Case Study · The Gamma Squeeze
Free to readThe Gamma Squeeze — GameStop, January 2021
When a crowd buys calls fast enough, the dealers who sold them are forced to chase the stock higher to stay hedged. That feedback loop has a name: a gamma squeeze.
Dealer gamma usually explains how the index calms or accelerates. GameStop is the case where short dealer gamma on a single name became the engine of the move — a self-reinforcing loop visible in the option chain before it was on every front page.
The setup
Through late January 2021, a coordinated retail bid poured into short-dated GameStop calls. The dealers and market-makers on the other side were now short call gamma — and short gamma means hedging with the move. As the stock rose, their delta got shorter, forcing them to buy more stock to stay flat. That buying pushed the stock higher, which made them shorter still, which forced more buying. A loop.
Call volume explodes. Dealers accumulate short call gamma and begin hedging by buying stock. The feedback loop starts.
The squeeze goes vertical — roughly +1,500% on the run, peaking near Jan 27–28. Short-gamma hedging is now a dominant buyer; every up-tick forces more buying.
Brokers restrict buying; the call bid breaks. The hedging loop stalls and reverses — the accelerant cuts both ways.
Each turn of the loop forces more dealer buying, which lifts price, which deepens the short-gamma hedge. The same mechanism unwinds violently when the call bid stops.
What the gamma read flagged
You didn't need the news to see it. A name with explosive short-dated call open interest and spot pressing up through those strikes is a name where dealer hedging has turned pro-trend. On the tool, that shows as deeply short-gamma positioning with the heaviest gamma stacked at call strikes just overhead — the configuration of an accelerant, not a shock absorber.
A gamma squeeze is short dealer gamma made visible. Heavy call open interest plus spot rising into it means hedging is buying the stock for you — until it isn't. The loop that lifts can reverse just as fast.
This case study is free. To watch dealer gamma on a single name like GME you need ETF + Equities; replay the full GEX history with Everything.
See plans →Your next step
Open the tool → Case study: below the flip, Q4 2018 → Read: trading around the flip →Educational content from Nations Indexes. Event facts (the squeeze dates, the ~1,500% run, the trading restrictions) are historical and verifiable. The gamma description characterizes how dealer hedging likely behaved; the figure is schematic, and nothing here is investment advice.