technological spillovers in generating growth. Because such knowledge spillovers are particularly effective in cities, where … that important knowledge spillovers might be between, rather than within industries, consistent with the theories of Jacobs …

replied: 'Ricardo's theory of comparative advantage'. Truth, however, in Samuelson's reply refers to the fact that Ricardo …'s theory of comparative advantage is mathematically correct, not that it is empirically valid. The goal of this paper is to … output predicted by Ricardo's theory of comparative advantage. Despite all of the real-world considerations from which this …