Waves of Creative Destruction: Customer Bases and the Dynamics of Innovation

This paper develops a model of repeated innovation with knowledge spillovers. The model's novel feature is that firms compete on two dimensions: 1) product quality or cost, where one firm's innovation ultimately spills over to other firms; and 2) distribution costs, where there are no spillovers across firms and where incumbent firms' existing customer bases give them a competitive advantage over would- be entrants. Customer bases have two important consequences: 1) they can in some circumstances dramatically reduce the long-run average level of innovation; 2) they lead to endogenous bunching, or waves, in innovative activity.