How Activist Short Sellers Move a Stock

When activist short sellers call out an overvalued company, they publish a detailed report, and sometimes take it further by putting a number on it: a target price showing how far they believe the stock should fall. In our research with Alexandre Madelaine and Wuyang Zhao, we show what that number does. On average, stocks fall about 5% on the day of a short-selling attack and the next trading day – but they fall an extra 1.4 percentage points in that same window when the short seller’s report includes a target price. In short, the number speeds up the sell-off.

The number that moves markets

To understand why target prices matter, it helps to know how activist short sellers work. A short seller is an investor who borrows a company’s shares, sells them, and hopes to buy them back later at a lower price, pocketing the difference as profit.  

Our research shows a simple pattern: the bigger the drop a short seller predicts, the more the stock actually falls in the months that follow. The target price helps predict the slide in the first month, the next few months, and even up to a year later. Only about 10% of companies ever hit the short seller’s target after a year, but the size of that target still helps predict the slide.  

Activist sShort sellers publish detailed reports, but the target price stands out: 50% appear on the first page, and 43% are highlighted in bold, colour or boxes. That visibility gives the number reach. When a target price appears, the stock draws more attention online, including on X, and the price falls harder on the day of the attack. The market also gets to the new price faster – a sign that the target makes the short seller’s case easier for investors to grasp.

The number that draws fire

Our research shows what happens next. Once a short seller puts a target price on the table, pushback from shareholders starts. A falling share price hurts their holdings, so some cut back the shares they make available to borrow. That tightening reduces supply and raises costs for short sellers.  

Analysts push back too. Sell-side analysts – the ones who publish price targets for investors – raise their own targets when a short seller publishes one, a clear sign they are challenging the short seller’s claims and defending their own view of the company.

Companies do not respond any more than usual. They’re no more likely to sue short sellers or issue public rebuttals when target prices appear. The heat comes instead from investors and analysts. 

Why short sellers show their number

If a sharp, specific prediction can attract challenges or retaliation, then why take the risk? Because target prices help short sellers build credibility. Around half reveal a target price only in some campaigns, and only when they believe their evidence is strong.  

Our research shows that target prices appear when the report is backed by precise information: these reports are longer, use more numbers, cite more sources and include more allegations.

Revealing a target price shapes a short seller’s reputation, and that reputation matters. Our study shows that when a short seller’s past targets were closer to reality, investors trust them more and the stock drops more quickly the next time they launch an attack. In effect, past targets become a track record that determines how seriously the market takes them.

Where retail investors lose out

However, retail investors do not use target prices well. They do not sell more when the predicted drop is bigger, and sometimes they even buy when the warning is mild. Our research shows these trades usually lead to worse results for them, because the stock keeps falling afterwards.

Applications

Target prices change how information moves through the market. Because they are so visible, the numbers quickly focus attention on the company and the short seller’s claims. They also act as a shortcut for investors: a target price signals that the report is backed by stronger evidence and deserves a closer look. The effect is uneven. Professional investors pick up the signal fast, while many retail investors misread it and suffer losses. The study shows how one number can speed up market reactions while widening the gap between those who understand it and those who do not.

Methodology

We analysed 1,237 short-selling campaigns from 2010 to 2018, comparing cases with and without a target price. We tracked how the stock moved on the day of the attack and in the months afterup to a year later. We also looked at what was inside the reports, how much the pool of lendable shares shrank, how analysts reacted, and how the story spread on social media. Finally, we tested reputation by seeing how investors responded when a short seller with a stronger or weaker track record launched a new campaign.