What Is VEX?
VEX — Vanna Exposure — measures the aggregate vanna risk dealers carry across all open options contracts. While GEX explains how dealers hedge against price moves, VEX explains how they hedge against volatility moves.
Vanna is the rate at which an option's delta changes as implied volatility (IV) changes. When IV rises or falls, every option's delta shifts — and dealers must re-hedge to stay neutral. That re-hedging creates real buying and selling pressure in the underlying, regardless of whether price has moved at all.
How Vanna Works
Consider a dealer who sold a call option:
- The call has a delta of 0.35 and the dealer is short that delta (sold the call, bought stock to hedge)
- If IV rises, the call's delta increases toward 0.50 — the call behaves more like the stock
- The dealer now has too much stock. They must sell to rebalance
- If IV falls, the call's delta shrinks toward 0.20 — the dealer has too little stock. They must buy
This dynamic runs across thousands of contracts simultaneously. The net effect is:
- IV spike → dealers sell the underlying (vanna headwind)
- IV crush → dealers buy the underlying (vanna tailwind)
Positive and Negative VEX
Positive VEX — dealers are net long vanna from calls above the market
- IV rising → dealers reduce delta exposure → sell pressure on the underlying
- IV falling → dealers increase delta exposure → buy pressure on the underlying
- Result: a vol crush after a fear event can trigger a sharp rally driven entirely by vanna flows, even without new bullish catalysts
Negative VEX — dealers are net short vanna, typically from puts below the market
- IV rising → dealers increase delta exposure → buy pressure (counterintuitive — but puts behave differently)
- IV falling → dealers reduce delta exposure → sell pressure
When VEX Matters Most
VEX flows are strongest when implied volatility is moving rapidly:
- Post-event vol crush — after FOMC, earnings, or CPI, IV collapses fast. Vanna-driven buying can fuel a rally that looks fundamental but is purely mechanical
- VIX spike days — when VIX jumps 10–20%, vanna flows from call deltas shrinking can add to selling pressure
- Monday open after a fear Friday — weekend vol premium bleeds out Sunday night, triggering vanna buying before the cash open
On low-IV, calm days, vanna flows are minimal and GEX dominates. VEX becomes the primary driver when vol is on the move.
Reading VEX on gammaflowpulse
The VEX map shows vanna exposure by strike price. Key things to look for:
- Large positive VEX above current price → a vol crush from this level will generate mechanical buying — useful context after a fear spike when you're looking for a reversal
- Large negative VEX below current price → a vol spike with price near this level can amplify selling as dealers re-hedge
- VEX and GEX alignment — when vanna and gamma flows point the same direction, moves are stronger and cleaner. When they conflict, expect choppier, less decisive price action
VEX vs GEX — Which Dominates?
- IV stable, price moving → GEX dominates
- IV moving, price stable → VEX dominates
- Both moving → Both active — direction depends on sign of each
- Post-event vol crush → VEX dominates (vanna tailwind often drives the rally)
- VIX spike, market falling → Both negative — amplified selloff
Practical VEX Checklist
Before an event (FOMC, CPI, earnings):
- Check the sign and magnitude of VEX above the current price
- Large positive VEX + expected vol crush = mechanical buying likely post-event
After a spike day:
- If VIX has risen sharply and VEX is positive above current price, the next vol compression could fuel a sharp recovery — watch for it
Intraday:
- If price is flat but the underlying is rallying without obvious cause, check whether IV is falling — vanna flows may be the driver