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At close · Thu, Jul 16, 2026
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HomeETFs & FundsETFsIBB’s top holdings drive nearly half of its biotech ET…

IBB’s top holdings drive nearly half of its biotech ETF assets

The iShares Biotechnology ETF holds 249 stocks, but its 10 largest positions account for 44% of assets, making performance more concentrated than the headline number suggests.

Yahoo Finance highlights that the iShares Biotechnology ETF (IBB) lists 249 stocks, yet its weighting means it tends to behave like roughly 35 equally weighted holdings. While IBB is designed to track an index of U.S. biotechnology companies, the article notes that concentration can dominate day to day moves. The fund’s ten largest holdings represent 44% of total assets. The largest single position is Vertex Pharmaceuticals at 7.8% of the fund, followed by Amgen at 7.6% and Gilead Sciences at 7.0%. With the top three companies together taking a large share of the portfolio, the performance of a small group can noticeably influence the ETF. Under the fund’s broad Health Care label, the article says the exposure is heavily tilted toward a single sub-industry. Biotechnology makes up 87% of assets, with Life Sciences Tools & Services the next largest at 9.2%, together accounting for the vast majority of what investors own.

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