The takeaway
iShares Biotechnology ETF shows a moderate seasonal pattern over 10 years of data — strongest in June (+2.3%) and softest in March (−2.4%).
Right now
In July, the fund has risen 80% of years, averaging +3.0%, about +0.8 pts better than the S&P 500.
The full picture
iShares Biotechnology ETF's most dependable month has been June, higher in 9 of 10 years; March has been its least reliable, up just 20% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Win rate % | ||||||||||||
| Median return % | ||||||||||||
| 2025 | ||||||||||||
| 2024 | ||||||||||||
| 2023 | ||||||||||||
| 2022 | ||||||||||||
| 2021 | ||||||||||||
| 2020 | ||||||||||||
| 2019 | ||||||||||||
| 2018 | ||||||||||||
| 2017 | ||||||||||||
| 2016 |
Month by month
The fund's clearest edge over the S&P 500 lands in June (+2.0 pts); it has trailed the market most in March (−3.4 pts).
“vs S&P” is iShares Biotechnology ETF’s average for a month minus the S&P 500’s average for that same month — isolating iShares Biotechnology ETF’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, June has closed higher 100% of the time versus 90% across the last 10 years — the pattern is holding.
Figures are the typical (median) June return and how often it rose — the last 5 years versus the last 10(the heatmap’s default window). This verdict stays anchored to that 10-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
Strip the year back and a single month does the heavy lifting: June, up in 9 of 10 Junes while the other eleven tend to blur together.
Its average (+2.3%) and median (+2.0%) land within a hair of each other — the tell of steady, year-after-year gains rather than one outlier doing the work. Crucially, the gain is the fund's own rather than a rising tide's: June has cleared the S&P 500 by +2.0 points above the index. That consistency sets it apart from the field, where the average stock manages June only about 52% of the time.
The strength clusters rather than stands alone — June–August forms a firm stretch that carries much of the year. At the other end of the calendar, March has been the soft spot — the weakest of 5 months that average a loss (−2.4%), and the edge isn't year-round — the fund has trailed the S&P 500 in March, October, and February. Its roughest month on record was a −18.3% January in 2016 — a reminder of how hard even a seasonal name can fall.
June has now closed higher 9 years running. Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
The takeaway is less about when to buy than what to expect: June aside, the fund's months offer little reliable tilt.
Short answers on the fund's best month (June), its worst (March), and whether it really trades seasonally.
Yes, to a moderate degree. Since 2016 its best month (June, +2.3%) has run well ahead of its worst (March, −2.4%) — the heatmap above shows how steady that gap has been year to year.
June has been the strongest, averaging +2.3% and closing higher in 9 of 10 years since 2016.
It's the weakest, averaging −2.4% — historically a soft spot, though it still varies from year to year.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade