Explaining the Poor Performance of Consumption-based Asset Pricing Models

We show that the external habit-formation model economy of Campbell and Cochrane (1999) can explain why the Capital Asset Pricing Model (CAPM) and its extensions are betterapproximate asset pricing models than is the standard onsumption-based model. The model economy produces time-varying expected eturns, tracked by the dividend-price ratio. Portfolio-based models capture some of this variation in state variables, which a state-independent function of consumption cannot capture. Therefore, though the consumption-based model and CAPM are both perfect "conditional" asset pricing models, the portfolio-based models are better approximate "unconditional" asset pricing models. Copyright The American Finance Association 2000.