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The Mechanics of a Meme Stock Rally
“Meme stocks” like AMC and GameStop have captured the attention of the financial world. But few understand what is actually driving these furious price rallies. Let’s dive into the mechanics of a meme stock rally…
First off, what is a meme stock? There is no single definition, but meme stocks can be understood as stocks that experience rapid upward price movements as a result of collective social media evangelism. The price movements are typically not related to business fundamentals.
AMC and GameStop are the two most salient examples of meme stocks from recent memory. Both experienced furious, Reddit-fueled rallies that left the financial establishment scratching their heads. Heroes emerged, like fearless leader Roaring Kitty (who is not, in fact, a cat!).
But how did it happen? Emotion (FOMO!) and the power of crowds played a role, but I’ll leave those to the sociologists and psychologists to analyze. There are two underlying financial dynamics at play: a short squeeze and a gamma squeeze.
Let’s cover the mechanics of each…
The Short Squeeze
First, a short squeeze. The "short" in "short squeeze" refers to the concept of short selling. The basics are covered in my thread below. TL;DR - short selling is a way of betting against a stock - i.e. betting that its price will decline.
"Short interest" is a measure of how heavily an asset is shorted by the market. It is the total number of shares that have been sold short (borrowed and sold), but have not yet been covered (bought and returned). It is usually measured as a % of the # of shares outstanding.
A "short squeeze" occurs when a heavily-shorted asset experiences a rapid upward price movement. When this happens, short sellers may be forced to close their short positions (i.e. buy the stock and return it to the broker), further accelerating the upward price movement.
In the case of the recent meme stocks, as AMC or GameStop stock rose, short sellers were forced to close their shorts all at once. This created a surge of buying (to return the borrowed shares) and drove the price up further. It created an accelerating upward price movement.
The Gamma Squeeze
So that’s a short squeeze, but what about a gamma squeeze? It’s a bit more complicated, but let's attempt to simplify it here...
A gamma squeeze is all about options contracts and their indirect impact on the underlying stock. For a primer on options, see my thread below.
When you buy a call option on AMC, someone has to sell you that option contract. You pay them a bit of money (the premium) and they make a commitment to deliver you the underlying stock at a future date for the strike price of the option. It's a pretty simple transaction.
But in the background, the seller (often called a "market maker") has to think about their risk exposure. If AMC rises above your strike price, they will have to buy the stock at the market price and sell it to you for the strike price, incurring a (potentially large!) loss.
To hedge this risk, when the market maker sells you the option, she also goes into the market and buys a bit of the underlying stock. The amount of stock she buys is based on the "Delta" - a ratio of how much the option price moves relative to a $1 move in the stock.
"Gamma" is the rate of change of the "Delta" of the option. As Delta and Gamma rise, the market maker gets more and more nervous! She has to buy more stock to hedge the risk of the option being exercised in the money (i.e. with the underlying price above the strike price).
So here we have the (simplified!) makings of the gamma squeeze. As call option purchasing volumes on AMC suddenly surged, market makers had to purchase a lot of AMC stock to hedge. This set in motion a self-fulfilling prophecy...
Market makers rushed to purchase AMC stock to hedge exposure. This drove the price of AMC up! As the price of AMC went up, the Delta and Gamma of AMC call options rose. This meant market makers had to buy more stock, further driving up the AMC price! Reflexivity.
So to summarize: With AMC and GameStop (and other meme stocks!), we had both (1) a short squeeze - short-sellers frantically buying the stock to close/cover their shorts and (2) a gamma squeeze - call option market makers frantically buying the stock to hedge their exposure.
The result? Check the charts…
I hope this piece was helpful and makes you feel more well-informed on what is happening under the surface with meme stocks!
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Until next time, stay curious, friends!
The Mechanics of a Meme Stock Rally