In a world where poor countries provide weak protection for intellectual property rights, market integration will systematically shift technical change in favor of rich nations. For this reason, free trade can increase international income differences. At the same time, integration with...

This paper develops a dynamic general equilibrium model of North-South trade. Northern firms devote resources to innovative R&D to discover higher quality products and Southern firms devote resources to imitative R&D to copy state-of-the-art quality products. Both innovation and imitation rates...

Most economic activity occurs in cities. This creates a tension between local increasing returns, implied by the existence of cities, and aggregate constant returns, implied by balanced growth. To address this tension, we develop a theory of economic growth in an urban environment. We show how...

A large number of pairs of countries exhibit a dynamic pattern in which: (i) Fertility in both countries declines across time; (ii) Initially one country has higher fertility and lower per-capita income compared to the other; (iii) In time, as per-capita income converges, fertility rates in the...

I show that in a conventional Ramsey model, between one-fourth and one-half of the global income distribution can be explained by a single factor: The effect of large, persistent differences in national average IQ on the private marginal product of labor. Thus, differences in national average IQ...