The possibility of building a mathematical theory of a system or of simulating that system does not depend on having an adequate microtheory of the natural laws that govern the system components. Such a microtheory might indeed be simply irrelevant. Herbert A. Simon, The Sciences of the...

This paper examines the pricing implications of time-variation in assets' market betas over the business cycle in a conditional CAPM framework. We use a half century of real GDP growth expectations from economists' surveys to determine forecasted economic states. This approach largely avoids the...