ATI vs MDY: Correlation
ATI Inc. (ATI) and SPDR S&P MidCap 400 ETF (MDY) show a strong relationship: their 3-year correlation of weekly returns is 0.63.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are ATI and MDY?
Over the past 3 years, ATI and MDY moved with a correlation of 0.63, which is strong. Little has changed lately, as the 1-year reading of 0.61 lands near the 3-year figure. Over 5 years the correlation is 0.61, and the annualized covariance of weekly returns is 451.3 %².
Within ATI's tracked universe of 12 assets, MDY comes in at #4 by 3-year correlation. The last year tells two different stories: ATI led by 161.2 percentage points, +179.5% for ATI against +18.3% for MDY. Note the risk asymmetry: ATI runs 2.6 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.
ATI vs MDY: side by side
| ATI (ATI Inc.) | MDY (SPDR S&P MidCap 400 ETF) | |
|---|---|---|
| 1-year return | +179.5% | +18.3% |
| 5-year return | +1095.8% | +47.5% |
| Volatility (ann.) | 43.3% | 16.5% |
| Beta vs S&P 500 | 1.59 | 0.91 |
| Max drawdown (3Y) | -38.0% | -24.0% |
| Market cap | $29.2B | – |
| P/E (trailing) | 62.5 | – |
| Dividend yield | 0.00% | 1.02% |
| Expense ratio | – | 0.23% |
| Assets under management | – | $26.5B |
| Sector / category | US Listed | 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 | ATI | MDY |
|---|---|---|
| 2022 | +87.4% | -13.3% |
| 2023 | +52.3% | +16.1% |
| 2024 | +21.0% | +13.6% |
| 2025 | +108.5% | +7.2% |
| 2026 | +86.9% | +16.4% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Fund exposure
ATI represents 0.8% of MDY's portfolio, so part of any move in MDY is ATI itself, and the correlation between them is partly mechanical.
Are ATI and MDY good diversifiers for each other?
Only partially. A correlation of 0.63 means ATI 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 ATI and MDY?
Using weekly returns as of 2026-08-27: 0.63 over 3 years, with 0.61 over the last year and 0.61 over 5 years.
Is MDY a good diversifier for ATI?
Only partially. A correlation of 0.63 means ATI 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 0.63 mean?
Correlation ranges from −1 to +1. Values near +1 mean two assets move together, near 0 that they move independently, and negative values that they tend to move in opposite directions. It measures co-movement, not performance.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/ati-vs-mdy.json
Embed this badge (it refreshes with the data), with attribution:
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Related comparisons
Hubs: ATI correlations · MDY correlations
