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How options dealers' hedging can calm or speed up index moves, and why same-day options matter now.
Options dealers hedge the options they've sold by trading the underlying market. Gamma exposure (GEX) estimates how much hedging they need as price moves. The standard estimate, from SqueezeMetrics, assumes dealers are long the calls and short the puts that the public trades. When total GEX is positive, their hedging tends to buy dips and sell rallies, which dampens moves; when it's negative, hedging chases price, which can make moves bigger.
0DTE options expire the same day. Same-day S&P 500 options reached a record 62.4% of SPX options volume in August 2025, so they now have a large effect on intraday index moves, and estimates based on yesterday's open interest go stale during the day.
Related gauges: max pain (the strike where the most option value expires worthless, which some think price drifts towards near expiry; that's disputed) and the put/call ratio (a sentiment measure). These matter mainly for ES, NQ and other index products.
For education only, not financial advice.