The takeaway
Alnylam Pharmaceuticals Inc shows a pronounced seasonal pattern over 10 years of data — strongest in June (+11.5%) and softest in October (−8.7%).
Right now
In July, the stock has risen 60% of years, averaging +3.8%, about +1.7 pts better than the S&P 500.
The full picture
Alnylam Pharmaceuticals Inc's most dependable month has been June, higher in 8 of 10 years; October has been its least reliable, up just 20% of the time.
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Month by month
The stock's clearest edge over the S&P 500 lands in June (+11.3 pts); it has trailed the market most in October (−9.7 pts).
“vs S&P” is Alnylam Pharmaceuticals Inc’s average for a month minus the S&P 500’s average for that same month — isolating Alnylam Pharmaceuticals Inc’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, June has closed higher 100% of the time versus 80% across the last 10 years — the pattern is strengthening.
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
The seasonal story is really one month's story — June. It has closed higher in 8 of 10 Junes, a concentration the rest of the calendar can't touch.
The strength looks broad-based rather than freakish: its average (+11.5%) and median (+9.7%) sit close together, so no single blow-out year is flattering the figure. That reliability comes with real swings, mind — even June ranges by 20.0% from year to year, so any single year can land far from the average. Better still, that strength is the stock's own and not just a buoyant market — June has outpaced the S&P 500 by +11.3 points on average. Few peers keep such company in June — the typical stock clears it just 52% of the time.
June anchors a run, too: the May-through-August window has been the stock's reliable season. The weaker half of the year is plainer: October has been the soft spot — the weakest of 4 months that average a loss (−8.7%), and the edge isn't year-round — the stock has trailed the S&P 500 in October, December, and February. Its roughest month on record was a −47.8% October in 2016 — a reminder of how hard even a seasonal name can fall.
June has now closed higher 7 years running. If anything it has sharpened recently — the last five Junes run ahead of the earlier years.
For a stock this dependable in June, the sharper question is the rest of the year — outside its strong stretch, the calendar gives far less to lean on. With returns that swing hard year to year, the signal is best held loosely.
Short answers on the stock's best month (June), its worst (October), and whether it really trades seasonally.
Yes, to a pronounced degree. Since 2016 its best month (June, +11.5%) has run well ahead of its worst (October, −8.7%) — the heatmap above shows how steady that gap has been year to year.
June has been the strongest, averaging +11.5% and closing higher in 8 of 10 years since 2016.
It's the weakest, averaging −8.7% — 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.
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