SPY vs WST: Correlation
Measured on weekly returns over the past three years, SPDR S&P 500 ETF Trust (SPY) and West Pharmaceutical Services (WST) carry a correlation of 0.32, a moderate link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are SPY and WST?
Across a 3-year window, the weekly returns of SPY and WST correlate at 0.32, moderate. Recent behaviour matches the longer record: 0.32 over 1 year against 0.32 over 3. Stretching to 5 years gives 0.45, with an annualized covariance of 180.1 %².
Among the 4755 assets we track against SPY, WST ranks #2020 by 3-year correlation. The last year tells two different stories: WST led by 20.5 percentage points, +20.6% for SPY against +41.1% for WST. This link changes with the market regime, having swung between 0.05 and 0.59 on a rolling one-year basis. One caveat on sizing: WST is 2.7 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.
SPY vs WST: side by side
| SPY (SPDR S&P 500 ETF Trust) | WST (West Pharmaceutical Services) | |
|---|---|---|
| 1-year return | +20.6% | +41.1% |
| 5-year return | +82.4% | -22.4% |
| Volatility (ann.) | 14.5% | 38.6% |
| Beta vs S&P 500 | 1.00 | 0.86 |
| Max drawdown (3Y) | -18.8% | -53.8% |
| Market cap | – | $24.4B |
| P/E (trailing) | – | 44.8 |
| Dividend yield | 1.01% | 0.25% |
| Expense ratio | 0.09% | – |
| Assets under management | $795.3B | – |
| Sector / category | ETF · US Large Cap | Health Care |
On the fund side, SPY sits in the Large Blend category at State Street Investment Management, with $795.3B under management, 504 holdings, a 0.09% expense ratio, a 1.01% trailing dividend yield.
Year-by-year returns
| Year | SPY | WST |
|---|---|---|
| 2022 | -18.2% | -49.7% |
| 2023 | +26.2% | +50.0% |
| 2024 | +24.9% | -6.8% |
| 2025 | +17.7% | -15.7% |
| 2026 | +13.7% | +26.1% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are SPY and WST good diversifiers for each other?
A fair diversifier. At 0.32, enough of each asset's movement is its own that the pair has smoothed outcomes historically.
FAQ
What is the correlation between SPY and WST?
Using weekly returns as of 2026-08-27: 0.32 over 3 years, with 0.32 over the last year and 0.45 over 5 years.
Is WST a good diversifier for SPY?
A fair diversifier. At 0.32, enough of each asset's movement is its own that the pair has smoothed outcomes historically.
What does a correlation of 0.32 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/spy-vs-wst.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/spy-vs-wst/)
No key needed, free to use. Full endpoint list in the API documentation.
Related comparisons
Hubs: SPY correlations · WST correlations
