Smile and Skew Interpretation
Smile and Skew Interpretation
Volatility smiles and skews function like a seismograph for market sentiment—recording fear, complacency, and positioning extremes in the shape of implied volatility across strikes. Reading these patterns reveals actionable intelligence about crowd expectations and potential dislocations.
Equity vs. FX Smile Context
Equity index smiles: Downside skew dominates. OTM puts trade at higher IV than OTM calls because:
- Portfolio insurance demand (puts protect against crashes)
- Fat left tails in equity returns
- Leverage effects (falling prices increase leverage, increase vol)
Typical equity pattern (S&P 500):
| Strike | IV |
|---|---|
| 25Δ Put | 28% |
| ATM | 20% |
| 25Δ Call | 17% |
The 11% difference between 25Δ put and 25Δ call reflects crash protection premium.
FX smiles: More symmetric or even call-skewed depending on the pair:
- USD/JPY: Often put-skewed (yen rallies in crisis)
- EUR/USD: Relatively symmetric
- EM pairs: Fat tails on both sides
Commodity smiles: Often call-skewed for supply-sensitive commodities:
- Supply disruptions cause price spikes
- OTM calls protect against shortages
- Crude oil during geopolitical stress shows call skew
Signals from Risk Reversals and Butterflies
Risk Reversal
Definition: 25Δ call IV minus 25Δ put IV
Equity example: RR = 17% - 28% = -11%
Interpretation: Strong put premium indicates demand for downside protection.
Signals:
- RR more negative than historical: Extreme fear, potentially oversold
- RR less negative than historical: Complacency, reducing hedges
- RR flipping positive: Unusual—investigate for special situations
Butterfly
Definition: Average of 25Δ put and call IV minus ATM IV
Equity example: Butterfly = [(28% + 17%) / 2] - 20% = 22.5% - 20% = 2.5%
Interpretation: Wings trade 2.5 vols above ATM, reflecting tail risk premium.
Signals:
- Butterfly elevated: High demand for tail protection, potential overpay for wings
- Butterfly compressed: Market confident in range trading, possibly complacent
Signal Summary
- Risk reversal deepening (more negative for equities): Fear increasing, consider fading if extreme
- Risk reversal flattening: Complacency, potential vulnerability to shocks
- Butterfly expanding: Tail risk repricing, volatility regime shift possible
- Butterfly compressing: Range expectations, carry strategies favored
Regime Shifts and Data Pitfalls
Regime shift indicators:
- Risk reversal moves >3 vols in a week without corresponding spot move
- ATM IV spikes while skew flattens (volatility of volatility event)
- Term structure inverts (near-term > long-term) suddenly
Data pitfalls:
- Stale quotes in illiquid strikes distort surface
- Large bid-ask spreads make mid-prices unreliable
- Corporate events (earnings, M&A) create local distortions
- Time zone differences create apparent anomalies
Validation checks:
- Compare to prior day's surface
- Cross-check with liquid ETF options (SPY vs. SPX)
- Verify with market maker quotes if available
Translating Signals into Hedge Adjustments
Scenario: Risk reversal reaches -15% (historical range: -8% to -12%)
Interpretation: Extreme fear pricing in puts.
Potential actions:
For existing long portfolio:
- Puts are expensive—consider collar instead of protective put
- Sell OTM puts to fund ATM put (put spread instead of naked put)
- Reduce hedge size if conviction is contrarian
For volatility trading:
- Risk reversal mean reversion trade: Sell put, buy call
- Size conservatively—extreme can become more extreme
Scenario: Butterfly compresses to 1.0% (historical average: 2.5%)
Interpretation: Market underpricing tail risk.
Potential actions:
- Buy OTM strangles (cheap wings)
- Increase gamma exposure if expecting volatility
- Review tail hedges—may be opportunistic to add protection
Action Plan
- Monitor daily: Track RR and butterfly vs. 20-day moving average
- Set alerts: Flag when metrics exceed 2 standard deviations
- Contextualize: Correlate with news, positioning data (COT), and fund flows
- Act gradually: Enter positions in tranches; don't assume immediate mean reversion
- Review outcomes: Track P/L of skew-based trades to calibrate signals
Sample Risk Reversal Data
| Date | ATM IV | 25Δ Put IV | 25Δ Call IV | Risk Reversal | Butterfly |
|---|---|---|---|---|---|
| Week 1 | 18% | 25% | 15% | -10% | 2.0% |
| Week 2 | 20% | 28% | 16% | -12% | 2.0% |
| Week 3 | 25% | 35% | 20% | -15% | 2.5% |
| Week 4 | 22% | 30% | 17% | -13% | 1.5% |
Week 3 shows spike in fear (RR -15%, highest). Week 4 shows partial normalization. A trader fading the Week 3 extreme would have profited as RR reverted.
Next Steps
For understanding how the full surface is constructed, see Implied Volatility Surface Basics.
To explore term structure dynamics, review Volatility Term Structure Modeling.