What Do Market Makers Actually Do?
Options market makers provide liquidity by continuously quoting bid and ask prices on options contracts. When a retail or institutional trader wants to buy calls, a market maker sells those calls. When someone wants to buy puts, a market maker sells those puts. Market makers profit from the bid-ask spread, not from directional bets on the market. To keep their profits clean and avoid directional risk, they must continuously hedge their exposure, and that hedging process is what moves markets.
The Basics of Delta Hedging
Delta measures how much an option's price changes for each dollar move in the underlying. A call option with a delta of 0.50 gains $0.50 for every $1.00 rise in the stock. When a market maker sells that call, they are short delta, they lose money if the stock goes up. To neutralize this, they buy shares of the underlying stock proportional to the delta.
If a market maker sells 100 call contracts (each covering 100 shares) with a delta of 0.50, they need to buy 5,000 shares (100 x 100 x 0.50) to be delta-neutral. As the stock price moves, delta changes, and the market maker must adjust their hedge. This continuous adjustment is what creates the mechanical flows that GEX and other gamma-based metrics capture.
Dynamic Hedging in Practice
Delta is not static. It changes with every tick in the underlying price (that rate of change is gamma), with every change in implied volatility (vanna), and with the passage of time (charm). This means market makers are constantly recalculating and adjusting their hedges.
Consider a market maker who is short 1,000 SPX call contracts at the 5,000 strike with 5 days to expiration. At the start of the day with SPX at 4,980, the delta might be 0.40, requiring a hedge of 40,000 deltas (1,000 contracts x 100 multiplier x 0.40; in practice, S&P 500 futures contracts). If SPX rallies to 4,995 during the day, delta increases to 0.48, and the market maker must buy additional futures to cover the gap. If SPX drops to 4,960, delta falls to 0.30, and they sell futures.
This creates a cycle: the market maker sells into rallies and buys into dips when they are long gamma (stabilizing), or buys into rallies and sells into dips when they are short gamma (destabilizing).
Why Dealer Positioning Matters for Everyone
Even if you never trade options, dealer hedging is part of the market you trade in. Positive-gamma hedging leans against moves, the condition associated with tight ranges and frequent reversals. Negative-gamma hedging adds to moves, the condition associated with explosive moves and trends that extend.
The Role of Vanna and Charm
Beyond basic delta-gamma hedging, market makers must also manage vanna and charm exposure:
Vanna hedging: When implied volatility drops (as it usually does during rallies), call deltas increase and put deltas decrease. This forces market makers to sell more shares to stay hedged, creating an additional headwind for rallies. Conversely, when IV rises during selloffs, vanna flows force market makers to sell even more, amplifying the decline.
Charm hedging: As time passes, out-of-the-money options lose delta while in-the-money options gain delta. This time-based delta drift requires daily hedging adjustments even if the underlying price stays flat. Charm flows are particularly strong heading into options expiration, one reason OPEX weeks are watched for unusual price behavior.
How to Track Dealer Hedging
SquawkFlow publishes daily-settled GEX levels and the modeled dealer regime derived from them. The gamma levels, GEX flip, and Swing Line describe where open-interest-based hedging pressure may concentrate. They do not observe the direction or magnitude of intraday dealer trades.
The key takeaway: market makers are not predicting the market. They are reacting to it with predictable, mathematically driven behavior. Understanding that behavior explains part of how the market moves, without saying where it goes next.