IBB vs XBI overlap - what they share and where they differ
IBB and XBI share 41.1% 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.
IBB and XBI
41.1%
121 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
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 IBB 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 IBB side by side
IBBiShares Biotechnology ETF
234
stock positions reported to the SEC
24.6% of its weight is in 113 names XBI does not hold
XBIState Street(R) SPDR(R) S&P(R) Biotech ETF
149
stock positions reported to the SEC
15.0% of its weight is in 28 names IBB does not hold
Where each fund's weight sits
Largest sectors for both funds
The widest gap is Healthcare: IBB has 2.3 points more of it.
The figures side by side
| IBB | XBI | |
|---|---|---|
| Filing date | Jun 30, 2026 | Jun 30, 2026 |
| Stock positions reported | 234 | 149 |
| Weight of the ten largest | 44.8% | 13.3% |
| Largest position | VRTX 8.1% | APGE 1.5% |
| Held alone | 113 positions, 24.6% | 28 positions, 15.0% |
| Covered by stock positions | 100% | 100% |
Holdings they share
| Stock | In IBB | In XBI | Counted |
|---|---|---|---|
| MRNAModerna, Inc. | 1.98% | 1.41% | 1.41% |
| RVMDRevolution Medicines, Inc. | 2.78% | 1.20% | 1.20% |
| NTRANatera, Inc. | 2.89% | 1.16% | 1.16% |
| ROIVRoivant Sciences Ltd. | 1.43% | 1.16% | 1.16% |
| INSMInsmed, Inc. | 1.78% | 1.08% | 1.08% |
| VRTXVertex Pharmaceuticals, Inc. | 8.08% | 1.06% | 1.06% |
| BIIBBiogen, Inc. | 2.47% | 1.03% | 1.03% |
| INCYIncyte Corp. | 1.75% | 1.00% | 1.00% |
| IONSIonis Pharmaceuticals, Inc. | 1.00% | 1.00% | 1.00% |
| AMGNAmgen, Inc. | 7.83% | 0.99% | 0.99% |
What each holds alone
The heaviest positions one fund reports and the other does not.
Only in IBB
Only in XBI
Questions people ask
Is IBB the same as XBI?
41.1% of their weight sits in the same 121 holdings. IBB also reports ARGX, ILMN, ONC, which the other does not. XBI also reports VKTX, SLS, DNTH, which the other does not.
How is the overlap between IBB 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 IBB and 100% of XBI, so the number cannot exceed the smaller coverage.
Which holds more, XBI or IBB?
IBB reports 234 stock positions and XBI reports 149. 24.6% of IBB's weight sits in names XBI does not hold, and 15.0% of XBI's weight in names IBB does not hold. The ten largest positions are 44.8% of IBB and 13.3% of XBI.
How do IBB and XBI differ by sector?
The widest gap is Healthcare: IBB has 2.3 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.