What it means
Markets absorb information through headlines, news alerts, social media and automated news feeds. Algorithms and busy human traders may react to a few words, such as "profit warning" or "regulator probes", before reading the full article.
The first move therefore reflects the tone of the headline as much as the substance. Several behaviours feed the effect.
People give extra weight to information that is vivid and recent, a bias known as availability, and they tend to follow what others appear to be doing. When many investors react the same way at the same time, price moves can overshoot.
For a business, headlines matter beyond share prices. A negative story can affect a company's borrowing costs, supplier terms, customer confidence and staff recruitment, even if the story is later corrected.
A finance team should have a plan for responding quickly to news, including who speaks to investors and lenders and what figures are ready. Analysts study the effect using event studies, which compare actual price moves around a news event with what the market was expected to do.
The difference is called the abnormal return. A large abnormal return that later reverses suggests an overreaction to the headline, while one that holds suggests the news contained real information.
The nuance is that headlines are not always misleading; sometimes the first reaction is right and the correction never comes. Investors should read the underlying document, compare it with what was already expected and avoid trading in the first confused minutes unless they have a clear plan.
Companies can help by publishing facts quickly, since a vacuum of information is usually filled by speculation. Analysts also remember that a headline about something already widely expected may move prices very little.
In practice
Real-world examples.
Example
A pharmaceutical firm's share price falls 8% in minutes after an alert says a drug trial "failed to meet its goal". Later in the day, the full release shows the main goal was met and only a secondary goal was missed, and the share regains half the fall.
Example
A bank's share price rises on a headline about a takeover approach. Traders buy before reading the article, which describes a rumour from an unnamed source, and the price slips back when the company denies it.
Example
A small exporter reads a headline about new tariffs on its main market and rushes to renegotiate its prices. Its finance manager waits for the official notice, finds the tariff applies only to a product line that the exporter does not sell, and avoids a costly mistake.
Formula
Calculation
Abnormal return = actual return - expected return
Suppose a retailer's share closes at $40.00 on Monday. A headline on Tuesday reads "retailer under investigation", and the share closes at $37.60, while the wider market falls 0.5% that day and the retailer normally moves in line with the market.
Step 1: Actual return = (37.60 - 40.00) / 40.00 = -2.40 / 40.00 = -6.0%.
Step 2: Expected return = -0.5%.
Step 3: Abnormal return = -6.0% - (-0.5%) = -5.5%.
If the share is worth 5.5% less than it otherwise would be, the fall wipes out $2.20 per share (0.055 x 40.00). On a company with 10,000,000 shares, that is $22,000,000 of market value. When the full story emerges and the share recovers to $39.20, the correction has recovered 1.60 / 2.20, or about 73%, of the initial reaction.Case study
Seen in the real world.
Northgate Foods is a fictional listed company whose share price dropped 9% after a news site ran the headline "Northgate recalls products". The finance director found that the recall covered a single batch worth about $150,000, a tiny fraction of annual sales of $240,000,000.
The company issued a clear statement within an hour, with figures and an insurance estimate. The share recovered about two thirds of the fall by the close of the next day in this illustrative case, and the board adopted a rule to publish facts quickly and in plain numbers so that the headline could not do the talking.
Watch out
Common mistakes.
- Trading on the headline alone, when the underlying document often contains context that changes the meaning.
- Assuming every sharp move is an overreaction, when sometimes the news is genuinely important and the price correctly adjusts.
- Ignoring the effect on the business itself, when lenders, customers and staff also react to headlines.
Questions
People also ask.
What is an abnormal return?
It is the difference between a security's actual return and the return expected from normal market behaviour, used to measure the effect of an event.
Does the headline effect fade?
Often partly, because as details emerge prices adjust, although the speed and size of the correction vary.
How can a company limit the damage of a bad headline?
It can respond quickly with specific facts and figures, designate a spokesperson and keep lenders and key investors informed directly.
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