A planner and agent in a permanent-income economy cannot observe part of the state, regard their model as an approximation, and value decision rules that are robust across a set of models. They use robust decision theory to choose allocations. Equilibrium prices reflect the preference for...

The article presents a historical review of the literature related to the empirical problem of excessive risk premium. The risk premium (the difference between the return on equities and risk-free rate) observed in financial markets cannot be reconciled with theoretical models of financial...