Claim check: Ether follows Bitcoin
“Ethereum follows Bitcoin: when BTC moves, alts follow a few days later.”
What the data says
Does not hold Not supported by the data: the strongest correlation between Bitcoin's return and Ether's return on a later day was 0.049 at a lag of 2 days (t = 2.8), against 0.78 on the same day; that is too small to matter, since a correlation of 0.10 would explain only 1% of the variation.
No effect we can tell from chance, or the opposite effect.
Who says it
Alt season narratives on YouTube.
Origins are as commonly cited and were not independently verified.
How we tested it
Correlation between Bitcoin's return on day t and Ether's return on day t+1, t+2 and t+3, on common dates. A real lag effect needs a correlation of at least 0.10 with a t-stat above 2.4 (slightly stricter than 2 because three lags are examined) and a positive sign in both halves.
Results
| Lag (days) | Correlation | t-stat | First half | Second half |
|---|---|---|---|---|
| 1 | -0.046 | -2.7 | -0.049 | -0.041 |
| 2 | 0.049 | 2.8 | 0.052 | 0.039 |
| 3 | 0.019 | 1.1 | 0.022 | 0.009 |
Correlation with the later days' return, by lag
Stability across the two halves of history
A saying that only works in one half of the history is not much of a rule. Each row shows the effect in the full history, the first half and the second half; green means the claimed effect was present.
| Market | Full history | First half | Second half |
|---|---|---|---|
| Bitcoin / Ether | 0.049 | 0.052 | 0.039 |
Context and cross-checks
Shown for context; not part of the verdict.
Same-day correlation
| Pair | Days | Correlation | First half | Second half | Reading |
|---|---|---|---|---|---|
| Bitcoin / Ether | 3288 | 0.78 | 0.76 | 0.84 | Clear and stable |
Correlation by year
| Year | Correlation |
|---|---|
| 2018 | 0.81 |
| 2019 | 0.82 |
| 2020 | 0.84 |
| 2021 | 0.76 |
| 2022 | 0.90 |
| 2023 | 0.83 |
| 2024 | 0.80 |
| 2025 | 0.82 |
| 2026 | 0.91 |
The honest caveat
Daily closes can't detect intraday lags; same-day correlation dominates.
Descriptive statistics from historical data, before costs. Not a forecast and not investment advice.
Questions
Ethereum follows Bitcoin: when BTC moves, alts follow a few days later.
Not supported by the data: the strongest correlation between Bitcoin's return and Ether's return on a later day was 0.049 at a lag of 2 days (t = 2.8), against 0.78 on the same day; that is too small to matter, since a correlation of 0.10 would explain only 1% of the variation.
How was this claim tested?
Correlation between Bitcoin's return on day t and Ether's return on day t+1, t+2 and t+3, on common dates. A real lag effect needs a correlation of at least 0.10 with a t-stat above 2.4 (slightly stricter than 2 because three lags are examined) and a positive sign in both halves.