Earnings release asserting growth/record results · run dated 2026-08-14

What happens to a stock when an earnings release describes results as strong?

What the move actually looks like

The mechanism, before the headline number: when the move happens, whether it started early, and whether it lasts.
QuestionWhat 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? +0.08% over the week before filing, against +0.02% 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? -0.58% over the two weeks after the initial reaction, against a filing-day move of +0.73% — so the first move largely stands rather than unwinding.

These three are descriptive figures covering every filing in this category (6,008 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

+0.72%
average abnormal return on the filing day itself, across all companies — and it held at +0.76% on later filings the pattern was not found in, and +0.66% on a separate set of companies

Across all companies, filings in this category moved the stock +0.72% on average on the filing day itself (discovery sample, 4,466 filings, run dated 2026-08-14). The pattern replicated out of sample on both validation axes: +0.76% on later filings and +0.66% on a separate set of companies.

The positive-tone counterpart. The effect is real and replicates on both validation axes, but it is much smaller than the guidance effects — what a company says about the quarter that just ended matters less than what it says about the quarter ahead.

The figures

Average abnormal return, in percentage points. Discovery is where the pattern was found; both holdout columns are data it was then tested on and had not seen.
WindowDiscoveryLater-filings holdoutDifferent-companies holdout
filing day+0.72%
n=4,466
+0.76%
n=1,547
+0.66%
n=2,972

How this was measured

Filings were sorted into categories by reading the text of the release itself and recording what it asserts — not by comparing it to analyst expectations, which this dataset does not hold. Those labels were checked two ways: a structural pass confirming every filing got exactly one valid label in the right order, and an independent re-labelling of a sample by a model from a different lab, with agreement reported as a statistic rather than asserted. Only categories whose agreement cleared the project's threshold appear on these pages.

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

Cite this

Every figure on this page comes from the run named below. Quote the run date with the number.

FlinchLab. What happens to a stock when an earnings release describes results as strong?. Historical SEC 8-K Market-Reaction Dataset, version 0.1.0, run dated 2026-08-14. https://flinchlab.com/answers/stock-reaction-strong-earnings-language

Get the data

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.

Download the free sample — eight rows, all twenty columns, no email address needed. Then decide.

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What is in the file

A forward-looking version — the same classification applied to filings as they arrive — does not exist yet and has no date. If that is the one you would actually use, say so here. What people ask for is how the order of work gets decided.

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