IBB vs IWM overlap - what they share and where they differ
IBB and IWM share 10.4% of their weight across 163 common positions, read from what each fund reported to the SEC.
Each week Ploutos reads the reported positions of the largest US equity ETFs and measures, pair by pair, the weight they share: for every stock both funds hold, the smaller of the two weights counts. Two funds tracking the same index land near 100%. A sector fund inside a broad index fund lands at roughly that sector's weight.
IBB and IWM
10.4%
163 shared positions
IBB
iShares Biotechnology ETF
Reported positions cover 100% of the fund, 234 positions · Jun 30, 2026
Top 10: 44.8%·Holdings of IBB
IWM
iShares Russell 2000 ETF
Reported positions cover 100% of the fund, 1,785 positions · Jun 30, 2026
Top 10: 3.4%·Holdings of IWM
Reported positions cover IBB 100%, IWM 100% of each fund. An overlap cannot exceed the smaller coverage, so a low figure can mean little overlap or thin reporting.
IWM vs IBB side by side
IBBiShares Biotechnology ETF
234
stock positions reported to the SEC
74.2% of its weight is in 71 names IWM does not hold
IWMiShares Russell 2000 ETF
1,785
stock positions reported to the SEC
89.4% of its weight is in 1,622 names IBB does not hold
Where each fund's weight sits
Largest sectors for both funds
The widest gap is Healthcare: IBB has 78.5 points more of it.
The figures side by side
| IBB | IWM | |
|---|---|---|
| Filing date | Jun 30, 2026 | Jun 30, 2026 |
| Stock positions reported | 234 | 1,785 |
| Weight of the ten largest | 44.8% | 3.4% |
| Largest position | VRTX 8.1% | MOG.A 0.4% |
| Held alone | 71 positions, 74.2% | 1,622 positions, 89.4% |
| Covered by stock positions | 100% | 100% |
Holdings they share
| Stock | In IBB | In IWM | Counted |
|---|---|---|---|
| CYTKCytokinetics, Inc. | 0.79% | 0.35% | 0.35% |
| KRYSKrystal Biotech, Inc. | 0.75% | 0.30% | 0.30% |
| ALKSAlkermes plc | 0.67% | 0.27% | 0.27% |
| PRAXPraxis Precision Medicines, Inc. | 0.68% | 0.26% | 0.26% |
| PCVXVaxcyte, Inc. | 0.64% | 0.24% | 0.24% |
| PTGXProtagonist Therapeutics, Inc. | 0.58% | 0.23% | 0.23% |
| KYMRKymera Therapeutics, Inc. | 0.64% | 0.22% | 0.22% |
| NUVALENT, INC. | 0.50% | 0.21% | 0.21% |
| PTCTPTC Therapeutics, Inc. | 0.51% | 0.21% | 0.21% |
| COGTCogent Biosciences, Inc. | 0.44% | 0.20% | 0.20% |
What each holds alone
The heaviest positions one fund reports and the other does not.
Only in IBB
Only in IWM
Questions people ask
Is IBB the same as IWM?
10.4% of their weight sits in the same 163 holdings. IBB also reports VRTX, AMGN, GILD, which the other does not. IWM also reports MOG.A, HUT, BTSG, which the other does not.
How is the overlap between IBB and IWM measured?
For every stock both funds report, the smaller of the two weights counts, and the sum is the overlap. The reported positions cover 100% of IBB and 100% of IWM, so the number cannot exceed the smaller coverage.
Which holds more, IWM or IBB?
IBB reports 234 stock positions and IWM reports 1,785. 74.2% of IBB's weight sits in names IWM does not hold, and 89.4% of IWM's weight in names IBB does not hold. The ten largest positions are 44.8% of IBB and 3.4% of IWM.
How do IBB and IWM differ by sector?
The widest gap is Healthcare: IBB has 78.5 points more of it. Sectors come from each holding's SIC code in its SEC record, summed by the weight the fund reports.
Where do the numbers come from?
From each fund's own N-PORT filing to the SEC, which lists every position and its weight. The comparison uses every equity position the fund reports; cash, futures and bonds are not counted, which is why a coverage figure sits next to every result. Holdings change between filings.
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Descriptive data from public SEC filings. Nothing on this page is a recommendation to buy, sell or hold any fund or stock, and holdings change between filings.