Overlap · from SEC filings
IEF vs SHY: what actually overlaps
IEF and SHY: 0.2% of a dollar ends up in the same companies either way (SEC Form N-PORT, 2026-05-31), across 1 securities the two funds both hold. Every free comparison tool can list the tickers in common; this weights them, which is the part that decides whether owning both changes anything.
The short version
Held alone, IEF behaves like 12.5 equally weighted positions and SHY like 83.2. Held together in equal size they behave like 43.3 — less diversified than holding SHY on its own — but not because the two funds overlap, since they share only 1 securities, 0.2% of a dollar by weight. Effective holdings weights by money, and half of it now sits in IEF, which behaves like 12.5 on its own. That is what pulls the blend down.
Overlap here is the sum, over securities both funds hold, of the smaller of the two weights: the share of a dollar that sits in the same company either way. Matching is on CUSIP. Figures are as of each fund's own reporting date (2026-05-31 and 2026-05-31), which do not always align.
Not 50/50, or holding a third fund alongside these two? The portfolio calculator runs this same math for any weights, across up to 12 funds.
Side by side
as filed| IEF | SHY | |
|---|---|---|
| Assets | $48B | $26B |
| Holdings | 16 | 90 |
| Effective holdings | 12.5 | 83.2 |
| Top ten weight | 85.53% | 16.11% |
| Largest position | 9.6% | 1.97% |
| Priced at market (Level 1) | 1.1% | 1.81% |
| Reporting date | 2026-05-31 | 2026-05-31 |
Where the overlap actually is
1The ten shared positions that account for the most of it, with what each fund holds of its own. Shared is the lesser of the two — the part that is held in common either way. Where the two columns diverge, one fund is making a larger bet on that company than the other, and holding both does not average it away.
| Company | IEF | SHY | Shared |
|---|---|---|---|
| BlackRock Funds III | 1.097% | 0.198% | 0.198% |
What the difference is made of
98.91% · 99.8%98.91% of IEF sits in companies SHY does not hold at all, and 99.8% of SHY in companies IEF does not hold. The largest of each, by weight in its own fund:
- United States of America
- United States of America
- United States of America
- United States of America
- United States of America
- United States of America
- United States of America
- United States of America
- United States of America
- United States of America
What each fund did last quarter
Each fund's newest filing against its previous one. A pair whose overlap is rising or falling does so because of these moves; the figures are the same ones on each fund's page and in its feed.
Written about this pair
1This page is the measurement. These essays argue about what it means, with the figures as they stood when each was written.
Related comparisons
2Other pairs involving IEF or SHY, ordered by how much they overlap.
| Pair | Overlap | Combined effective |
|---|---|---|
| IEF vs TLT | 1.06% | 35.6 |
| SHY vs TLT | 0.2% | 91 |
Sources and limits
Computed from SEC Form N-PORT (NPORT-P), the portfolio report every registered US fund files. Positions below 0.001% of net assets are dropped; weights are normalised to each filing's own total.
Unit investment trusts including SPY and DIA do not file N-PORT, so no overlap can be computed for them. Where a comparison is missing from this site, that is usually why rather than an oversight.
Overlap says what is held in common, not what will move together. Two funds with no shared holdings can still fall together, and the effective holding count takes no account of correlation. All 275 pairs are in the concentration dataset, and every fund's own history is on its fund page.