Data as of Sep 12, 2026. Both funds on the fields they both publish, from the same sources.
IBB vs MDY: how they differ
IBB and MDY hold 4% of their weight in the same names, and IBB returned more over the year.
iShares Biotechnology ETF and SPDR S&P MidCap 400 ETF Trust.
What they hold in common
By the books each fund has filed, IBB and MDY hold 4% of their money in the same securities at the same weight.
| Holding | IBB | MDY |
|---|---|---|
| Illumina, Inc. | 2.07% | 0.73% |
| United Therapeutics Corp. | 1.74% | 0.64% |
| Neurocrine Biosciences, Inc. | 1.30% | 0.47% |
| Exelixis, Inc. | 1.03% | 0.38% |
| Medpace Holdings, Inc. | 0.95% | 0.33% |
| Cytokinetics, Inc. | 0.79% | 0.32% |
| Arrowhead Pharmaceuticals, Inc. | 0.84% | 0.32% |
| BioMarin Pharmaceutical, Inc. | 0.85% | 0.30% |
| Halozyme Therapeutics, Inc. | 0.72% | 0.26% |
| Repligen Corp. | 0.57% | 0.20% |
| Bruker Corp. | 0.52% | 0.18% |
| Only in IBB | Only in MDY |
|---|---|
| Vertex Pharmaceuticals, Inc. 8.09% | TWILIO INC 0.86% |
| Amgen, Inc. 7.84% | CARPENTER TECHNOLOGY CORP 0.85% |
| Gilead Sciences, Inc. 6.85% | MKS INC 0.83% |
| Regeneron Pharmaceuticals, Inc. 4.91% | CURTISS-WRIGHT CORP 0.77% |
| Argenx SE 3.76% | ENTEGRIS INC 0.76% |
| Alnylam Pharmaceuticals, Inc. 3.12% | NVENT ELECTRIC PLC 0.76% |
| Natera, Inc. 2.89% | ATI INC 0.74% |
| Revolution Medicines, Inc. 2.78% | TECHNIPFMC PLC 0.73% |
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.
| IBB iShares Biotechnology 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 | Biotechnology | S&P MidCap 400, book from IJH |
| Total return, 1 year | +41.5% | +13.0% |
| S&P 500 over the same days | +17.5% | +17.5% |
| Gap to the S&P 500 | +24.0 pts | −4.5 pts |
| Expense ratio | 0.44% | 0.23% |
| Already in the S&P 500 | 35.6% | 0.0% |
| Holdings | 248 | 400 |
IBB in plain words
IBB is an index equity fund tracking the Biotechnology. Over the year to Sep 11, 2026 it returned +41.5% with distributions reinvested, against +17.5% for the S&P 500 and +23.0% for the Nasdaq-100. The prospectus expense ratio is 0.44% a year. By its holdings filed for Jun 30, 2026, 36% of the fund by weight is stocks the S&P 500 also holds, across 248 positions, with the top ten at 44.8%. It sat 6.5% below its high of Aug 19, 2026 on Sep 11, 2026.
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, IBB or MDY?
- In the year to Sep 12, 2026, with distributions reinvested, IBB returned +41.5% and MDY returned +13.0%, so IBB returned more. One year is one year; the longer windows are in the table.
- Which is cheaper, IBB or MDY?
- IBB charges 0.44% a year and MDY charges 0.23%, so MDY is cheaper. Fees come from each fund's prospectus.
- How much do IBB and MDY overlap with the S&P 500?
- By their latest filed holdings, 36% of IBB 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.
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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, IBB against MDY, data as of Sep 12, 2026. https://etfiq.com/compare/any/IBB-MDY Free to use with attribution; the underlying files are at Open data.
A comparison is not a recommendation. Standards and sources