Daily research · The economy and Wall Street · written
What does Ether do the day after a big S&P 500 down day?
Short answer
The middle case of 55 since 2018 saw Ether move −0.60% the day after a big S&P 500 down day. 55% of the cases ended lower. The best 1 in 10 reached +9.6% or more, the worst 1 in 10 −9.0% or less. Out of sample, calls like it showed no clear edge.
Typical move
−0.60%
the next day, the middle case
How often
55%
it ended lower
Best 1 in 10
+9.6%
or better
Worst 1 in 10
−9.0%
or worse
Cases
55
2018-2026, on 55 days
Higher 45% of the time against 52% on ordinary days (55 days compared): no clear edge over ordinary days.
Share on Xcopy link§ 01 · The pattern55 cases
The pattern, exactly
as of · the rule, the data, the dates
A case is the day after the S&P 500 closed 2% or more down (FRED), and the move that counts is Ether's.
Each of the 55 moves is measured from the close before the event's day to the close 1 day after that day.
In our data that gives 55 measured cases on 55 separate days, from Feb 3, 2018 to Jun 6, 2026; the numbers were written on Nov 7, 2026.
§ 02 · Why it might work
Why it might work
as of · the idea traders have in mind, not a promise
When US stocks fall this hard in a day, risk is being cut across markets, and the worry is that crypto is dumped together with stocks. Traders watch whether crypto follows, shrugs it off or rebounds.
That is the reasoning behind watching S&P 500 drops; whether it held over our 55 cases since 2018 is what the next sections measure.
§ 03 · How we tested it
How we tested it
as of · our own closes, against ordinary days
- Every one of the 55 cases is measured from the close before the event's day to the close 1 day after that day, on our own daily closes (UTC).
- Each case is set against Ether's own ordinary days (1-day moves starting in the 365 days before it, at least 90 of them), and 55 of the 55 days had that many to compare.
- No two cases share a day, so each of the 55 days counts once.
- Out of sample: each calendar quarter, the lab re-ran its coin-by-coin search on the data before that quarter only, then scored every call the proven drivers of this kind made in the quarter after, against how often the same side won on any day of the same coin's quarter.
§ 04 · Results21 up · 17 down
Results
as of · every past case, Feb 3, 2018 to Jun 6, 2026
A day later, the middle case stood at −0.60% and the average day at +0.70%; 21 cases ended up, 17 down and 17 sideways (within ±2.2%).
ended up (21)ended down (17)sideways, within ±2.2% (17)each line one real case · past cases, not a projection
1, 7 and 30 days against ordinary days
| After | Cases | Typical move | Typical, ordinary days | Higher | Higher, ordinary days | Against ordinary days |
|---|---|---|---|---|---|---|
| 1 day this post | 55 | −0.60% | +0.09% | 45% | 52% | no clear edge over ordinary days |
| 7 days | 55 | −0.66% | +0.33% | 47% | 51% | no clear edge over ordinary days |
| 30 days | 55 | +0.55% | −0.84% | 51% | 49% | no clear edge over ordinary days |
At the other horizons: 7 days, typical −0.66% over 55 cases; 30 days, typical +0.55% over 55 cases.
By year, the typical move ranged from −3.6% in 2018 to +6.6% in 2021; 4 of 7 years leaned the same way as the whole.
Year by year
| Year | Cases | Typical move | Higher | Lower |
|---|---|---|---|---|
| 2018 | 7 | −3.6% | 14% | 86% |
| 2019 | 5 | −1.2% | 40% | 60% |
| 2020 | 10 | +1.1% | 50% | 50% |
| 2021 | 5 | +6.6% | 80% | 20% |
| 2022 | 16 | −1.00% | 44% | 56% |
| 2023 | 1 | −0.56% | 0% | 100% |
| 2024 | 4 | −2.8% | 0% | 100% |
| 2025 | 5 | +2.3% | 80% | 20% |
| 2026 | 2 | +3.6% | 100% | 0% |
The latest 10 cases
| Day | What happened | 1 day | 7 days | 30 days |
|---|---|---|---|---|
| S&P 500 fell 4.4% in a day | open | open | open | |
| S&P 500 fell 2.6% in a day | +6.8% | +6.2% | +13.7% | |
| S&P 500 fell 2.1% in a day | +0.44% | +2.4% | −33.0% | |
| S&P 500 fell 2.7% in a day | +8.4% | +1.6% | −6.8% | |
| S&P 500 fell 2.2% in a day | +0.73% | +12.2% | +56.9% | |
| S&P 500 fell 3.5% in a day | +8.0% | +4.4% | +65.2% | |
| S&P 500 fell 4.8% in a day | −0.62% | −13.8% | −0.46% | |
| S&P 500 fell 2.7% in a day | +2.3% | +3.6% | −18.4% | |
| S&P 500 fell 2.9% in a day | −4.3% | −8.0% | −8.8% | |
| S&P 500 fell 2.1% in a day | −2.3% | −3.5% | −0.45% |
1 case still open: the 1-day window of the newest closes on Nov 7, 2026.
Source: our daily closes and our dated events, measured on .
§ 05 · Out of sampleno clear edge out of sample
Out of sample
as of · calls like it, scored on data they never saw
Out of sample, calls made from S&P 500 drops showed no clear edge: right 69% of 16 calls since 2020, against 46% for that side on any day (Oct 28, 2020 – Nov 5, 2026).
The bar to earn a side: right more often than that side won on any day, on 100+ scored calls over 60+ separate days, with an average move its way above 0%; the share above is that record's, not the in-sample rate of the 55 cases here.
§ 06 · Verdict
Verdict
as of · plain, with the caveats
No clear edge: 45% of 55 days ended higher against 52% on ordinary days, inside the range chance alone gives (33% to 58%).
A typical −0.60% hides a wide spread: one case in 10 was beyond +9.6% and one in 10 beyond −9.0%.
Out of sample, calls like it showed no clear edge (right 69% of 16 calls since 2020, against 46% for that side on any day).
With 55 cases, one case moves the share that ended lower by 1.8 points.
Markets change, so what S&P 500 drops did from 2018 to 2026 can stop working.
§ 07 · Questions
Questions
as of · answered from the numbers above
- How often did Ether end lower the day after a big S&P 500 down day?
- In 55% of 55 cases from Feb 3, 2018 to Jun 6, 2026.
- Measured the scoreboard's way, day by day, the share higher was 45% against 52% on Ether's own ordinary days.
- How big was the move the next day?
- The middle case moved −0.60% the next day.
- The best 1 in 10 reached +9.6% or more and the worst 1 in 10 −9.0% or less.
- Is this an edge?
- Not on its own: over 55 cases it shows no clear edge over ordinary days, and out of sample, calls like it showed no clear edge (right 69% of 16 calls since 2020, against 46% for that side on any day).
- The −0.60% typical move is the past's, and a past pattern can stop working.
- When did it last happen?
- The latest was on Nov 6, 2026: S&P 500 fell 4.4% in a day.
- Its 1-day window closes on Nov 7, 2026.
- Does it depend on the year?
- No. The typical move was +6.6% in 2021 (5 cases) and −3.6% in 2018 (7 cases).