BSX vs SPY: Correlation
How closely do Boston Scientific (BSX) and SPDR S&P 500 ETF Trust (SPY) trade together? Their weekly returns over three years give a correlation of 0.38, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are BSX and SPY?
Across a 3-year window, the weekly returns of BSX and SPY correlate at 0.38, moderate. The past 12 months show a weaker link (0.15) than the 3-year average (0.38). Stretching to 5 years gives 0.49, with an annualized covariance of 149.7 %².
Within BSX's tracked universe of 33 assets, SPY comes in at #17 by 3-year correlation. Their recent paths diverged sharply: over the last 12 months SPY outperformed by 76.5 percentage points (-55.9% for BSX against +20.6% for SPY). Do not treat this figure as fixed: across three years the rolling one-year correlation ranged all the way from 0.11 to 0.76. Note the risk asymmetry: BSX runs 1.9 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.
BSX vs SPY: side by side
| BSX (Boston Scientific) | SPY (SPDR S&P 500 ETF Trust) | |
|---|---|---|
| 1-year return | -55.9% | +20.6% |
| 5-year return | +4.1% | +82.4% |
| Volatility (ann.) | 27.6% | 14.5% |
| Beta vs S&P 500 | 0.72 | 1.00 |
| Max drawdown (3Y) | -60.6% | -18.8% |
| Market cap | $67.6B | – |
| P/E (trailing) | 19.5 | – |
| Dividend yield | 0.00% | 1.01% |
| Expense ratio | – | 0.09% |
| Assets under management | – | $795.3B |
| Sector / category | Health Care | ETF · US Large Cap |
SPY is a Large Blend fund from State Street Investment Management: $795.3B under management, 504 holdings, a 0.09% expense ratio, a 1.01% trailing dividend yield.
Year-by-year returns
| Year | BSX | SPY |
|---|---|---|
| 2022 | +8.9% | -18.2% |
| 2023 | +24.9% | +26.2% |
| 2024 | +54.5% | +24.9% |
| 2025 | +6.8% | +17.7% |
| 2026 | -51.1% | +13.7% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Fund exposure
Keep in mind that SPY holds BSX at a 0.11% weight, which makes a slice of this correlation mechanical rather than coincidental.
Are BSX and SPY good diversifiers for each other?
Yes, to a useful degree: a correlation of 0.38 leaves real independence between the two, which historically damped combined volatility.
FAQ
What is the correlation between BSX and SPY?
The BSX/SPY correlation stands at 0.38 on a 3-year window (1 year: 0.15, 5 years: 0.49), computed from weekly returns as of 2026-08-27.
Is SPY a good diversifier for BSX?
Yes, to a useful degree: a correlation of 0.38 leaves real independence between the two, which historically damped combined volatility.
What does a correlation of 0.38 mean?
A reading of 0.38 sits on a scale from −1 (opposite moves) through 0 (unrelated) to +1 (identical moves). Correlation captures direction, not magnitude or performance.
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Hubs: BSX correlations · SPY correlations
