IWM vs XBI: how much do they overlap?
iShares Russell 2000 ETF (IWM) · SPDR S&P Biotech ETF (XBI)
overlap by weight · 109 shared holdings
IWM: 1934 holdings (as of 2026-03-31) · XBI: 149 holdings (as of 09-Jul-2026)
Note: the two funds' latest official filings have different dates, which can understate overlap slightly for funds tracking similar indexes.
Low overlap
What this means
IWM and XBI hold mostly different stocks. Combining them genuinely spreads your exposure across different parts of the market.
Overlap by weight sums the smaller of the two funds' weights for every stock they both hold — it answers "how much of my money is in the same stocks either way?" See methodology.
Top shared holdings
| Company | Ticker | in IWM | in XBI |
|---|---|---|---|
| Bridgebio Pharma, Inc. | BBIO | 0.4% | 1.2% |
| Madrigal Pharmaceuticals, Inc. | MDGL | 0.3% | 1.06% |
| Arrowhead Pharmaceuticals, Inc. | ARWR | 0.29% | 1.06% |
| Praxis Precision Medicines, Inc. | PRAX | 0.28% | 1.24% |
| Cytokinetics, Inc. | CYTK | 0.27% | 1.15% |
| Vaxcyte, Inc. | PCVX | 0.25% | 1.18% |
| Krystal Biotech, Inc. | KRYS | 0.22% | 1.06% |
| Protagonist Therapeutics, Inc. | PTGX | 0.21% | 1.16% |
| Alkermes plc | ALKS | 0.2% | 1.1% |
| Cogent Biosciences, Inc. | COGT | 0.19% | 1.15% |
FAQ
How much do IWM and XBI overlap?
IWM and XBI have a 8% overlap by weight, sharing 109 holdings (out of 1934 in IWM and 149 in XBI), based on official issuer holdings as of 2026-03-31.
What does 8% overlap mean?
IWM and XBI hold mostly different stocks. Combining them genuinely spreads your exposure across different parts of the market.
Which stocks do IWM and XBI both hold?
The largest shared positions are Bridgebio Pharma, Inc., Madrigal Pharmaceuticals, Inc., Arrowhead Pharmaceuticals, Inc., Praxis Precision Medicines, Inc., Cytokinetics, Inc.. The full list of top shared holdings with weights in each fund is shown on this page.