THE MAGNITUDE AND CAUSES OF AGGLOMERATION ECONOMIES
综述了集聚经济的证据，即企业和工人在大城市生产率更高，并探讨了共享、匹配和学习等成因，指出对城市中学习机制的理解仍不足。
ABSTRACT Firms and workers are much more productive in large and dense urban environments. There is substantial evidence of such agglomeration economies based on three approaches. First, on a clustering of production beyond what can be explained by chance or comparative advantage. Second, on spatial patterns in wages and rents. Third, on systematic variations in productivity with the urban environment. However, more needs to be learned about the causes of agglomeration economies. We have good models of agglomeration through sharing and matching, but not a deep enough understanding of learning in cities. Despite recent progress, more work is needed to distinguish empirically between alternative causes.