IBB vs SPY: Correlation & Overlap
Measured on weekly returns over the past three years, iShares Biotechnology ETF (IBB) and SPDR S&P 500 ETF Trust (SPY) carry a correlation of 0.56, a moderate link. Looking through to holdings, 1.2% of the two portfolios is the same by weight.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are IBB and SPY?
On 3 years of weekly data the IBB/SPY correlation comes out at 0.56, moderate. The past 12 months show a weaker link (0.36) than the 3-year average (0.56). The 5-year figure is 0.62, and annualized covariance runs at 168.2 %².
Within IBB's tracked universe of 168 assets, SPY comes in at #59 by 3-year correlation. Their recent paths diverged sharply: over the last 12 months IBB outperformed by 34.8 percentage points (+55.4% for IBB against +20.6% for SPY). The rolling one-year correlation moved between 0.39 and 0.84 over the past three years, a moderate range.
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.
IBB vs SPY: side by side
| IBB (iShares Biotechnology ETF) | SPY (SPDR S&P 500 ETF Trust) | |
|---|---|---|
| 1-year return | +55.4% | +20.6% |
| 5-year return | +26.6% | +82.4% |
| Volatility (ann.) | 20.7% | 14.5% |
| Beta vs S&P 500 | 0.81 | 1.00 |
| Max drawdown (3Y) | -24.9% | -18.8% |
| Dividend yield | 0.22% | 1.01% |
| Expense ratio | 0.44% | 0.09% |
| Assets under management | $9.2B | $795.3B |
| Sector / category | ETF · Thematic | ETF · US Large Cap |
On the fund side, IBB sits in the Health category at iShares, with $9.2B under management, 235 holdings, a 0.44% expense ratio, a 0.22% trailing dividend yield. 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.
Portfolio overlap between IBB and SPY
The two portfolios are largely distinct, with 9 holdings in common adding up to 1.2% of fund weight. Where correlation shows the co-movement, the overlap shows its source.
| Common holding | Weight in IBB | Weight in SPY |
|---|---|---|
| AMGN | 8.43% | 0.36% |
| GILD | 7.10% | 0.28% |
| VRTX | 7.89% | 0.21% |
| REGN | 5.68% | 0.12% |
| MRNA | 3.76% | 0.08% |
| BIIB | 2.23% | 0.05% |
| INCY | 1.75% | 0.03% |
| CRL | 0.97% | 0.02% |
| TECH | 0.78% | 0.02% |
Largest positions held only by IBB: ARGX (3.76%), NTRA (3.19%), RVMD (2.83%), ILMN (2.34%), ALNY (2.19%). Only by SPY: NVDA (7.68%), AAPL (6.96%), MSFT (5.58%), AMZN (3.85%), GOOGL (3.03%).
Overlap = sum of the smaller of the two weights across common holdings, from issuer disclosures as of 2026-08-26. Top 9 common positions shown.
Year-by-year returns
| Year | IBB | SPY |
|---|---|---|
| 2022 | -13.7% | -18.2% |
| 2023 | +3.8% | +26.2% |
| 2024 | -2.4% | +24.9% |
| 2025 | +28.0% | +17.7% |
| 2026 | +27.4% | +13.7% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are IBB and SPY good diversifiers for each other?
Somewhat, no more. With 0.56 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between IBB and SPY?
The IBB/SPY correlation stands at 0.56 on a 3-year window (1 year: 0.36, 5 years: 0.62), computed from weekly returns as of 2026-08-27.
Is SPY a good diversifier for IBB?
Somewhat, no more. With 0.56 correlation, most large moves hit both names, and the diversification benefit stays modest.
How much do IBB and SPY overlap?
The two funds share 9 holdings amounting to 1.2% of weight, per issuer portfolio files dated 2026-08-26.
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