The NATO Advanced Research Workshop on “A reappraisal of the efficiency of financial markets” -- Section 1 Survey Papers -- What do we know about stock market “efficiency”? -- Stock price reversals and overreaction to new events: A survey of theory and evidence -- Comments -- Seasonal...

Diffusion models for volatility have been used to price options while ARCH models predominate in descriptive studies of asset volatility. This paper compares a discrete-time approximation of a popular diffusion model with ARCH models. These volatility models have many siimilarities but the...

We measure the volatility information content of stock options for individual firms using option prices for 149 US firms and the S&P 100 index. We use ARCH and regression models to compare volatility forecasts defined by historical stock returns, at-the-money implied volatilities and model-free...

This paper illustrates regression and Kalman filtering methods for estimating the time-varying term structure of volatility expectations revealed by options prices. Short- and long-term expectations are estimated for four currencies using daily PHLX options prices from 1985 to 1989. Throughout...