Does Net Buying Pressure Affect the Shape of Implied Volatility Functions?


  • Nicolas P. B. Bollen,

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    • Owen Graduate School of Management, Vanderbilt University and Fuqua School of Business, Duke University. We gratefully acknowledge the comments/assistance of Cliff Ball, Alon Brav, Mike Lemmon, Joseph Levin, Joshua Rosenberg, Eileen Smith, Tom Smith and seminar participants at Vanderbilt University, Nashville, TN, and the 2003 American Finance Association meetings, Washington, D.C. We are especially grateful to an anonymous referee for providing many useful and insightful comments and suggestions.

  • Robert E. Whaley


This paper examines the relation between net buying pressure and the shape of the implied volatility function (IVF) for index and individual stock options. We find that changes in implied volatility are directly related to net buying pressure from public order flow. We also find that changes in implied volatility of S&P 500 options are most strongly affected by buying pressure for index puts, while changes in implied volatility of stock options are dominated by call option demand. Simulated delta-neutral option-writing trading strategies generate abnormal returns that match the deviations of the IVFs above realized historical return volatilities.