Zero-days-to-expiration options — contracts that expire on the same day they are traded — now account for approximately half of all daily S&P 500 options volume, up from less than 5 percent in 2016. This structural transformation of the options market has fundamentally altered how volatility is priced, how market makers hedge, and how the VIX — the benchmark measure of expected stock market volatility known as the "fear gauge" — reflects actual market risk. The VIX no longer means what most investors think it means. Understanding why requires understanding the mechanical relationship between 0DTE flows, dealer gamma positioning, and the intraday suppression of realized volatility.
What 0DTE Options Are
A 0DTE option is an equity index option contract whose expiration date is the current trading day. Until 2022, S&P 500 options expired only on Mondays, Wednesdays, and Fridays. The Cboe Global Markets expanded the schedule to offer daily expirations for S&P 500 options on every trading day, creating a continuous stream of zero-day contracts available from market open to close.
The appeal to traders is leverage. A 0DTE option costs a fraction of a longer-dated contract because it has no time value remaining — its price consists entirely of intrinsic value (if in the money) or the probability of moving into the money before the close. An out-of-the-money 0DTE call on the S&P 500 might cost $1.00 per contract and pay $50.00 if the index moves 50 points in the right direction during the trading day. The leverage ratio can exceed 50 to 1.
The appeal to institutions is precision. A portfolio manager who wants to hedge a specific event — a Fed announcement, an earnings release, an economic data print — can purchase 0DTE protection that expires the same day, avoiding the cost of carrying multi-day premium for a risk that resolves within hours.
How 0DTE Flows Suppress the VIX
The VIX is calculated from the prices of S&P 500 options with 23 to 37 days until expiration. It measures the market's expectation of volatility over the next 30 days. The VIX does not incorporate 0DTE options because they have less than one day of remaining life — they are outside the calculation window by definition.
This creates a structural disconnect. The majority of options volume now occurs in contracts the VIX does not measure. The risk that traders are actively pricing and hedging — intraday volatility — is invisible to the index that most investors use to assess market fear.
The suppression mechanism operates through market maker hedging. When a retail or institutional trader buys a 0DTE call, the market maker who sells it must delta-hedge — buying the underlying S&P 500 futures to neutralize directional risk. As the market rises, the delta of the sold call increases, forcing the dealer to buy more futures. As the market falls, the delta decreases, forcing the dealer to sell futures. This is negative gamma positioning for the market maker — their hedging activity amplifies the market's directional moves.
But 0DTE contracts expire within hours. The gamma exposure is intense but brief. Market makers hedge aggressively during the trading day but have no overnight position to carry. The result is that intraday volatility can be extreme — the S&P 500 routinely moves 1 to 2 percent intraday — while close-to-close volatility remains muted because the hedging flows wash out by the end of the session. The VIX, which measures expected close-to-close volatility over 30 days, reflects the muted outcome and registers low readings that do not capture the intraday turbulence.
The Gamma Pinning Effect
On days with extremely high 0DTE volume concentrated at a single strike price, market maker hedging creates a gravitational effect — the index is "pinned" to the strike where gamma exposure is highest. The mechanics are mechanical, not conspiratorial. As the index approaches the high-gamma strike from below, dealers who are short calls at that strike buy futures to hedge, pushing the index toward the strike. As the index overshoots above the strike, dealers sell futures as their hedge ratio adjusts, pulling the index back.
The result is a market that oscillates around a strike price for hours, generating minimal net movement but significant intraday noise. This is the "vol suppression" effect that 0DTE critics cite — the VIX registers low readings because the index finishes the day near where it started, even though it traveled a wide intraday range. The apparent calm is manufactured by the hedging mechanics, not reflective of genuine investor sentiment.
The Tail Risk: What Happens When It Breaks
The suppression mechanism works in normal conditions. It fails during genuine dislocations — events that overwhelm the hedging capacity of market makers or that arrive outside regular trading hours (when 0DTE contracts cannot be traded and hedges cannot be adjusted).
A flash event — a sudden move of 3 percent or more in minutes — forces market makers to hedge at prices far from their initial positioning. The selling (or buying) required to re-establish delta neutrality can amplify the very move the dealers are trying to hedge, creating a feedback loop where hedging activity drives the market further from equilibrium rather than stabilizing it. The February 2018 "Volmageddon" event, the March 2020 pandemic circuit breakers, and the August 2024 carry trade unwind all demonstrated that suppressed volatility does not mean absent volatility — it means stored volatility, released in concentrated bursts when the suppression mechanism fails.
The 0DTE market has not been tested by a genuine financial crisis. The daily expiration structure means that positions clear every day, which limits the buildup of leveraged directional bets that characterized previous derivatives crises. But the concentration of dealer gamma at specific strikes creates fragility points — levels where the market's behavior is determined not by fundamental valuation but by the mechanical hedging requirements of options dealers. The investor who uses the VIX as a measure of market safety is reading an instrument that no longer measures what it was designed to measure.