We derive asset-pricing and portfolio-choice implications
of a dynamic incomplete-markets model in which consumers are
heterogeneous in several respects: labor income, asset wealth, and
preferences. In contrast to earlier papers, we insist on at least
roughly matching the model's implications for
heterogeneity — notably, the equilibrium distributions of income and
wealth — with those in U.S. data. This approach seems natural:
Models that rely critically on heterogeneity for explaining asset
prices are not convincing unless the heterogeneity is quantitatively
reasonable. We find that the class of models we consider here is
very far from success in explaining the equity premium when
parameters are restricted to produce reasonable equilibrium
heterogeneity. We express the equity premium as a product of two
factors: the standard deviation of the excess return and the market
price of risk. The first factor, as expected, is much too low
in the model. The size of the market price of risk depends crucially on the
constraints on borrowing. If substantial borrowing is allowed, the
market price of risk is about one one-hundredth of what it is in the data
(and about 15% higher than in the representative-agent model).
However, under the most severe borrowing constraints
that we consider, the market price of risk is quite close to the observed
value.