Results of operations (earnings) · run dated 2026-08-14
How much does a stock typically move on the day a company reports earnings?
What the move actually looks like
| Question | What the data says |
|---|---|
| How much lands before the open? | About 55% of the typical move on the filing day happens overnight, between the previous close and the open, rather than during the trading session. By the time the market opens, most of the reaction to this kind of filing has already happened. |
| Did it move before the filing? | +0.13% over the week before filing, against +0.12% over an earlier baseline stretch of the same earnings filings — both small next to the reaction itself, so the filing looks like the moment the information arrives. |
| Does the first move hold? | -0.31% over the two weeks after the initial reaction, against a filing-day move of -0.15% — so the first move largely stands rather than unwinding. |
These three are descriptive figures covering every filing in this category (11,235 of them), which is why their sample size differs from the validated figure below — that one is measured on the discovery slice and re-tested on two holdouts. No significance is claimed for the three above, and the pre-filing figure is shown against its own control window rather than as a finding in its own right.
The headline number
The typical move is +6.10% on the filing day itself, measured without regard to direction, across 11,241 filings (run dated 2026-08-14). The average direction over the same filings is -0.15%, which is close to nothing — large moves in both directions cancel out.
This is the dataset's positive control: earnings days are known in the finance literature to produce large moves, so if this measurement had come back small it would have meant the pipeline was broken rather than the literature being wrong. It also shows why direction and size are separate questions — the typical move is large while the average direction is close to nothing.
The figures
| Window | Average move | Typical size of move | Filings |
|---|---|---|---|
| filing day | -0.15% | +6.10% | 11,241 |
| filing day + 1 | -0.20% | +6.62% | 11,241 |
| filing day + 5 | -0.36% | +7.49% | 11,241 |
How this was measured
This category is the official SEC item code as the company filed it. No reading of the filing text is involved, so the category rests on filing metadata alone.
For each filing we compare the stock's actual return against what that specific stock would have been expected to return given how the market moved that day. The expectation comes from the stock's own prior trading history, fitted over a window that ends well before the filing, so the filing itself cannot influence its own benchmark. The difference between actual and expected is the abnormal return, and the figures above are averages of that difference, in percentage points.
Many categories are tested at the same time, so the results are corrected for multiple comparisons. Direction and size are corrected as separate families. The windows before the filing are corrected as a family of their own. Figures from different families are not comparable to each other.
Why the holdout columns matter
A pattern found by searching a dataset will often not survive being tested on data it was not found in. Every finding on this page was discovered on one slice, frozen as a written prediction, and then tested on two untouched slices: later filings the discovery step never saw, and a separate set of companies with no overlap. A finding appears here only if it held up on both. Findings that failed this test are kept in the record and reported as refuted rather than deleted.
Limitations you should read before citing this
- Averages, not predictions. These are historical averages across many filings. Individual filings vary enormously around them, and nothing here forecasts what any future filing will do.
- Survivorship. The company universe is built from current index membership, so it leans toward companies that still exist and are still in the index.
- Daily resolution. Reactions are measured on daily closing and opening prices, not intraday ticks.
- No expectations data. The dataset does not know analyst consensus, so it never claims a company beat or missed. Categories describe what a filing asserts, nothing more.
- Counts shift between runs. The universe is rebuilt each run and companies enter and leave, so event counts move even when nothing about the method changes. Every figure here is quoted with its run date for that reason, and effect sizes travel better than counts.
- US only, bounded window. One market, and a fixed multi-year window ending at the run date.
- Overlapping windows. Companies file often, so longer windows around different filings can overlap.
Cite this
Every figure on this page comes from the run named below. Quote the run date with the number.
FlinchLab. How much does a stock typically move on the day a company reports earnings?. Historical SEC 8-K Market-Reaction Dataset, version 0.1.0, run dated 2026-08-14. https://flinchlab.com/answers/how-big-is-an-earnings-day-move
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This page carries a single finding. The complete historical layer is a non-recurring, dated, versioned file. It holds every validated finding with the out-of-sample holdout columns, classification below the raw filing categories, the full aggregate grid, the data dictionary and the methodology.
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