RARE vs XBI: Correlation
Ultragenyx Pharmaceutical Inc. (RARE) and SPDR S&P Biotech ETF (XBI) show a strong relationship: their 3-year correlation of weekly returns is 0.63.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are RARE and XBI?
Across a 3-year window, the weekly returns of RARE and XBI correlate at 0.63, strong. The relationship has been stable: the 1-year correlation (0.70) sits close to the 3-year figure. Stretching to 5 years gives 0.63, with an annualized covariance of 891.3 %².
Few assets follow RARE as closely as XBI, which ranks #1 of 14 tracked partners. The last year tells two different stories: XBI led by 99.9 percentage points, -12.7% for RARE against +87.2% for XBI. Note the risk asymmetry: RARE runs 1.8 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.
RARE vs XBI: side by side
| RARE (Ultragenyx Pharmaceutical Inc.) | XBI (SPDR S&P Biotech ETF) | |
|---|---|---|
| 1-year return | -12.7% | +87.2% |
| 5-year return | -72.6% | +28.6% |
| Volatility (ann.) | 51.1% | 27.7% |
| Beta vs S&P 500 | 1.38 | 1.09 |
| Max drawdown (3Y) | -68.8% | -33.0% |
| Market cap | $2.6B | – |
| P/E (trailing) | – | – |
| Dividend yield | 0.00% | – |
| Sector / category | US Listed | ETF · Thematic |
Year-by-year returns
| Year | RARE | XBI |
|---|---|---|
| 2022 | -44.9% | -25.9% |
| 2023 | +3.2% | +7.6% |
| 2024 | -12.0% | +1.0% |
| 2025 | -45.3% | +35.9% |
| 2026 | +14.2% | +38.1% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are RARE and XBI good diversifiers for each other?
Somewhat, no more. With 0.63 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between RARE and XBI?
As of 2026-08-27, the correlation of weekly returns between RARE and XBI is 0.63 over 3 years, 0.70 over 1 year and 0.63 over 5 years.
Is XBI a good diversifier for RARE?
Somewhat, no more. With 0.63 correlation, most large moves hit both names, and the diversification benefit stays modest.
What does a correlation of 0.63 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/rare-vs-xbi.json
Embed this badge (it refreshes with the data), with attribution:
[](https://www.pairbook.io/pair/rare-vs-xbi/)
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Related comparisons
Hubs: RARE correlations · XBI correlations
