Vanna Exposure (VEX)
Canonical definition, formula, interpretation rules, and live API reference for dealer vanna exposure.
The net dealer vanna exposure — measures how dealer delta changes when implied volatility moves. Drives the "vol-coupling" effect where IV changes feed back into dealer hedging and price movement.
Where νᵢ is the option vanna (∂δ/∂σ) of contract i, OIᵢ is open interest, S is spot price, sign is +1 for calls and -1 for puts, and the sum is across the entire option chain.
- Positive VEX: vol compression benefits dealers. IV drops push dealer delta long, triggering buying — the "vanna rally" feedback loop.
- Negative VEX: vol spike amplifies delta moves. IV expansion forces dealers to chase, selling into declines and buying into rallies.
- Event sensitivity: VEX is most relevant during events (earnings, FOMC) where IV shifts sharply and vanna flows dominate gamma flows.
Live Example: SPY
Live SPY VEX data temporarily unavailable. See /stock/spy/gamma for current values.
Get VEX via API
symbol(path, required) — underlying ticker, e.g.SPYexpiration(query, optional) — filter to single expiry (yyyy-MM-dd)min_oi(query, optional) — minimum open interest threshold
{
"symbol": "SPY",
"underlying_price": number,
"net_vex": number,
"vex_interpretation": string,
"strikes": [
{ "strike", "call_vex", "put_vex", "net_vex",
"call_oi", "put_oi", "call_volume", "put_volume" }
]
}curl -H "X-Api-Key: YOUR_KEY" \
https://lab.flashalpha.com/v1/exposure/vex/SPYWhy VEX Matters for Trading
VEX measures how dealer delta changes when IV moves. It's the vol-coupling layer above GEX — matters most when VIX is rallying or crashing.
- What it measures
- Net dealer vanna exposure across the chain. Vanna is ∂Δ/∂σ — the second-order cross between spot and vol.
- What it signals
- How aggressively dealers will hedge on vol shocks. High absolute VEX means a VIX spike forces big directional flow; low VEX means vol changes pass through cleanly.
- Why we measure it
- Vol regime shifts are when the market dislocates. VEX quantifies the amplification or damping those shifts produce via dealer flow.
- Who uses it
- Vol traders, VIX desks, event-driven traders, and anyone running short-vol books who needs to size vol-shock exposure.
How to read VEX
- Dealers buy the underlying when IV rises
- Vol-up coincides with supportive flow
- Typical during orderly risk-off (mild spikes)
- Limits downside drawdown
- Dealers sell the underlying when IV rises
- Vol spike + price drop reinforce each other
- Waterfall risk during disorderly risk-off
- Classic crash-signal combo
- Vol shifts produce little dealer flow
- Pure directional regime
- Read GEX instead
- Typical quiet-market reading
Rules of thumb
- VEX matters most at vol extremes. During quiet tape, VEX is noise. The signal lives in VIX spikes and rapid compression.
- Pair with term structure. Backwardation + negative VEX is the canonical crash-amplifying combo.
- Negative VEX + negative GEX = unstable. Both exposure types short gamma means dealer flow amplifies both price and vol shocks.
- VEX rotates through OPEX. Large vanna concentration on near-dated expiries unwinds into expiry — expect vol regime shifts in the weeks after large OPEX.
- Use VEX for vol-timing, not pure direction. VEX predicts how vol shocks propagate, not which way price goes next.
How to Read VEX
VEX operates on a different axis than GEX. While GEX measures how dealer delta changes with price, VEX measures how dealer delta changes with implied volatility. This matters most during events that cause large IV shifts — earnings announcements, FOMC decisions, CPI prints — because the vanna-driven hedging flow can dominate the gamma-driven flow when IV moves are proportionally larger than spot moves.
Positive VEX creates the classic "vanna rally" setup. When IV compresses (e.g., post-earnings IV crush), positive VEX means dealer deltas shift long — they must buy the underlying to stay hedged. This buying pushes price up, which can further compress IV, which triggers more buying. The feedback loop explains why post-earnings moves often overshoot: the vanna flow amplifies the initial direction. Conversely, when IV expands with positive VEX, dealer deltas shift short — they sell, pressuring price downward.
Negative VEX reverses the feedback. Vol compression pushes dealer deltas short (selling), and vol expansion pushes deltas long (buying). This is less common but can occur when the put skew is extreme or when large institutional call overwriting shifts the net vanna position. The practical implication: with negative VEX, the usual "buy the dip after IV crush" playbook fails because the vanna flow works against recovery.
Related Concepts
Net dealer gamma exposure — determines whether dealer hedging dampens or amplifies price moves.
Net dealer delta exposure — the directional bias in dealer hedging across the option chain.
The price level where net GEX crosses zero — the boundary between positive and negative gamma regimes.
The spread between implied and realized volatility — whether options are overpriced relative to actual movement.
The strike with the highest call gamma concentration — acts as intraday resistance in positive-gamma regimes.
Learn More
Complete guide to vanna, charm, and the second-order greeks that drive dealer hedging flows.
Full endpoint reference with parameters, response schema, and tier limits.
Per-strike vanna exposure visualisation for any US equity or ETF.
Live for 6,000+ US symbols. One API call, sub-200ms.
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