Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
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.