MDY vs WAT: Correlation
Measured on weekly returns over the past three years, SPDR S&P MidCap 400 ETF (MDY) and Waters Corporation (WAT) carry a correlation of 0.48, a moderate link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and WAT?
Across a 3-year window, the weekly returns of MDY and WAT correlate at 0.48, moderate. Recent behaviour matches the longer record: 0.47 over 1 year against 0.48 over 3. Stretching to 5 years gives 0.52, with an annualized covariance of 277.6 %².
Among the 359 assets we track against MDY, WAT ranks #320 by 3-year correlation. Correlation aside, the last 12 months split them widely, with WAT ahead by 24.7 points (+18.3% versus +43.0%). Across three years, the rolling one-year figure varied moderately, from 0.32 to 0.73. One caveat on sizing: WAT is 2.1 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.
MDY vs WAT: side by side
| MDY (SPDR S&P MidCap 400 ETF) | WAT (Waters Corporation) | |
|---|---|---|
| 1-year return | +18.3% | +43.0% |
| 5-year return | +47.5% | +2.0% |
| Volatility (ann.) | 16.5% | 35.3% |
| Beta vs S&P 500 | 0.91 | 0.89 |
| Max drawdown (3Y) | -24.0% | -33.4% |
| Market cap | – | $41.4B |
| P/E (trailing) | – | 105.3 |
| Dividend yield | 1.02% | 0.00% |
| Expense ratio | 0.23% | – |
| Assets under management | $26.5B | – |
| Sector / category | ETF · US Small & Mid Cap | Health Care |
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 | WAT |
|---|---|---|
| 2022 | -13.3% | -8.1% |
| 2023 | +16.1% | -3.9% |
| 2024 | +13.6% | +12.7% |
| 2025 | +7.2% | +2.4% |
| 2026 | +16.4% | +10.9% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and WAT good diversifiers for each other?
Yes, to a useful degree: a correlation of 0.48 leaves real independence between the two, which historically damped combined volatility.
FAQ
What is the correlation between MDY and WAT?
Using weekly returns as of 2026-08-27: 0.48 over 3 years, with 0.47 over the last year and 0.52 over 5 years.
Is WAT a good diversifier for MDY?
Yes, to a useful degree: a correlation of 0.48 leaves real independence between the two, which historically damped combined volatility.
What does a correlation of 0.48 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
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Related comparisons
Hubs: MDY correlations · WAT correlations
