Seasonality
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BIIB - Average returns for the respective month in the last 5 years
BIIB - Average growth of $100 invested at start of year
5 years of data
Jun is the seasonally strongest month over 5Y.
Jun averages +3.5% with a 57% win rate across 5 years of history.
Oct shows persistent seasonal weakness.
Oct averages -3.1% with only a 33% win rate across 5 years of history.
Q2 (Apr–May–Jun) is the seasonally strongest quarter.
The three months of Q2 combine for a +3.7% average return historically.
Q1 historically shows a slow seasonal start.
Q1 (Jan–Mar) averages -0.4% historically, with January alone posting a 50% win rate.
2026 YTD is tracking above the 5Y seasonal average.
At day 155 of the year, the current YTD return is +20.9% vs the historical average for the same point.
Monthly Returns Heatmap
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026 | 2.22% | 6.63% | -4.43% | 3.25% | 3.55% | 10.23% | -6.07% | 3.39% | ||||
| 2025 | -5.88% | -2.38% | -2.60% | -11.52% | 7.19% | -3.24% | 1.92% | 3.30% | 5.94% | 10.13% | 18.03% | -3.35% |
| 2024 | -4.68% | -12.03% | -0.63% | -0.38% | 4.71% | 3.06% | -8.03% | -3.96% | -5.33% | -10.24% | -7.68% | -4.80% |
| 2023 | 5.05% | -7.23% | 3.03% | 9.42% | -2.57% | -3.90% | -5.15% | -1.05% | -3.87% | -7.58% | -1.46% | 10.55% |
| 2022 | -5.80% | -6.63% | -0.19% | -1.50% | -3.59% | 1.97% | 5.45% | -9.15% | 36.66% | 6.16% | 7.67% | -9.26% |
| 2021 | 15.42% | -3.44% | 2.52% | -4.44% | 0.06% | 29.46% | -5.64% | 3.73% | -16.50% | -5.76% | -11.60% | 1.77% |
| 2020 | 14.71% | 2.59% | -6.18% | 3.46% | -12.88% | 2.67% | 4.71% | -1.38% | -11.14% | -4.72% | 1.95% | |
| Avg | 1.05% | -1.48% | 0.04% | -1.62% | 1.83% | 3.53% | -2.12% | -0.40% | 2.59% | -3.07% | 0.04% | -0.52% |
BIIB Distribution of Daily Returns from 2021 to 2026
BIIB Distribution of Daily % Changes