IBB vs IWM: Correlation & Overlap
Measured on weekly returns over the past three years, iShares Biotechnology ETF (IBB) and iShares Russell 2000 ETF (IWM) carry a correlation of 0.66, a strong link. By holdings, the two funds overlap 11.0% by weight.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are IBB and IWM?
Over the past 3 years, IBB and IWM moved with a correlation of 0.66, which is strong. Lately the two have drifted apart, with the 1-year correlation at 0.44 versus 0.66 over 3 years. Over 5 years the correlation is 0.67, and the annualized covariance of weekly returns is 271.1 %².
Among the 168 assets we track against IBB, IWM ranks #12 by 3-year correlation. Correlation aside, the last 12 months split them widely, with IBB ahead by 27.0 points (+55.4% versus +28.4%). On a rolling one-year basis the correlation drifted between 0.49 and 0.82, a moderate band.
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 IWM: side by side
| IBB (iShares Biotechnology ETF) | IWM (iShares Russell 2000 ETF) | |
|---|---|---|
| 1-year return | +55.4% | +28.4% |
| 5-year return | +26.6% | +41.5% |
| Volatility (ann.) | 20.7% | 19.8% |
| Beta vs S&P 500 | 0.81 | 1.06 |
| Max drawdown (3Y) | -24.9% | -27.5% |
| Dividend yield | 0.22% | 0.91% |
| Expense ratio | 0.44% | 0.19% |
| Assets under management | $9.2B | $80.1B |
| Sector / category | ETF · Thematic | ETF · US Small & Mid Cap |
On the fund side, IBB sits in the Health category at iShares, with $9.2B under management, 235 holdings, a 0.44% expense ratio, a 0.22% trailing dividend yield. IWM, iShares's Small Blend fund, carries $80.1B under management, 1757 holdings, a 0.19% expense ratio, a 0.91% trailing dividend yield.
Portfolio overlap between IBB and IWM
The two portfolios are largely distinct. Weighing the shared positions, 11.0% of the two funds is identical, spread across 158 common holdings. That shared book is a large part of why the returns line up.
| Common holding | Weight in IBB | Weight in IWM |
|---|---|---|
| CYTK | 0.65% | 0.33% |
| PRAX | 0.68% | 0.30% |
| TWST | 0.62% | 0.30% |
| KRYS | 0.64% | 0.29% |
| PTGX | 0.64% | 0.29% |
| CRNX | 0.57% | 0.28% |
| ALKS | 0.55% | 0.26% |
| PCVX | 0.60% | 0.25% |
| KYMR | 0.62% | 0.25% |
| TXG | 0.50% | 0.24% |
| SYRE | 0.50% | 0.22% |
| SRRK | 0.40% | 0.21% |
| XENE | 0.40% | 0.20% |
| RYTM | 0.51% | 0.19% |
| COGT | 0.37% | 0.19% |
Largest positions held only by IBB: AMGN (8.43%), VRTX (7.89%), GILD (7.10%), REGN (5.68%), MRNA (3.76%). Only by IWM: MOGA (0.35%), UMBF (0.34%), GKOS (0.33%), EAT (0.33%), FROG (0.32%).
Overlap = sum of the smaller of the two weights across common holdings, from issuer disclosures as of 2026-08-26. Top 15 common positions shown.
Year-by-year returns
| Year | IBB | IWM |
|---|---|---|
| 2022 | -13.7% | -20.5% |
| 2023 | +3.8% | +16.8% |
| 2024 | -2.4% | +11.4% |
| 2025 | +28.0% | +12.7% |
| 2026 | +27.4% | +22.3% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are IBB and IWM good diversifiers for each other?
Somewhat, no more. With 0.66 correlation, most large moves hit both names, and the diversification benefit stays modest.
FAQ
What is the correlation between IBB and IWM?
As of 2026-08-27, the correlation of weekly returns between IBB and IWM is 0.66 over 3 years, 0.44 over 1 year and 0.67 over 5 years.
Is IWM a good diversifier for IBB?
Somewhat, no more. With 0.66 correlation, most large moves hit both names, and the diversification benefit stays modest.
How much do IBB and IWM overlap?
Per the issuers' own portfolio disclosures (2026-08-26), the overlap is 11.0% by weight over 158 common positions.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/ibb-vs-iwm.json
Drop this badge in a README or notebook; it updates with the data:
[](https://www.pairbook.io/pair/ibb-vs-iwm/)
No key needed, free to use. Full endpoint list in the API documentation.
Related comparisons
Hubs: IBB correlations · IWM correlations
