Data as of Sep 12, 2026. Both funds on the fields they both publish, from the same sources.
IWB vs MDY: how they differ
IWB and MDY hold 4% of their weight in the same names, and IWB returned more over the year.
iShares Russell 1000 ETF and SPDR S&P MidCap 400 ETF Trust.
What they hold in common
By the books each fund has filed, IWB and MDY hold 4% of their money in the same securities at the same weight.
| Holding | IWB | MDY |
|---|---|---|
| TWILIO INC. | 0.04% | 0.86% |
| CARPENTER TECHNOLOGY CORPORATION | 0.04% | 0.85% |
| MKS, INCORPORATED. | 0.04% | 0.83% |
| CURTISS-WRIGHT CORPORATION | 0.04% | 0.77% |
| ATI INC | 0.04% | 0.74% |
| ENTEGRIS, INC. | 0.04% | 0.76% |
| ILLUMINA, INC. | 0.04% | 0.73% |
| MACOM TECHNOLOGY SOLUTIONS HOLDINGS, INC | 0.04% | 0.69% |
| MASTEC, INC. | 0.04% | 0.71% |
| WOODWARD, INC. | 0.04% | 0.70% |
| Everpure, Inc | 0.04% | 0.69% |
| STERLING INFRASTRUCTURE, INC. | 0.04% | 0.71% |
| Only in IWB | Only in MDY |
|---|---|
| NVIDIA CORPORATION 6.73% | NVENT ELECTRIC PLC 0.76% |
| APPLE INC. 6.03% | TECHNIPFMC PLC 0.73% |
| MICROSOFT CORPORATION 4.00% | FABRINET 0.56% |
| AMAZON.COM, INC. 3.33% | ROIVANT SCIENCES LTD 0.44% |
| ALPHABET INC. 3.00% | JAZZ PHARMACEUTICALS PLC 0.42% |
| BROADCOM INC. 2.54% | RENAISSANCERE HOLDINGS LTD 0.37% |
| ALPHABET INC. 2.42% | MOOG INC 0.33% |
| MICRON TECHNOLOGY, INC. 1.88% | CYTOKINETICS INC 0.32% |
Weight overlap is an ETFIQ calculation: for every security both funds hold, the smaller of the two weights, summed. Above 50%, holding both is close to holding one of them twice. Holdings dated Jun 30, 2026.
| IWB iShares Russell 1000 ETF | MDY SPDR S&P MidCap 400 ETF Trust | |
|---|---|---|
| Where it sits | Core index fund | Core index fund |
| Issuer | iShares | State Street |
| What it is | Russell 1000 | S&P MidCap 400, book from IJH |
| Total return, 1 year | +16.7% | +13.0% |
| S&P 500 over the same days | +17.5% | +17.5% |
| Gap to the S&P 500 | −0.8 pts | −4.5 pts |
| Expense ratio | 0.15% | 0.23% |
| Already in the S&P 500 | 91.9% | 0.0% |
| Holdings | 1024 | 400 |
IWB in plain words
IWB is an index equity fund tracking the Russell 1000. Over the year to Sep 11, 2026 it returned +16.7% with distributions reinvested, against +17.5% for the S&P 500 and +23.0% for the Nasdaq-100. The prospectus expense ratio is 0.15% a year. By its holdings filed for Jun 30, 2026, 92% of the fund by weight is stocks the S&P 500 also holds, across 1024 positions, with the top ten at 33.5%.
MDY in plain words
MDY is an index equity fund tracking the S&P MidCap 400. Over the year to Sep 11, 2026 it returned +13.0% with distributions reinvested, against +17.5% for the S&P 500 and +23.0% for the Nasdaq-100. The prospectus expense ratio is 0.23% a year. By its holdings filed for Jun 30, 2026, 0% of the fund by weight is stocks the S&P 500 also holds, across 400 positions, with the top ten at 7.7%. It sat 5.3% below its high of Aug 14, 2026 on Sep 11, 2026.
Questions people ask
- Which returned more over the last year, IWB or MDY?
- In the year to Sep 12, 2026, with distributions reinvested, IWB returned +16.7% and MDY returned +13.0%, so IWB returned more. One year is one year; the longer windows are in the table.
- Which is cheaper, IWB or MDY?
- IWB charges 0.15% a year and MDY charges 0.23%, so IWB is cheaper. Fees come from each fund's prospectus.
- How much do IWB and MDY overlap with the S&P 500?
- By their latest filed holdings, 92% of IWB and 0% of MDY by weight is stocks the S&P 500 already holds. Between the two funds, 4% of their books are the same securities at the same weight.
Other comparisons
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Where these figures came from
ETFIQ links to the documents behind every figure. It is not affiliated with any issuer, and a link is not an endorsement.
Cite this page. ETFIQ, IWB against MDY, data as of Sep 12, 2026. https://etfiq.com/compare/any/IWB-MDY Free to use with attribution; the underlying files are at Open data.
A comparison is not a recommendation. Standards and sources