We reexamine the time-series relation between the conditional mean and variance of stock market returns. To proxy for the conditional mean return, we use the implied cost of capital, computed using analyst forecasts. The usefulness of this proxy is shown in simulations. In empirical analysis, we...

We develop a performance evaluation approach in which a fund manager's skill is judged by the extent to which his investment decisions resemble the decisions of managers with distinguished performance records. The proposed performance measures are estimated more precisely than standard measures,...

We develop a simple approach to valuing stocks in the presence of learning about average profitability. The market-to-book ratio (M/B) increases with uncertainty about average profitability, especially for firms that pay no dividends. M/B is predicted to decline over a firm's lifetime due to...

Implications of factor-based asset pricing models for estimation of expected returns and for portfolio selection are investigated. In the presence of model mispricing due to a missing risk factor, the mispricing and the residual covariance matrix are linked together. Imposing a strong form of...

We develop a general equilibrium model in which stock prices of innovative firms exhibit "bubbles" during technological revolutions. In the model, the average productivity of a new technology is uncertain and subject to learning. During technological revolutions, the nature of this uncertainty...

We survey the recent literature on learning in financial markets. Our main theme is that many financial market phenomena that appear puzzling at first sight are easier to understand once we recognize that parameters in financial models are uncertain and subject to learning. We discuss phenomena...

Not necessarily. The fundamental value of a firm increases with uncertainty about average future profitability, and this uncertainty was unusually high in the late 1990s. We calibrate a stock valuation model that includes this uncertainty, and show that the uncertainty needed to match the...

We develop a model of stock valuation and optimal IPO timing when investment opportunities are time-varying. IPO waves in our model are caused by declines in expected returns, increases in expected profitability, or increases in prior uncertainty about average profitability. The model predicts...

We analyze how changes in government policy affect stock prices. Our general equilibrium model features uncertainty about government policy and a government that has both economic and non-economic motives. The government tends to change its policy after performance downturns in the private...