Vanna and Charm Effects on Options: How Volatility and Time Drive Hedging Flows

Beyond delta and gamma, two second order Greeks significantly impact market structure: Vanna and Charm. These effects are less discussed but can drive substantial flows, especially around volatility events and option expirations.

Vanna: Volatility's Impact on Delta

Vanna measures how delta changes when implied volatility changes. Mathematically, it's the second derivative of option price with respect to both underlying price and volatility.

Practical implications of Vanna:

• Volatility crush after events: When IV drops after earnings, options lose delta. If dealers were hedged, they must sell shares.
• Volatility expansion: Rising IV increases delta of OTM options, requiring additional hedging.
• VIX correlation: Vanna creates a mechanical link between VIX and SPX/SPY moves.

Charm: Time's Impact on Delta

Charm measures how delta changes as time passes, independent of price movement. It's often called "delta decay."

Charm effects are most pronounced near expiration (OTM deltas decay rapidly toward zero), over weekends (two days of time decay with no trading), and for ITM options (delta increases toward 1.0 as expiration approaches).

For market makers with large OTM option positions, charm creates a natural hedging unwind over time. This can contribute to "melt up" dynamics as put hedges are slowly lifted.

Combining Vanna and Charm

Sophisticated analysis considers both effects together. A declining VIX environment with approaching expiration creates dual tailwinds: vanna flows from volatility compression plus charm flows from time decay. This combination has historically contributed to year end rallies and low volatility grinds higher.