Efficient markets models assert that the price of each asset is equal to the optimal forecast of its ex-post (or fundamental) value, but the models do not imply that the covariances between prices equal the corresponding covariances of ex-post values. We present bounds for covariances and...

Real stock prices seem to overreact to changes in long-term interest rates. That is, real stock prices drop when long-term interest rates rise (and rise when they fall) more than would be implied by a rational expectations present value model where expectations are based on a vector...

Simple efficient markets models imply that the covariance between prices of speculative assets cannot exceed the covariance between their respective fundamentals unless there is positive information pooling. Positive information pooling occurs when there is more information, in a sense defined...