Various models proposed to explain the equity premium or risk‐free rate puzzle are explained: external habits (Abel’s “catching up with the Joneses” model and the Campbell‐Cochrane model), rare disasters, Epstein‐Zin‐Weil utility, long run risks, and idiosyncratic uninsurable labor income risk. External habits allow the SDF to be variable without requiring high variability of consumption. The SDF for a representative investor with Epstein‐Zin‐Weil utility depends on consumption and the market return. It is most useful when the world is not IID, as in the long‐run risks model. With uninsurable labor income risk, there is no representative investor even if investors all have the same CRRA utility, and there is additional exibility to explain asset returns.
Portfolio Choice with Internal Habit Formation: A Life-Cycle Model with Uninsurable Labor Income Risk