How to read an options volatility smile
Quick answer
An options volatility smile shows implied volatility plotted across strike prices for a single expiry. Equity options typically show a downward skew (OTM puts have higher IV) reflecting demand for downside protection. FX options show a symmetric U-shape. Commodity options often show an upward skew reflecting supply-shock risk. The shape reveals how the market prices tail risk.
What does the volatility smile tell you about market risk?
The volatility smile — the curve of implied volatility across strike prices for a single expiry — is one of the most information-dense objects in finance. In a world where Black-Scholes was perfectly correct, there would be no smile: all options on the same underlying with the same expiry would have the same implied volatility. The fact that they don't reveals the market's true beliefs about risk.
The smile's shape varies dramatically across asset classes, and each shape tells a different story about how the market perceives downside risk, upside potential, and the probability of extreme moves.
Why do equity options have a downward volatility skew?
Options on equity indices (S&P 500, NASDAQ, individual stocks) almost always show a pronounced downward skew. Out-of-the-money puts have significantly higher implied volatility than out-of-the-money calls.
Why? Portfolio managers systematically buy protective puts to hedge downside risk. This demand pushes up the price (and implied vol) of OTM puts. Meanwhile, many investors sell covered calls against their stock holdings, putting downward pressure on OTM call prices.
The steepness of the equity skew is itself informative. A steep skew (big difference between OTM put IV and ATM IV) indicates strong demand for protection — the market is nervous. A flatter skew suggests complacency.
Why do FX options show a symmetric volatility smile?
Currency options often display a genuine symmetric smile — both deep OTM puts and deep OTM calls have elevated IV relative to ATM. This makes intuitive sense: currencies can move sharply in either direction. There's no inherent 'gravity' pulling them lower (unlike stocks, which can go to zero).
The FX smile is often described using 'risk reversals' (the difference between OTM call and OTM put vol) and 'butterflies' (the curvature of the smile). These are standard quoting conventions in FX options markets.
Why do commodity options have an upward skew?
Commodity options, particularly in energy markets, often show an upward skew — OTM calls have higher IV than OTM puts. This reflects supply-shock risk: oil prices can spike 50% in a crisis (embargo, hurricane, war) but are unlikely to halve overnight.
Agricultural commodities show similar patterns: drought, flooding, or disease can cause prices to spike, but bumper harvests provide a soft floor.
How do changes in the volatility smile signal market shifts?
The most valuable information often comes from changes in the smile over time:
Skew steepening before earnings: the market expects a bigger downside move than upside.
Smile widening: increasing uncertainty about the magnitude of the next move, regardless of direction.
Skew flattening after an event: the market is repricing post-event — uncertainty has resolved.
Quadesto can overlay smiles from different dates to make these changes visually obvious. This is the kind of chart that drives engagement in finance newsletters.