The Capital Asset Pricing Model in conjunction with the usual market model assumptions implies that well-diversified portfolios should be mean variance efficient and ,hence, betas computed with respect to such indices should completely explain expected returns on individual assets. In fact,...

The efficient markets hypothesis has dominated modern research on asset prices. Asset prices and their intrinsic values differ in inefficient financial markets but difficulties in the measurement of intrinsic value greatly complicate market efficiency tests. Reflections on the measurement of...

These notes discuss three aspects of dynamic factor pricing (i.e., APT) models. The first one is that diversifiable idiosyncratic risk is unpredictable in a no-arbitrage world. The second feature is that the conditional factor loadings or betas on the common factors are approximately constant...