What is a gamma squeeze?

What people mean by a gamma squeeze

A gamma squeeze is a story about hedging. Traders buy call options. The firms that sold those calls hedge by buying the underlying. As price rises, the hedge needs more shares, and those purchases add to the rise.

A 2021 SEC staff report on early-2021 market events uses the same definition: market makers buying stock to hedge calls they wrote, putting further upward pressure on the price. It names an influx of call buying as one of the main drivers.

The word squeeze makes it sound like a measured event. It is not. It is a hypothesis about who holds which side of the options, and how they hedge.

Sources: U.S. Securities and Exchange Commission staff: Staff Report on Equity and Options Market Structure Conditions in Early 2021.

The mechanics behind the story

Gamma is how much an option’s delta changes for a $1.00 move in the underlying. Long calls and long puts have positive gamma. Short calls and short puts have negative gamma.

A hedger who is short calls and keeps delta flat has to buy as price rises and sell as it falls. That is the short-gamma case: the hedge trades in the direction of the move. Our gamma exposure guide covers the long-gamma case, where hedging can lean against the move.

Gamma is highest for options near the money and close to expiration. So the story needs large open interest in calls that are both near the money and near expiry.

Sources: Options Industry Council (OCC): Gamma.

A fictional example, read two ways

Fictional ETF: price $100.00. Open interest is 20,000 calls at the $102 strike, expiring in three days. Say the model puts each call’s gamma at 0.05.

Read one way, hedgers are short those calls. A $1.00 rise lifts each call’s delta by about 0.05, so the hedge needs about 0.05 × 20,000 × 100 = 100,000 more shares. Buying them would lean with the rise.

Read the other way, hedgers are long those calls. The same $1.00 rise would call for selling about 100,000 shares, leaning against the rise.

The open interest is identical in both readings. Only the ownership assumption changed. This illustration holds gamma constant; real gamma changes with price, time and volatility.

Why open interest cannot confirm it

Every open contract has a long side and a short side. Open interest counts the contracts still open. It does not say which side a market maker holds, whether the position is hedged, or with what.

It also updates slowly. Open interest is an end-of-day count. Cboe DataShop, for example, uses the previous night’s OCC figure for the whole trading day, so positions opened today are not in it yet.

Volume does not settle the question either. Cboe’s study of same-day SPX options makes the point that hedging depends on the balance of buys and sells, not the total size of the volume.

In the episode its staff studied, the SEC report found that market makers were buying, not writing, call options, and staff did not find evidence of a gamma squeeze in the available data. Public open interest alone could not have shown which side market makers held.

Sources: Options Industry Council (OCC): Open Interest: Why It Matters; Cboe DataShop: Frequently Asked Questions; Cboe — Mandy Xu: Much Ado About 0DTEs: Evaluating the Market Impact of SPX 0DTE Options; U.S. Securities and Exchange Commission staff: Staff Report on Equity and Options Market Structure Conditions in Early 2021.

What a GEX chart can and cannot show

A GEX chart models exposure from open interest under a stated sign assumption. Prism’s convention counts calls positive and puts negative. A squeeze story assumes the opposite sign for the calls it is about. The chart can show where those calls sit. It cannot tell you which sign is right.

A squeeze story is not a trade signal

Told after a sharp rise, a squeeze story is easy to fit to the chart. Before the move, the same open interest supports the opposite reading, as the fictional example shows.

Even if hedgers are short gamma, the story does not say how far a move runs, when hedging stops, or whether other sellers absorb the buying. Price can reverse at the strike the story points to.

Treat the label as a question about positioning, not an instruction. Public data cannot confirm it while it is happening.

How this sits in a plan you already have

Use call concentrations as places to watch in a plan you already have. A GEX chart can locate them. It cannot confirm a squeeze, and it does not choose a trade.

• Wait for price at a concentration instead of chasing a move someone has already labeled a squeeze.
• Place the stop beyond structure you can see, not beyond a level the story assumes will give way.
• Compare the nearest expiry with a wider window before treating one call strike as the whole book.
• If the data clock is not current, stand down. A demo or stale book is not a live book.

What remains unknown

Public open interest does not show who holds the calls, whether they are hedged, or with what. It does not show how large any hedging is next to the rest of the market’s trading, or whether positions close before expiry.

A call concentration can hold, fail or disappear as positions change. Check price structure, liquidity and event risk before applying your own risk plan.