摘要：Empirical studies consistently report that labour productivity and TFP rise with
city size. The reason is that cities attract the most productive agents, select
the best of them, and make the selected ones even more productive via various
agglomeration economies. This paper provides a microeconomically founded model
of vertical city differentiation in which the latter two mechanisms
(`agglomeration' and `selection') operate simultaneously. Our model is both rich
and tractable enough to allow for a detailed investigation of when cities
emerge, what determines their size, and how they interact through the channels
of trade. We then uncover stylised facts and suggestive econometric evidence
that are consistent with the most distinctive equilibrium features of our model.
We show, in particular, that larger cities are both more productive and more
unequal (`polarised'), that inter-city trade is associated with higher income
inequalities, and that the proximity of large urban centres inhibits the
development of nearby cities.
关键词：entrepreneur heterogeneity, firm selection, agglomeration, income inequalities,
urbanization, urban systems
