Waves of Creative Destruction: Firm-Specific Learning-by-Doing and the Dynamics of Innovation
构建了一个包含知识溢出的重复创新模型，企业同时在产品质量（有溢出）和分销成本（无溢出）两个维度竞争，发现企业特定的干中学效应会降低长期平均创新水平并导致创新活动的内生性波浪。
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, where one firm's innovation ultimately spills over to other firms; and (2) distribution costs, where there are no spillovers across firms and where learning-by-doing on the part of incumbent firms gives them a competitive advantage over would-be entrants. Such firm-specific learning-by-doing has two important consequences: (1) it can in some circumstances dramatically reduce the long-run average level of innovation; (2) it leads to endogeneous bunching, or waves, in innovative activity.