There is a strong connection between per worker productivity and metropolitan area population, which is commonly interpreted as evidence for the existence of agglomeration economies. This correlation is particularly strong in cities with higher levels of skill and virtually non-existent in less...

Empirical research on cities starts with a spatial equilibrium condition: workers and firms are assumed to be indifferent across space. This condition implies that research on cities is different from research on countries, and that work on places within countries needs to consider population,...

Historically, urban growth required enough development to grow and transport significant agricultural surpluses or a government effective enough to build an empire. But there has been an explosion of poor mega-cities over the last thirty years. A simple urban model illustrates that in closed...

Recent theories of economic growth, including Romer (1986), Porter (1989) and Jacobs (1969), have stressed the role of technological spillovers in generating growth. Because such knowledge spillovers are particularly effective in cities, where communication between people is more extensive, data...

We show in a multi-sector, heterogeneous-firm trade model that the effect of tariffs on entry, especially in the presence of production linkages, can reverse the traditional positive optimal tariff argument. We then use a new tariff dataset, and apply it to a 189-country, 15-sector version of...

The purpose of this paper is to identify conditions under which hedonic price indexes provide an exact measure of consumer welfare, so that the welfare effects of quality change can be inferred. Our results are quite positive in providing a rational for existing practices, though the conditions...

Three sources of gains from trade under monopolistic competition are: (i) new import varieties available to consumers; (ii) enhanced efficiency as more productive firms begin exporting and less productive firms exit; (iii) reduced markups charged by firms due to import competition. The first...