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Correlation
of % moves
+47%
In sync
of periods
66%
History
daysdays · through 2026-05-22
1,254
These move in the same direction about 66% of the time
Their swing sizes loosely line up (~22% of the pattern is shared).
Strong enough to use as a signal — check the stability and regime notes below before relying on it.
Both lines start at the same point — easy to compare when growth rates are similar.
What to Watch
Holds in both up and down markets
The relationship is similar whether prices are rising or falling — reliable in both directions.
Rock solid
The relationship barely changes from period to period — treat it as a reliable signal.
Advanced
Statistics
In sync(i)
65.5%
Headline metric
Movement correlation(i)
+47%
Based on % moves
95% CI
+42% → +51%
Likely range of correlation
Pipeline
Pipeline Summary
1,254 paired data points survived the daily window.
Raw input
1,254
1,254
Normalized
1,254
1,254
Prepared
1,254
1,254
Aligned
1,254
1,254
Invalid removed
R²(i)
21.7%
Variance explained
Significance
p < 0.001
Statistical confidence
Data points
1,254
Deep
Time-Shifted Correlation
See how correlation changes when one series is offset in time. A taller bar at a non-zero shift means the two move together better when one leads the other — that's a potential lead/lag signal.
Correlation by shift
Click a bar to inspect. Range: -6 to 6 days.
Selected shift
No shift
Correlation at this shift
+47%
No shift — both series at their actual dates.
1,253 overlapping points at this shift
Baseline
+47%
No-shift correlation, matching the main time-series chart above.
Peak shift
No shift
+47%
A non-zero peak suggests one series lines up better when shifted against the other.
Stability
How the correlation evolves over time. A stable line means the relationship is reliable; large swings signal regime-dependent behavior.
Do They Crash Together?
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
+37%
97 periods · Return correlation when both series rose
Both Falling
+45%
78 periods · Return correlation when both series fell
Diverging
-59%
74 periods · Return correlation when series moved apart
Scatter
0
A: 0 / B: 0
Duplicates removed
0
A: 0 / B: 0
Alignment drops
0
A: 0 / B: 0
Series A
BERKSHIRE HATHAWAY Class B (BRK.B)
BRK.B
Stock · 1,254 raw → 1,254 prepared
Series B
Fastenal Co (FAST)
FAST
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
0.6599
Linear regression slope.
Intercept
0.0001
Linear regression intercept.
Saved 2 weeks ago · ID: stock-brk.b_stock-fast_daily_5y