IBB vs MDYG: Holdings Overlap
iShares · 254 holdings · $9.3B · as of 2026-03-31
MDYGState Street® SPDR® S&P 400™ Mid Cap Growth ETF
State Street (SPDR) · 245 holdings · $2.9B · as of 2026-08-06
Holdings snapshots are 128 days apart (IBB: 2026-03-31, MDYG: 2026-08-06). Weights and index membership change between snapshots, so the true current overlap is typically higher than shown. For funds tracking the same index, the gap can be 5–15 points.
How similar are IBB and MDYG?
iShares Biotechnology ETF (IBB, by iShares) holds 254 positions; State Street® SPDR® S&P 400™ Mid Cap Growth ETF (MDYG, by State Street (SPDR)) holds 245. They have 13 holdings in common, and by portfolio weight the two funds are 7.5% identical. In practical terms the pair is lightly overlapping, with most of each portfolio distinct.
- Overlap by Weight
- 7.5%Sum of the smaller weight of each shared holding
- Shared Holdings
- 13IBB holds 254 · MDYG holds 245
- Weight in Shared Holdings
- IBB 13%·MDYG 8%Share of each fund's weight in stocks both funds own
Based on each fund's latest official holdings. How is this calculated?
What makes each fund different
Only in IBB
241 of 254 positions (86.8% of the fund) are not held by MDYG. Showing the top 30 by weight.
Sector Breakdown
| Sector | IBB | MDYG |
|---|---|---|
| Health Care | 91.0% | 15.5% |
| Industrials | 0.0% | 29.8% |
| Information Technology | 0.0% | 20.2% |
| Consumer Discretionary | 0.0% | 9.0% |
| Financials | 0.0% | 8.0% |
| Other Sectors | 0.0% | 17.3% |
| Unclassified | 8.9% | 0.0% |
Share of each fund's portfolio weight by GICS-style sector, compiled from issuer fund data and our own classification of the holdings, not the issuers' published sector charts. “Unclassified” is weight we could not classify (9% of IBB, 0% of MDYG).
Performance
| Fund | 1M | YTD | 1Y | 3Y (ann.) | 5Y (ann.) | 10Y (ann.) | Yield |
|---|---|---|---|---|---|---|---|
| IBB | -0.3% | +17.3% | +51.0% | +16.4% | +3.1% | +7.4% | 0.21% |
| MDYG | +3.3% | +21.6% | +28.0% | +16.0% | +8.5% | +11.3% | 0.56% |
Total returns including dividends, from adjusted daily closes as of 2026-08-07. 3Y/5Y/10Y are annualized. Yield is trailing-12-month distributions over the last close. Past performance does not predict future results.
Project the growth of $10,000 in IBB vs MDYG →
Shared Holdings(13)
The top 10 shared positions account for 90% of the overlap, led by UTHR, NBIX and ILMN.
 UTHRUnited Therapeutics Corporation COM | 2.30% | 1.21% | 1.21% |
|---|---|---|---|
 NBIXNeurocrine Biosciences Inc COM | 1.18% | 0.86% | 0.86% |
 ILMNIllumina Inc COM | 1.68% | 0.84% | 0.84% |
 MEDPMedpace Holdings Inc. COM | 1.00% | 0.70% | 0.70% |
 EXELExelixis, Inc. COM | 0.99% | 0.70% | 0.70% |
 ARWRArrowhead Pharmaceuticals Inc COM | 0.75% | 0.64% | 0.64% |
 HALOHalozyme Therapeutics Inc COM | 0.69% | 0.54% | 0.54% |
 ROIVRoivant Sciences Ltd SHS | 1.24% | 0.49% | 0.49% |
 KRYSKrystal Biotech Inc COM | 0.60% | 0.45% | 0.45% |
 BMRNBiomarin Pharmaceutical Inc. COM | 0.98% | 0.36% | 0.36% |
 CYTKCytokinetics Incorporated | 0.73% | 0.32% | 0.32% |
 RGENRepligen Corporation COM | 0.58% | 0.25% | 0.25% |
 BRKRBruker Corporation COM | 0.34% | 0.16% | 0.16% |
Frequently Asked Questions
How much do IBB and MDYG overlap?
IBB and MDYG overlap by 7.5% of portfolio weight. They share 13 holdings (IBB holds 254 positions and MDYG holds 245), based on each fund's latest SEC-reported holdings.
Is it redundant to own both IBB and MDYG?
The two portfolios are 7.5% identical by weight. Owning both is not redundant. Most of each portfolio is distinct, so the funds can serve different roles.
What are the biggest shared holdings of IBB and MDYG?
The largest positions held by both funds are UTHR, NBIX, ILMN, MEDP and EXEL. Together the top 10 shared positions account for 90% of the total overlap.
What does IBB own that MDYG doesn't?
241 positions (86.8% of IBB) are unique to IBB, led by GILD, AMGN and VRTX. In the other direction, 232 positions (92.3% of MDYG) are unique to MDYG.