | ETF · US Small & Mid Cap |
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 | CAT | MDY |
|---|---|---|
| 2022 | +18.6% | -13.3% |
| 2023 | +25.9% | +16.1% |
| 2024 | +24.7% | +13.6% |
| 2025 | +60.3% | +7.2% |
| 2026 | +43.5% | +16.4% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are CAT and MDY good diversifiers for each other?
Only partially. A correlation of 0.61 means CAT and MDY 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 CAT and MDY?
Using weekly returns as of 2026-08-27: 0.61 over 3 years, with 0.39 over the last year and 0.64 over 5 years.
Is MDY a good diversifier for CAT?
Only partially. A correlation of 0.61 means CAT and MDY share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
What does a correlation of 0.61 mean?
A reading of 0.61 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/cat-vs-mdy.json
Embed this badge (it refreshes with the data), with attribution:
[](https://www.pairbook.io/pair/cat-vs-mdy/)
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Related comparisons
Hubs: CAT correlations · MDY correlations
