IBB vs RARE: Correlation
iShares Biotechnology ETF (IBB) and Ultragenyx Pharmaceutical Inc. (RARE) show a moderate relationship: their 3-year correlation of weekly returns is 0.55.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are IBB and RARE?
Over the past 3 years, IBB and RARE moved with a correlation of 0.55, which is moderate. Recent behaviour matches the longer record: 0.56 over 1 year against 0.55 over 3. Over 5 years the correlation is 0.55, and the annualized covariance of weekly returns is 584.5 %².
By 3-year correlation, RARE places #66 of the 168 assets tracked against IBB. The last year tells two different stories: IBB led by 68.1 percentage points, +55.4% for IBB against -12.7% for RARE. Note the risk asymmetry: RARE runs 2.5 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 RARE: side by side
| IBB (iShares Biotechnology ETF) | RARE (Ultragenyx Pharmaceutical Inc.) | |
|---|---|---|
| 1-year return | +55.4% | -12.7% |
| 5-year return | +26.6% | -72.6% |
| Volatility (ann.) | 20.7% | 51.1% |
| Beta vs S&P 500 | 0.81 | 1.38 |
| Max drawdown (3Y) | -24.9% | -68.8% |
| Market cap | – | $2.6B |
| 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, iShares's Health fund, carries $9.2B under management, 235 holdings, a 0.44% expense ratio, a 0.22% trailing dividend yield.
Year-by-year returns
| Year | IBB | RARE |
|---|---|---|
| 2022 | -13.7% | -44.9% |
| 2023 | +3.8% | +3.2% |
| 2024 | -2.4% | -12.0% |
| 2025 | +28.0% | -45.3% |
| 2026 | +27.4% | +14.2% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Fund exposure
RARE represents 0.16% of IBB's portfolio, so part of any move in IBB is RARE itself, and the correlation between them is partly mechanical.
Are IBB and RARE good diversifiers for each other?
Only partially. A correlation of 0.55 means IBB and RARE share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
FAQ
What is the correlation between IBB and RARE?
Using weekly returns as of 2026-08-27: 0.55 over 3 years, with 0.56 over the last year and 0.55 over 5 years.
Is RARE a good diversifier for IBB?
Only partially. A correlation of 0.55 means IBB and RARE share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
What does a correlation of 0.55 mean?
On the −1 to +1 scale, 0.55 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-rare.json
Embed this badge (it refreshes with the data), with attribution:
[](https://www.pairbook.io/pair/ibb-vs-rare/)
No key needed, free to use. Full endpoint list in the API documentation.
Related comparisons
Hubs: IBB correlations · RARE correlations
