Capacity Utilization and Market Power

We propose a theoretical macroeconomic model where capacity underutilization follows from idiosyncratic demand uncertainty at the time monopolistic firms must choose their productive capacity. After their investment decision, firms facing a low demand will typically prefer to run excess capacities rather than reduce their profit margin; firms at full capacity will respond to demand fluctuations solely by price adjustments. We show that the proportion of firms with idle capacities influences crucially the short-run response of the economy to exogenous disturbances and, in particular, the relative importance of price and quantity adjustments.