IBB vs RCUS: Correlation
How closely do iShares Biotechnology ETF (IBB) and Arcus Biosciences, Inc. (RCUS) trade together? Their weekly returns over three years give a correlation of 0.59, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are IBB and RCUS?
On 3 years of weekly data the IBB/RCUS correlation comes out at 0.59, moderate. Recent behaviour matches the longer record: 0.50 over 1 year against 0.59 over 3. The 5-year figure is 0.49, and annualized covariance runs at 717.4 %².
By 3-year correlation, RCUS places #40 of the 168 assets tracked against IBB. The last year tells two different stories: RCUS led by 134.3 percentage points, +55.4% for IBB against +189.7% for RCUS. Note the risk asymmetry: RCUS runs 2.9 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.
IBB vs RCUS: side by side
| IBB (iShares Biotechnology ETF) | RCUS (Arcus Biosciences, Inc.) | |
|---|---|---|
| 1-year return | +55.4% | +189.7% |
| 5-year return | +26.6% | +3.1% |
| Volatility (ann.) | 20.7% | 59.0% |
| Beta vs S&P 500 | 0.81 | 1.71 |
| Max drawdown (3Y) | -24.9% | -69.5% |
| Market cap | – | $3.8B |
| P/E (trailing) | – | – |
| Dividend yield | 0.22% | 0.00% |
| Expense ratio | 0.44% | – |
| Assets under management | $9.2B | – |
| Sector / category | ETF · Thematic | US Listed |
IBB is a Health fund from iShares: $9.2B under management, 235 holdings, a 0.44% expense ratio, a 0.22% trailing dividend yield.
Year-by-year returns
| Year | IBB | RCUS |
|---|---|---|
| 2022 | -13.7% | -48.9% |
| 2023 | +3.8% | -7.6% |
| 2024 | -2.4% | -22.0% |
| 2025 | +28.0% | +60.0% |
| 2026 | +27.4% | +28.4% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Fund exposure
Keep in mind that IBB holds RCUS at a 0.18% weight, which makes a slice of this correlation mechanical rather than coincidental.
Are IBB and RCUS good diversifiers for each other?
Somewhat, no more. With 0.59 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between IBB and RCUS?
The IBB/RCUS correlation stands at 0.59 on a 3-year window (1 year: 0.50, 5 years: 0.49), computed from weekly returns as of 2026-08-27.
Is RCUS a good diversifier for IBB?
Somewhat, no more. With 0.59 correlation, most large moves hit both names, and the diversification benefit stays modest.
What does a correlation of 0.59 mean?
On the −1 to +1 scale, 0.59 describes how much the two returns move together: +1 is lockstep, 0 is independence, negative values mean opposite directions. It says nothing about which performed better.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/ibb-vs-rcus.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/ibb-vs-rcus/)
The core API is free. Terms and every endpoint in the API documentation.
Related comparisons
Hubs: IBB correlations · RCUS correlations
