Ruling Out Multiplicity and Indeterminacy: The Role of Heterogeneity

It is well known that economies of scale that are external to the individualdecision makers can lead to self-fulfilling prophecies and the multiplicityor even indeterminacy of equilibrium. We argue that the importance of thissource of multiplicity and indeterminacy is overstated in representativeagent models, as they ignore the potential stabilizing effect ofheterogeneity. We illustrate this in a version of Matsuyama's (1991)two-sector model with increasing returns to scale. Two main results areshown. First, sufficient homogeneity with respect to individual productivityleads to the instability and non-uniqueness of a given stationary state andthe indeterminacy of the corresponding stationary state equilibrium. Second,sufficient heterogeneity leads to the global saddle-path stability and theuniqueness of a given stationary state and the global uniqueness ofequilibrium.