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Yes, a Stock Can Have Short Interest Over 100% -- Here's How

By Dan Caplinger - Updated Jan 28, 2021 at 11:12AM

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We're all learning a lot about the mechanics of selling stocks short.

Recent events have thrust the practice of selling a stock short into the spotlight. With companies like GameStop (GME -4.79%) and AMC Entertainment Holdings seeing their shares soar as the result of short squeezes, everyone's getting an education about the dynamics of short-selling and how it actually works.

In this latest short-selling controversy, many investors have been confused by the sheer level of exposure that short-sellers have to certain stocks. For instance, GameStop recently had short interest that exceeded 100% of its available shares. That left many investors completely gobsmacked -- but there's a simple explanation for how situations like the one we're currently in can come about.

Hand squeezing blue stress ball.

Image source: Getty Images.

How to short a stock

If you want to sell a stock short, here's a simple guide to the process:

  • Go to your broker and find out if your target has shares available for you to borrow. If so, borrow the shares.
  • Take the shares that you've borrowed and sell them on the open market.
  • At some future date, buy back the shares, hopefully at a price that's cheaper than what it was when you sold the shares.
  • Pocket the difference if the stock has dropped since you sold it short, or find money elsewhere to make up the deficit if the shares got more expensive in the interim.

That sounds simple, but there are some facts to remember. If it's hard for your broker to find shares that you can borrow, you may end up having to pay a borrowing charge to get the stock to sell short. The investor who loans you the shares has the right to get them back at any time with little notice. Ordinarily, your broker will find other shares that you can borrow in their place. If shares just aren't available, the broker generally has the right to close your short position automatically.

Round and round shares go

At first glance, it might seem like you could never have more than 100% of a company's shares sold short. Once all the shares have been borrowed, you might think there wouldn't be any more for short-sellers to get.

Indeed, there are U.S. Securities and Exchange Commission regulations designed to prevent what's known as "naked" short selling. With a naked short sale, the broker allows the customer to do a short-sale transaction without actually arranging to borrow the shares beforehand. This can lead to market disruptions, and while there are some exceptions to the regulations, most brokers stop regular retail customers from selling stock short if they can't obtain shares to borrow.

However, even without a naked short sale, it's theoretically possible for short interest to exceed 100%. The reason has to do with the nature of the short-sale transaction itself.

As an example, take a situation involving four investors. Annie owns shares of GameStop, and Annie and her broker have an agreement that allows the broker to lend Annie's shares to short-sellers. It lends them to Bob, who subsequently sells those borrowed shares short in hopes that GameStop's share price will fall.

An investor named Chris ends up buying those borrowed shares from Bob. However, Chris has no way of knowing that those shares have been borrowed from Annie. To Chris, they're just like any other shares.

More importantly, if Chris has the same kind of agreement, then Chris's broker can lend out those shares to yet another investor. Diane, another GameStop bear, can borrow those shares and sell them short.

In this example, the same shares end up getting borrowed and sold twice. The short interest volume these transactions add to the total is twice the number of shares actually involved. You can therefore see that if this happened throughout the market, total short interest would eventually exceed the number of shares outstanding and approach 200%.

This still might seem impossible, and in a sense, it is. But part of the answer lies in the fact that there are investors that don't currently possess actual shares of GameStop but who have the same economic interest as shareholders. They have the right to get back the shares they lent at any time. When you add together the actual shares plus these "synthetic" positions in the stock, the short interest can't exceed 100% of that larger total.

The big risks of short sales

Given this ability to multiply the number of available shares into massive short positions, a short squeeze could have a cascade effect. When GameStop's share price goes up, both Bob and Diane are under pressure to cover their positions. Yet to do so, they each have to find available shares they can buy and return to Annie and Chris, respectively. When sellers aren't readily available, they'll have to pay through the nose to entice them. That's how the short squeeze accelerates.

Add to that the fact that risks on short sales are potentially unlimited, and you can understand why so many people advise against short-selling at all. As crazy as the current stock market environment has been with stocks that are heavily sold short, the silver lining is that it will likely encourage millions of investors to avoid using this risky strategy in their own portfolios.

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