Equity option markets routinely show a steepening of the implied volatility skew in the days before corporate earnings because market participants price in a higher probability of large, asymmetric moves and because of supply-demand and hedging frictions that amplify downside premia. This pattern reflects both model-based inference about jump risk and behavioral demand for protection.
Market structure and jump expectations
Models that incorporate discrete jumps imply heavier tails and a more pronounced skew than diffusion-only models. Jim Gatheral at Baruch College explains in The Volatility Surface that when investors expect a possible large negative surprise, implied volatility for out-of-the-money puts rises more than for calls, producing a steeper skew. Peter Carr at New York University has emphasized that earnings are classic jump events where distributional assumptions shift away from smooth returns, so pricing must reflect nonlinearity and asymmetric risk premia. Traders therefore embed a higher cost for downside insurance into option prices ahead of announcements.
Demand, supply and hedging dynamics
Human behavior and market microstructure intensify that pricing. Retail and institutional investors tend to seek downside protection before earnings, increasing demand for puts and pushing up their implied volatilities relative to calls. Market makers respond by selling protection and dynamically hedging, which forces gamma and vega exposures that are costly to manage. Those hedging flows can mechanically widen the skew as dealers demand compensation for the risk of large jumps. Robert Engle at New York University has documented how volatility clustering and conditional heteroskedasticity make short-term volatility forecasts sensitive to anticipated events, reinforcing pre-earnings premia.
Consequences extend beyond option prices. A persistently steeper skew raises the cost of protective strategies, alters the fair values used by volatility traders, and creates transient arbitrage opportunities for participants able to carry the risk across the announcement. Culturally and territorially, the effect is most visible in markets where quarterly reporting is tightly scheduled, such as United States equities, and in stocks where earnings carry outsized informational content relative to market capitalization. Nuanced differences emerge between large caps with liquid options and small caps with thin markets, where supply constraints amplify the skew more dramatically.
In sum, the consistent pre-earnings steepening of the skew is a synthesis of expected jump risk, concentrated demand for protection, and the hedging behavior of intermediaries, all interacting within the institutional rhythms of earnings seasons.