IBB vs PRTA: Correlation
How closely do iShares Biotechnology ETF (IBB) and Prothena Corporation plc (PRTA) trade together? Their weekly returns over three years give a correlation of 0.50, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are IBB and PRTA?
Across a 3-year window, the weekly returns of IBB and PRTA correlate at 0.50, moderate. The relationship has been stable: the 1-year correlation (0.41) sits close to the 3-year figure. Stretching to 5 years gives 0.42, with an annualized covariance of 602.3 %².
Among the 168 assets we track against IBB, PRTA ranks #95 by 3-year correlation. Correlation aside, the last 12 months split them widely, with IBB ahead by 49.2 points (+55.4% versus +6.2%). One caveat on sizing: PRTA is 2.8 times as volatile as the other leg, so an equal-dollar split is far from equal-risk.
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 PRTA: side by side
| IBB (iShares Biotechnology ETF) | PRTA (Prothena Corporation plc) | |
|---|---|---|
| 1-year return | +55.4% | +6.2% |
| 5-year return | +26.6% | -86.9% |
| Volatility (ann.) | 20.7% | 57.9% |
| Beta vs S&P 500 | 0.81 | 0.93 |
| Max drawdown (3Y) | -24.9% | -91.9% |
| Market cap | – | $0.5B |
| 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 | PRTA |
|---|---|---|
| 2022 | -13.7% | +22.0% |
| 2023 | +3.8% | -39.7% |
| 2024 | -2.4% | -61.9% |
| 2025 | +28.0% | -31.0% |
| 2026 | +27.4% | -4.8% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are IBB and PRTA good diversifiers for each other?
To a limited degree. At 0.50 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
FAQ
What is the correlation between IBB and PRTA?
The IBB/PRTA correlation stands at 0.50 on a 3-year window (1 year: 0.41, 5 years: 0.42), computed from weekly returns as of 2026-08-27.
Is PRTA a good diversifier for IBB?
To a limited degree. At 0.50 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
What does a correlation of 0.50 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
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Related comparisons
Hubs: IBB correlations · PRTA correlations
