Monopoly Power and Endogenous Variety in Dynamic Stochastic General Equilibrium: Distortions and Remedies

We study the efficiency properties of a dynamic, stochastic, general equilibrium, macroeconomic model with monopolistic competition and firm entry subject to sunk costs, a time-to-build lag, and exogenous risk of firm destruction. Under inelastic labor supply and linearity of production in labor, the market economy is efficient if and only if symmetric, homothetic preferences are of the C.E.S. form studied by Dixit and Stiglitz (1977). Otherwise, efficiency is restored by properly designed sales, entry, or asset trade subsidies (or taxes) that induce markup synchronization across time and states, and align the consumer surplus and profit destruction effects of firm entry. When labor supply is elastic, heterogeneity in markups across consumption and leisure introduces an additional distortion. Efficiency is then restored by subsidizing labor at a rate equal to the markup in the market for goods. Our results highlight the importance of preserving the optimal amount of monopoly profits in economies in which firm entry is costly. Inducing marginal cost pricing restores efficiency only when the required sales subsidies are financed with the optimal split of lump-sum taxation between households and firms.