Virtually all theories of economic growth predict a positive relationship between population size and productivity. In this paper I study a particular historical episode to provide direct evidence for the empirical relevance of such scale effects. In the aftermath of the Second World War about...

U.S. county data for the last 20 or 30 years show that manufacturing employment has been deconcentrating. In contrast, the service sector exhibits concentration in counties with intermediate levels of employment. This paper presents a theory where local sectoral growth is driven by technological...