IBB vs IWM: Holdings Overlap
iShares · 254 holdings · $9.3B · as of 2026-03-31
iShares · 1941 holdings · $82.2B · as of 2026-03-31
How similar are IBB and IWM?
iShares Biotechnology ETF (IBB, by iShares) holds 254 positions; iShares Russell 2000 ETF (IWM, by iShares) holds 1941. They have 172 holdings in common, and by portfolio weight the two funds are 9.7% identical. In practical terms the pair is lightly overlapping, with most of each portfolio distinct.
- Overlap by Weight
- 9.7%Sum of the smaller weight of each shared holding
- Shared Holdings
- 172IBB holds 254 · IWM holds 1941
- Weight in Shared Holdings
- IBB 27%·IWM 10%Share of each fund's weight in stocks both funds own
Based on each fund's latest official holdings. How is this calculated?
What makes each fund different
Only in IBB
82 of 254 positions (72.8% of the fund) are not held by IWM. Showing the top 30 by weight.
Sector Breakdown
| Sector | IBB | IWM |
|---|---|---|
| Health Care | 91.0% | 16.6% |
| Industrials | 0.0% | 17.9% |
| Financials | 0.0% | 15.3% |
| Information Technology | 0.0% | 13.6% |
| Consumer Discretionary | 0.0% | 8.0% |
| Other Sectors | 0.0% | 22.7% |
| Unclassified | 8.9% | 5.5% |
Share of each fund's portfolio weight by GICS-style sector, compiled from issuer fund data and our own classification of the holdings, not the issuers' published sector charts. “Unclassified” is weight we could not classify (9% of IBB, 5% of IWM).
Performance
| Fund | 1M | YTD | 1Y | 3Y (ann.) | 5Y (ann.) | 10Y (ann.) | Yield |
|---|---|---|---|---|---|---|---|
| IBB | -0.3% | +17.3% | +51.0% | +16.4% | +3.1% | +7.4% | 0.21% |
| IWM | +1.8% | +23.0% | +38.6% | +17.1% | +7.5% | +10.8% | 0.88% |
Total returns including dividends, from adjusted daily closes as of 2026-08-07. 3Y/5Y/10Y are annualized. Yield is trailing-12-month distributions over the last close. Past performance does not predict future results.
Project the growth of $10,000 in IBB vs IWM →
Shared Holdings(172)
The top 10 shared positions account for 27% of the overlap, led by BBIO, MDGL and ARWR.
 BBIOBridgebio Pharma, Inc. | 1.13% | 0.40% | 0.40% |
|---|---|---|---|
 MDGLMadrigal Pharmaceuticals, Inc. | 1.00% | 0.30% | 0.30% |
 ARWRArrowhead Pharmaceuticals, Inc. | 0.75% | 0.29% | 0.29% |
 PRAXPraxis Precision Medicines, Inc. | 0.77% | 0.28% | 0.28% |
 CYTKCytokinetics, Inc. | 0.73% | 0.27% | 0.27% |
 PCVXVaxcyte, Inc. | 0.75% | 0.25% | 0.25% |
 AXSMAxsome Therapeutics, Inc. | 0.66% | 0.24% | 0.24% |
 KRYSKrystal Biotech, Inc. | 0.60% | 0.22% | 0.22% |
 PTGXProtagonist Therapeutics, Inc. | 0.58% | 0.21% | 0.21% |
 ALKSAlkermes plc | 0.53% | 0.20% | 0.20% |
 COGTCogent Biosciences, Inc. | 0.48% | 0.19% | 0.19% |
 PTCTPTC Therapeutics, Inc. | 0.50% | 0.18% | 0.18% |
| Nuvalent, Inc., Class A | 0.45% | 0.17% | 0.17% |
 430Terns Pharmaceuticals, Inc. | 0.46% | 0.17% | 0.17% |
 XENEXenon Pharmaceuticals, Inc. | 0.43% | 0.17% | 0.17% |
 KYMRKymera Therapeutics, Inc. | 0.53% | 0.16% | 0.16% |
 RYTMRhythm Pharmaceuticals, Inc. | 0.51% | 0.16% | 0.16% |
 ACLXArcellx, Inc. | 0.47% | 0.15% | 0.15% |
 1CGCRISPR Therapeutics AG | 0.39% | 0.15% | 0.15% |
 AM6Amicus Therapeutics, Inc. | 0.41% | 0.15% | 0.15% |
 SRRKScholar Rock Holding Corp. | 0.36% | 0.15% | 0.15% |
 CGONCG oncology, Inc. | 0.32% | 0.14% | 0.14% |
 MIRMMirum Pharmaceuticals, Inc. | 0.45% | 0.13% | 0.13% |
 APGEApogee Therapeutics, Inc. | 0.37% | 0.12% | 0.12% |
 CRNXCrinetics Pharmaceuticals, Inc. | 0.32% | 0.12% | 0.12% |
Frequently Asked Questions
How much do IBB and IWM overlap?
IBB and IWM overlap by 9.7% of portfolio weight. They share 172 holdings (IBB holds 254 positions and IWM holds 1941), based on each fund's latest SEC-reported holdings.
Is it redundant to own both IBB and IWM?
The two portfolios are 9.7% identical by weight. Owning both is not redundant. Most of each portfolio is distinct, so the funds can serve different roles.
What are the biggest shared holdings of IBB and IWM?
The largest positions held by both funds are BBIO, MDGL, ARWR, PRAX and CYTK. Together the top 10 shared positions account for 27% of the total overlap.
What does IBB own that IWM doesn't?
82 positions (72.8% of IBB) are unique to IBB, led by GILD, AMGN and VRTX. In the other direction, 1769 positions (90.0% of IWM) are unique to IWM.