Dealer Positioning: What Options Market Makers See
Why dealers are forced to hedge
When a retail trader buys an SPX call, a dealer is short that call. The dealer's risk is now directional — if SPX rises, the short call loses money. To cancel the directional risk, the dealer buys SPX exposure (futures, ETF shares, or basket equivalents). That is the delta hedge. The amount of underlying needed changes continuously as price moves; that is gamma. The amount it changes as time passes is charm. The amount it changes as implied volatility moves is vanna.
None of this is optional for the dealer. Failure to hedge would mean carrying huge naked directional exposure overnight, which violates risk limits at every regulated market maker. The hedging flow is therefore mechanical — and predictable.
The dealer book is not a single number
People talk about "the dealer book" as if it were one position. It is not. It is the superposition of roughly six independent dimensions:
- Net Delta (DEX): how directional the dealer's hedged position is right now. Negative DEX = dealer must keep buying as price falls.
- Net Gamma (GEX): how aggressively the dealer must hedge as price moves. The sign of GEX flips the entire intraday character of a session.
- Net Vega (VEX): how exposed the dealer is to changes in implied volatility. Determines whether the dealer is squeezed by a VIX spike or relieved by it.
- Net Vanna: the cross-term between vol and spot. Drives "vol-up + spot-down" feedback loops in stress.
- Net Charm: the rate of delta decay from time passing. Dominates the dealer's mid-afternoon hedging flow into expiration.
- Net Speed/Color/Higher-order: third-derivative effects that matter near 0DTE and on event days only.
A complete read of dealer positioning means reading all six axes at once. GEXRadar surfaces them in the Greeks tab and the Metrics widget.
How to read the sign of the book
The single most useful question is: are dealers long gamma or short gamma right now?
When dealers are long gamma (positive GEX), every move generates rebalancing flow that pushes price back toward heavy strikes. Realized vol compresses. Daily ranges contract. Mean-reversion intraday strategies work better than trend-following.
When dealers are short gamma (negative GEX), every move generates rebalancing flow in the same direction as the move itself — selling into weakness, buying into strength. Realized vol expands. Breakouts persist. Trend-following intraday strategies work better than fades.
This is a regime change, not a level — and it changes more often than most traders realize. Tracking it live (not from yesterday's close-of-day estimate) is one of the highest-leverage things a discretionary index trader can do.
Where positioning lives — strike by strike
The aggregate sign of the book matters at the macro level; the strike-by-strike concentration matters at the tactical level. Heavy positive gamma at a single strike becomes a wall: dealer hedging accelerates as price approaches, and the wall acts as resistance (call wall) or support (put wall) depending on the side.
On GEXRadar, the GEX-by-strike chart is the most direct view of this. The biggest bar on the call side is the call wall. The biggest bar on the put side is the put wall. The crossover point — where positive gamma gives way to negative — is the gamma flip.
Limits of "dealer positioning" as a concept
Real dealers hedge across multiple instruments, on different rebalancing schedules, with bilateral risk offsets that no public data captures. Public open-interest data assumes calls are dealer-short and puts are dealer-long, which is true on average but not perfectly true at any single strike. Treat the GEX signal as a directionally-correct map, not a precision instrument.
What public data can tell you with confidence: whether dealer hedging in aggregate is stabilizing or amplifying, where the largest concentrations of forced flow sit, and how those concentrations are shifting between expiries. Those three pieces of information are enough to build an edge.