Fundamental Analysis · Intermediate · 4 min

Reading earnings reactions on the chart

You can recognize an earnings gap and its volume on a chart, describe whether it held or filled, and explain what research found about drift after earnings.

Easy to spot

Scroll through a year of daily candles for almost any share, and four days stand out. Each shows a sudden jump, an empty space between two candles and a tall volume bar.

Those are usually earnings days. This lesson connects the fundamental side of this rubric with the chart: what an earnings reaction looks like, how traders describe what happens next, and what research says about the days after.

Gap on heavy volume

Companies usually report before the market opens or after it closes. The news therefore arrives while no regular trading takes place. At the next open, the price can start far from the last close, leaving a gap on the chart.

In the fictional chart, the share moves sideways around 49 for 20 days. After the report, candle 21 opens at 56.40, almost 15% above the previous close of 49.20. Volume reaches 4.6 million shares, about four times the usual 1.1 million.

Three things are worth reading on such a day:

The size of the gap. It shows how far the news moved the market's view of the company.
The volume. Heavy volume means many participants traded at the new level, a broad reassessment rather than a few orders.
The close. Candle 21 closes at 57.30, near its high of 58.10. Buyers kept control through the day.

Held or filled

What happens over the following days is often more telling than the first candle.

The price dips to 56.07 on candle 24 but never re-enters the gap below 55.80.
By candle 30, it closes at 57.89.

Traders say the gap held. Had the price fallen back to 49.49, they would say the gap filled, which usually means the market reconsidered the news.

Research has studied the days after earnings for decades. Ball and Brown (1968) and later Bernard and Thomas (1989) found that prices tended to keep drifting in the direction of an earnings surprise for weeks: post-earnings announcement drift. It became one of the most cited exceptions to efficient markets. More recent work, such as Martineau (2022), finds that the drift disappeared for all but the smallest US stocks by the mid-2000s, though other researchers dispute this.

Common mistakes

Holding through earnings without a plan. A gap can jump far beyond a stop order, so the loss can be much larger than planned.
Reading the first minutes as the verdict. Early moves often reverse during the earnings call.
Assuming every gap fills. Many earnings gaps never do.
Treating old research as a strategy. The drift found in older data is much weaker today.

The takeaway

Earnings often show up as a gap with heavy volume. Whether the gap holds over the next days says more than the first move, but it is no forecast.

Check yourself

Quick quiz

4 questions. Instant feedback, nothing is saved.

1Tap the candle that reacted to the earnings report.

Tap the chart.

Candle 21 opened at 56.40 after a close of 49.20, with volume of 4.6 million against about 1.1 million on normal days.
2What does it mean that the gap was not filled in the following days?

A gap that holds shows that the new level was accepted for now. It says nothing certain about the next move.
3What did Ball and Brown (1968) and Bernard and Thomas (1989) describe?

This post-earnings announcement drift was one of the best-known anomalies. Later studies found it much weaker in recent decades.
4Why does volume matter on an earnings gap?

A gap on heavy volume reflects a broad reassessment. A gap on thin volume is easier to reverse.

of 4 correct.

Sources

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