Volatility Skew¶
OVERVIEW¶
Volatility skew describes the pattern where options contracts on the same underlying with the same expiration but different strike prices carry different implied volatilities. In equity markets, put options struck below the current price consistently carry higher implied volatility than calls with equivalent distance above — a configuration called negative skew or put skew. The pattern is not random; it reflects the market's chronic demand for downside protection and the empirical reality that equity crashes are sudden while rallies are gradual. Vol skew is one of the most information-dense signals in the options market.
HOW VOLATILITY SKEW IS MEASURED¶
Skew is quantified by comparing implied volatility at different option strikes or delta levels.
| Method | Formula | Interpretation |
|---|---|---|
| 25-Delta Risk Reversal | IV(25Δ call) − IV(25Δ put) | Negative value = put skew; puts cost more than equivalent calls |
| Skew Ratio | IV(OTM put) / IV(ATM option) | Values above 1.0 indicate a put skew |
Tip
The term structure of skew describes how the skew ratio changes across expirations. Short-dated skew is typically steeper around binary events such as earnings announcements or FOMC meetings.
Worked Example¶
With SPY trading at $520 in early 2025:
| Strike | Type | Implied Volatility |
|---|---|---|
| $546 (+5%) | Call | 12% |
| $520 (ATM) | Call / Put | 14% |
| $494 (−5%) | Put | 19% |
The 25-delta risk reversal is approximately −5 vol points. A trader selling the $494 put collects significantly more premium than they would selling the equivalent-distance $546 call. This difference is not mispricing — it is the risk premium the market charges for tail exposure.
WHEN TRADERS USE VOLATILITY SKEW¶
Options traders monitor skew to compare the current fear premium against historical norms, identifying whether downside protection is cheap or expensive relative to its own history. A steep put skew signals institutional hedging demand and often precedes broad distribution. Volatility arbitrageurs trade "skew" by taking opposing positions across strikes and delta-hedging the underlying, profiting when skew normalizes. Risk reversal traders sell expensive puts and buy cheap calls when skew reaches extreme levels, targeting a return to the mean. Skew also determines the relative attractiveness of credit spreads: wide skew makes put spreads richer than call spreads for the same width.
Tip
Use the Tapeboard skew chart alongside IV Rank to determine whether skew is elevated relative to both its own history and the broader volatility environment.
LIMITATIONS AND MISCONCEPTIONS¶
Skew does not predict the direction of the underlying — it reflects the cost of hedging, not certainty of a move. Elevated put skew can persist for months in calm markets. Skew can invert in melt-up environments where call demand dominates, as occurred during certain meme-stock episodes in 2021. Comparing raw IV numbers across strikes ignores delta, which changes as the underlying moves. Skew also varies by sector: technology stocks show steeper skew than utilities, and single-name skew behaves differently from index skew because index puts hedge entire portfolios, commanding a structural premium.
Note
Skew analysis is most reliable when combined with additional context: term structure, open interest distribution, and the current macro event calendar.