IWM vs XBI overlap - what they share and where they differ
IWM and XBI share 9.1% of their weight across 121 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.
IWM and XBI
9.1%
121 shared positions
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
XBI
State Street(R) SPDR(R) S&P(R) Biotech ETF
Reported positions cover 100% of the fund, 149 positions · Jun 30, 2026
Top 10: 13.3%·Holdings of XBI
Reported positions cover IWM 100%, XBI 100% of each fund. An overlap cannot exceed the smaller coverage, so a low figure can mean little overlap or thin reporting.
XBI vs IWM side by side
IWMiShares Russell 2000 ETF
1,785
stock positions reported to the SEC
90.7% of its weight is in 1,664 names XBI does not hold
XBIState Street(R) SPDR(R) S&P(R) Biotech ETF
149
stock positions reported to the SEC
28.2% of its weight is in 28 names IWM does not hold
Where each fund's weight sits
Largest sectors for both funds
The widest gap is Healthcare: XBI has 76.2 points more of it.
The figures side by side
| IWM | XBI | |
|---|---|---|
| Filing date | Jun 30, 2026 | Jun 30, 2026 |
| Stock positions reported | 1,785 | 149 |
| Weight of the ten largest | 3.4% | 13.3% |
| Largest position | MOG.A 0.4% | APGE 1.5% |
| Held alone | 1,664 positions, 90.7% | 28 positions, 28.2% |
| Covered by stock positions | 100% | 100% |
Holdings they share
| Stock | In IWM | In XBI | Counted |
|---|---|---|---|
| CYTKCytokinetics, Inc. | 0.35% | 1.18% | 0.35% |
| KRYSKrystal Biotech, Inc. | 0.30% | 1.10% | 0.30% |
| ALKSAlkermes plc | 0.27% | 1.11% | 0.27% |
| PRAXPraxis Precision Medicines, Inc. | 0.26% | 1.29% | 0.26% |
| TGTXTG Therapeutics, Inc. | 0.25% | 1.09% | 0.25% |
| PCVXVaxcyte, Inc. | 0.24% | 1.19% | 0.24% |
| PTGXProtagonist Therapeutics, Inc. | 0.23% | 1.07% | 0.23% |
| KYMRKymera Therapeutics, Inc. | 0.22% | 1.36% | 0.22% |
| PTCTPTC Therapeutics, Inc. | 0.21% | 1.03% | 0.21% |
| COGTCogent Biosciences, Inc. | 0.20% | 1.14% | 0.20% |
What each holds alone
The heaviest positions one fund reports and the other does not.
Only in IWM
Only in XBI
Questions people ask
Is IWM the same as XBI?
9.1% of their weight sits in the same 121 holdings. IWM also reports MOG.A, HUT, BTSG, which the other does not. XBI also reports MRNA, VKTX, RVMD, which the other does not.
How is the overlap between IWM and XBI 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 IWM and 100% of XBI, so the number cannot exceed the smaller coverage.
Which holds more, XBI or IWM?
IWM reports 1,785 stock positions and XBI reports 149. 90.7% of IWM's weight sits in names XBI does not hold, and 28.2% of XBI's weight in names IWM does not hold. The ten largest positions are 3.4% of IWM and 13.3% of XBI.
How do IWM and XBI differ by sector?
The widest gap is Healthcare: XBI has 76.2 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.
Add a third fund in the tool·All fund pairs
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.