Coagglomeration, Clusters, and the Scale and Composition of Cities
构建了一个模型，解释城市中部分产业共集聚而非完全专业化或多样化的中间情形，为产业集群分析提供理论基础，并挑战了城市规模与构成主要由集聚效率驱动的传统观点。
Cities are neither completely specialized nor completely diverse. However, prior research has focused almost entirely on the polar cases of complete specialization and complete diversity. This paper develops a model that can also generate the intermediate case of cities that feature the coagglomeration of some but not all industries, thus giving theoretical foundations to the analysis of business clusters. The analysis sharply challenges the conventional wisdom that the size and composition of cities are necessarily driven primarily by agglomerative efficiencies.