IBB vs PTCT: Correlation
Measured on weekly returns over the past three years, iShares Biotechnology ETF (IBB) and PTC Therapeutics, Inc. (PTCT) carry a correlation of 0.50, a moderate link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are IBB and PTCT?
Over the past 3 years, IBB and PTCT moved with a correlation of 0.50, which is moderate. Little has changed lately, as the 1-year reading of 0.56 lands near the 3-year figure. Over 5 years the correlation is 0.53, and the annualized covariance of weekly returns is 548.9 %².
By 3-year correlation, PTCT places #96 of the 168 assets tracked against IBB. The trailing year gives IBB the advantage: +55.4% versus +44.3%, a 11.1-point spread. One caveat on sizing: PTCT is 2.5 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 PTCT: side by side
| IBB (iShares Biotechnology ETF) | PTCT (PTC Therapeutics, Inc.) | |
|---|---|---|
| 1-year return | +55.4% | +44.3% |
| 5-year return | +26.6% | +70.4% |
| Volatility (ann.) | 20.7% | 52.5% |
| Beta vs S&P 500 | 0.81 | 1.25 |
| Max drawdown (3Y) | -24.9% | -56.8% |
| Market cap | – | $6.0B |
| 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 | PTCT |
|---|---|---|
| 2022 | -13.7% | -4.2% |
| 2023 | +3.8% | -27.8% |
| 2024 | -2.4% | +63.8% |
| 2025 | +28.0% | +68.3% |
| 2026 | +27.4% | -5.5% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Fund exposure
A structural note: 0.4% of IBB is PTCT itself, so the fund partly moves with the stock by construction.
Are IBB and PTCT good diversifiers for each other?
Only partially. A correlation of 0.50 means IBB and PTCT 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 PTCT?
Using weekly returns as of 2026-08-27: 0.50 over 3 years, with 0.56 over the last year and 0.53 over 5 years.
Is PTCT a good diversifier for IBB?
Only partially. A correlation of 0.50 means IBB and PTCT share most of their swings. Pairing them dampens volatility somewhat, but it will not protect against a common drawdown.
What does a correlation of 0.50 mean?
A reading of 0.50 sits on a scale from −1 (opposite moves) through 0 (unrelated) to +1 (identical moves). Correlation captures direction, not magnitude or performance.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/ibb-vs-ptct.json
Markdown for the live badge, attribution link included:
[](https://www.pairbook.io/pair/ibb-vs-ptct/)
No key needed, free to use. Full endpoint list in the API documentation.
Related comparisons
Hubs: IBB correlations · PTCT correlations
