Every large index ETF runs a second business that its fact sheet mentions in one line and never quantifies: it lends its shares out, mostly to people who want to sell them short, and takes collateral in return. The income is small and real. The counterparty exposure is neither disclosed on the fund page nor summarised by any data vendor.
It is, however, in the filing. Item B.4.a of Form N-PORT requires the fund to name every borrower, give its legal entity identifier, and state the aggregate value on loan to it. Read across the quarterly archive, that turns into something no fact sheet contains: a dated record of exactly which firms hold a fund's stock, and how that has changed.
For the iShares Russell 2000 ETF, it has changed a great deal, and quickly.
Data as of 2026-06-30 (filing period) · received by the SEC 2026-08-25 · analysis written 2026-09-25. The next filing will restate all of it, and this page will be re-measured when it arrives.
What IWM's filing says
At 30 June 2026 IWM held $83.0 billion of net assets and had $13.30 billion of stock out on loan — 16.03% of the fund — spread across 30 named borrowers. One of them, JP Morgan Securities LLC, held $10.94 billion of it: 82.3%. The next largest, BNP Paribas Prime Brokerage International, held 3.0%. The remaining 28 firms shared under 15% between them.
That is not how the fund's loan book looked two years ago, and the change did not happen in one step.
| Filing period | Borrowers | On loan | JP Morgan | Largest borrower's share | Lent, % of fund |
|---|---|---|---|---|---|
| 2024-09-30 | 30 | $7.37bn | $1.81bn | 24.6% | 10.6% |
| 2024-12-31 | 28 | $6.48bn | $1.69bn | 26.0% | 9.0% |
| 2025-03-31 | 31 | $6.02bn | $1.28bn | 21.3% | 9.4% |
| 2025-06-30 | 31 | $6.14bn | $2.14bn | 34.9% | 9.7% |
| 2025-09-30 | 31 | $11.05bn | $6.70bn | 60.6% | 15.6% |
| 2025-12-31 | 31 | $9.15bn | $6.02bn | 65.8% | 12.4% |
| 2026-03-31 | 31 | $10.12bn | $7.32bn | 72.3% | 14.1% |
| 2026-06-30 | 30 | $13.30bn | $10.94bn | 82.3% | 16.0% |
Two things move at once. The book roughly doubles, from $6.0 billion to $13.3 billion. And one borrower's share of it goes from a fifth to four fifths — JP Morgan's position grows 8.5-fold, from $1.28 billion to $10.94 billion, while the number of borrowers stays at about thirty. The other twenty-nine did not leave. They were simply outgrown.
Source: Form N-PORT for period 2026-06-30, accession 0002071691-26-019749. Every quarter, borrower by borrower: IWM.json.
Is that normal? Not for its siblings
The obvious first question is whether this is a BlackRock-wide change in how iShares funds lend. It is not. The same measure, for the other large iShares equity funds, over the same period:
| Fund | 2025-03 | 2025-06 | 2025-09 | 2025-12 | 2026-03 | 2026-06 |
|---|---|---|---|---|---|---|
| IWM (Russell 2000) | 21.3% | 34.9% | 60.6% | 65.8% | 72.3% | 82.3% |
| IJR (S&P 600 small-cap) | 22.9% | 21.2% | 19.1% | 17.1% | 16.8% | 15.4% |
| IJH (S&P 400 mid-cap) | 18.5% | 15.8% | 14.0% | 24.1% | 13.9% | 22.4% |
| IVV (S&P 500) | 20.8% | 31.7% | 34.4% | 18.9% | 33.4% | 24.7% |
| IWF (Russell 1000 Growth) | 22.7% | 28.8% | 21.8% | 21.8% | 21.4% | 41.4% |
| ITOT (total market) | 16.6% | 13.2% | 15.9% | 15.2% | 24.5% | 22.0% |
Every other fund bounces inside a band — the top borrower is somewhere between a seventh and two fifths of the book, and which firm holds that place changes from quarter to quarter. Only IWM climbs, and it climbs in a straight line for five consecutive filings. IJR, the other small-cap fund in the same family, moved the opposite way over exactly the same period.
Across the whole dataset, 82% is rare but not unique: of the 497 funds that name five or more borrowers, 102 have more than half their loan book with one firm, 51 have more than 60%, and 15 sit above 80%.
Concentration has house styles
The rare cases cluster in a way that is worth seeing. Among SPDR and related funds, one name keeps appearing at the top:
| Fund | Largest borrower's share | On loan | Borrowers | Largest borrower |
|---|---|---|---|---|
| XLB | 95.5% | $0.33bn | 5 | Barclays Bank PLC |
| XLV | 94.7% | $0.31bn | 8 | Barclays Bank PLC |
| XLF | 91.6% | $0.69bn | 9 | Barclays Bank PLC |
| SLYG | 78.8% | $0.76bn | 24 | Barclays Bank PLC |
| XAR | 70.7% | $0.80bn | 22 | Barclays Bank PLC |
| SLYV | 64.7% | $0.85bn | 23 | Barclays Bank PLC |
| SDY | 60.3% | $1.06bn | 24 | Barclays Bank PLC |
Seven funds from the same family, one counterparty dominating each. The amounts are an order of magnitude smaller than IWM's, which matters: $0.33 billion concentrated in one firm is a different proposition from $10.9 billion. But the pattern says something a single fund page cannot — that borrower concentration is often a property of the fund family and its lending arrangements, not of the individual fund.
The collateral question, answered honestly
The natural objection is that concentration does not matter because the loan is collateralised. That is mostly right, and the filing only half supports it.
IWM reported cash collateral worth 17.02% of net assets against a loan of 16.03% — 106.2% of the amount lent. Over the last six filings that figure has run between 100.2% and 110.6%, which is what a lender taking cash at a small margin looks like. On that evidence the loan is covered.
But that figure is a floor, not the whole collateral, and it is important not to oversell it. What appears in N-PORT is only collateral the fund holds as a position. Collateral taken in another form does not show up there at all. Across the 742 lending funds in this dataset, 337 report both a loan and cash collateral large enough to compare; their median cover is 102%, but 96 fall below 95% and 58 more funds lend materially while reporting almost no cash collateral. The filing does not say which explanation applies to which fund, so this site does not either. A fund below 100% here is not shown to be under-collateralised, and IWM at 106.2% is not shown to be fully collateralised — only that at least that much was held in cash.
What this does and does not tell you
It does not say why. The filing records the balance, not the reason. A single dominant borrower could reflect who is shorting the Russell 2000, or a change in how the lending programme allocates, or one very large borrow that happened to be open on 30 June. The filing distinguishes none of these, and neither will this page until something in the data does. This site has not measured short interest and does not assert a cause here.
It is a date, not a rate. Loans open and close daily. Every figure here is the balance on a quarter-end, which is the only day the fund is required to report.
It is not an allegation. Lending is disclosed, collateralised, and ordinary. What is unusual is the concentration and its direction of travel, and that is unusual enough to be worth a number.
It is not advice. Nothing here is a view on whether to hold IWM.
The data
Every figure above comes from Item B.4.a of the funds' own N-PORT filings, read across the whole archive: 742 lending funds, 116 borrowers named, $176 billion on loan at the latest filing of each. Before publication each borrower total is read a second time with a different parser and compared, and a mismatch stops the deploy.
- The dataset, with the borrower index in both directions: Who borrows the stock these funds lend
- IWM's own page, including its holdings and this section: /funds/iwm/
- Every quarter of IWM's loan book as JSON: /data/lending/IWM.json
- Free to reuse under CC BY 4.0, like everything else here.