Correlation Analysis
Biogen Inc. Common Stock vs BERKSHIRE HATHAWAY Class B
BIIB vs BRK.B
-0.802
Strong inverse
When one moves up, the other tends to move down.
Biogen Inc. Common Stock
↗BIIB
Biogen is an established biopharmaceutical company focused on treatments for neurodegenerative and rare diseases. Its declining multiple sclerosis franchise is its largest revenue generator and contributed 40% of total revenue in 2025. Biogen also generates significant revenue from its CD20 collaboration agreements with Roche (19% of total in 2025), which includes oncology drugs Rituxan and Gazyva and multiple sclerosis drug Ocrevus. Biogen's newer franchises include Spinraza (spinal muscular atrophy, with partner Ionis), Leqembi (Alzheimer's disease, collabroation revenue from its partner Eisai), Skyclarys (Friedreich's ataxia, Reata), Zurzuvae (postpartum depression, Sage), and Qalsody (amyotrophic lateral sclerosis, Ionis).
Market cap 25.3B · 7,500 employees
BERKSHIRE HATHAWAY Class B
↗BRK.B
Berkshire Hathaway is a holding company with a wide array of subsidiaries engaged in diverse activities. The firm's core business segment is insurance, run primarily through Geico, Berkshire Hathaway Reinsurance Group, and Berkshire Hathaway Primary Group. Berkshire has used the excess cash thrown off from its operations to acquire Burlington Northern Santa Fe (railroad), Berkshire Hathaway Energy (utilities and energy distributors), and the companies that make up its manufacturing, service, and retailing operations (which include Precision Castparts, Lubrizol, Clayton Homes, Marmon, and IMC/ISCAR). The conglomerate is unique in that it is run on a completely decentralized basis. Berkshire is expected to generate close to $375 billion in revenue in 2025.
Market cap 1T
Time Series
Relative Performance
Who Moves First
BRK.B leads BIIB by 6 days
BRK.B tends to move before BIIB.
After testing 13 timing shifts, the strongest relationship was -0.808 (they moved in opposite directions).
Do They Crash Together?
Correlation by Market Regime
How these series behave when markets are rising, falling, or diverging. A correlation that holds in drawdowns is very different from one that only works in rallies.
Both Rising
+0.039
10 periods · Return correlation when both series rose
Both Falling
-0.523
8 periods · Return correlation when both series fell
Diverging
-0.605
17 periods · Return correlation when series moved apart
R-Squared
64.3%
Share of variance in one series explained by the other.
Trend Agreement
58.8%
How often both series moved in the same direction period-to-period.
Overlap Quality
1,253
Deep shared window — 1,253 usable pairs.
Significance
p < 0.001
95% CI: [-0.821, -0.781]
Scatter
XY Regression
Pipeline
Data quality details
Pipeline
Data quality details
Pipeline Summary
1,253 paired data points survived the daily window.
Raw input
1,253
1,254
Normalized
1,253
1,254
Prepared
1,253
1,254
Aligned
1,253
1,253
Invalid removed
0
A: 0 / B: 0
Duplicates removed
0
A: 0 / B: 0
Alignment drops
1
A: 0 / B: 1
Series A
Biogen Inc. Common Stock
BIIB
Market cap 25.3B · 7,500 employees
Stock · 1,253 raw → 1,253 prepared
Series B
BERKSHIRE HATHAWAY Class B
BRK.B
Market cap 1T
Stock · 1,254 raw → 1,254 prepared
Sign agreement
100.0%
How often both values share the same sign.
Zero crossings
3
Estimated crossover points between normalized spreads.
Slope
-1.1293
Linear regression slope.
Intercept
631.6559
Linear regression intercept.
Related Extremes
Highest and Lowest Correlated
Saved 7 hours ago · ID: stock-biib-vs-stock-brk-b-daily