Incomplete Information, Heterogeneity, and Asset Pricing

We consider a pure exchange economy where the drift of aggregateconsumption is unobservable. Agents with heterogeneous beliefsand preferences act competitively on financial and goods markets.We discuss how equilibrium market prices of risk differ acrossagents, and in particular we discuss the properties of the marketprice of risk under the physical (objective) probability measure.We propose a number of specifications of risk aversions andbeliefs where the market price of risk is much higher, and theriskless rate of return lower, than in the equivalent full informationeconomy (homogeneous and heterogeneous preferences) and thuscan provide an(other) answer to the equity premium and risk-freerate puzzles. We also derive a representation of the equilibriumvolatility and numerically assess the role of heterogeneityin beliefs. We show that a high level of stock volatility canbe obtained with a low level of aggregate consumption volatilitywhen beliefs are heterogeneous. Finally, we discuss how incompleteinformation may explain the apparent predictability in stockreturns and show that in-sample predictability cannot be exploitedby the agents, as it is in fact a result of their learning processes.