OEX Put/Call Ratio
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Definition
Put/call ratio for options on the S&P 100 (OEX), historically viewed as a 'smart money' gauge because OEX has been dominated by sophisticated institutional traders.
How to read it
The OEX put/call ratio is often read inversely to the equity-only ratio. OEX (S&P 100 index options) has historically been used by professional traders, so the reasoning goes that when OEX traders buy heavily into puts they are often right, making a high OEX ratio a caution rather than a contrarian positive. It is best treated as a supplementary 'who is positioning' lens alongside the broad equity ratio, and its edge depends on OEX still attracting sophisticated flow.
How practitioners use it
Used as context among multiple indicators — never as a standalone signal to act.
Less common professional uses
The smart-money premise is increasingly contested: liquidity has migrated to SPX, SPY, and 0DTE products, so OEX's 'sophisticated' character has thinned and its historical edge may have decayed; validate on recent data before relying on it. Because OEX is a hedging vehicle, a high ratio can reflect portfolio protection rather than a directional bearish bet, the same interpretation trap as the index put/call. Thin OEX volume makes the ratio jumpy; a single large institutional order can swing it, so weight it less than deeper series. Contrast OEX (professional) against ROBO (retail) for an explicit smart-money-vs-retail spread. Cite the data cadence: OEX volume is exchange end-of-day, not real-time positioning.
Sources & provenance
Cboe OEX (S&P 100) option volume
This page is educational content published by Pachira Aquatica Global LLC. It is not investment advice and not a recommendation.