IBB vs SPY: Holdings Overlap
iShares · 254 holdings · $9.3B · as of 2026-03-31
SPYState Street® SPDR® S&P 500® ETF Trust
State Street (SPDR) · 504 holdings · $812.0B · as of 2026-08-06
Holdings snapshots are 128 days apart (IBB: 2026-03-31, SPY: 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 SPY?
iShares Biotechnology ETF (IBB, by iShares) holds 254 positions; State Street® SPDR® S&P 500® ETF Trust (SPY, by State Street (SPDR)) holds 504. They have 9 holdings in common, and by portfolio weight the two funds are 1.0% identical. In practical terms the pair is essentially distinct, holding almost none of the same securities.
- Overlap by Weight
- 1.0%Sum of the smaller weight of each shared holding
- Shared Holdings
- 9IBB holds 254 · SPY holds 504
- Weight in Shared Holdings
- IBB 37%·SPY 1%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
245 of 254 positions (62.6% of the fund) are not held by SPY. Showing the top 30 by weight.
Sector Breakdown
| Sector | IBB | SPY |
|---|---|---|
| Health Care | 91.0% | 8.9% |
| Information Technology | 0.0% | 37.6% |
| Financials | 0.0% | 12.3% |
| Communication Services | 0.0% | 9.7% |
| Consumer Discretionary | 0.0% | 9.3% |
| Other Sectors | 0.0% | 22.1% |
| 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 SPY).
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% |
| SPY | +3.4% | +14.0% | +23.7% | +21.2% | +13.3% | +15.3% | 0.97% |
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 SPY →
Shared Holdings(9)
The top 9 shared positions account for 100% of the overlap, led by AMGN, GILD and VRTX.
 AMGNAmgen Inc. COM | 7.51% | 0.33% | 0.33% |
|---|---|---|---|
 GILDGilead Sciences Inc. COM | 7.75% | 0.24% | 0.24% |
 VRTXVertex Pharmaceuticals Incorporated COM | 7.44% | 0.19% | 0.19% |
 REGNRegeneron Pharmaceuticals, Inc. COM | 7.21% | 0.12% | 0.12% |
 BIIBBiogen Inc COM | 2.46% | 0.05% | 0.05% |
 INCYIncyte Corporation. COM | 1.70% | 0.03% | 0.03% |
 MRNAModerna Inc COM | 1.68% | 0.03% | 0.03% |
 CRLCharles River Laboratories International, Inc. COM | 0.77% | 0.02% | 0.02% |
 TECHBio-Techne Corp COM | 0.74% | 0.02% | 0.02% |
Frequently Asked Questions
How much do IBB and SPY overlap?
IBB and SPY overlap by 1.0% of portfolio weight. They share 9 holdings (IBB holds 254 positions and SPY holds 504), based on each fund's latest SEC-reported holdings.
Is it redundant to own both IBB and SPY?
The two portfolios are 1.0% identical by weight. Owning both is genuine diversification: the funds hold almost none of the same securities.
What are the biggest shared holdings of IBB and SPY?
The largest positions held by both funds are AMGN, GILD, VRTX, REGN and BIIB. Together the top 9 shared positions account for 100% of the total overlap.
What does IBB own that SPY doesn't?
245 positions (62.6% of IBB) are unique to IBB, led by ALNY, INSM and ARGX. In the other direction, 495 positions (98.9% of SPY) are unique to SPY.