Large cities produce more output per capita than small cities. This may occur because more talented individuals sort into large cities, because large cities select more productive entrepreneurs and firms, or because of agglomeration economies. We develop a model of systems of cities that...

This chapter surveys recent developments in agglomeration theory within a unifying framework. We highlight how locational fundamentals, agglomeration economies, the spatial sorting of heterogeneous agents, and selection effects affect the size, productivity, composition, and inequality of...

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...