Gravity variables such as distance, adjacency, colony, free trade agreements or language are used to capture the effects of trade costs in empirical studies. By using actual data on trade costs, this paper decomposes the overall effects of such variables on trade into those through three gravity...

Many developing countries display remarkably high degrees of urban concentration that are incommensurate with their levels of urbanization. The cost of excessively high levels of urban concentration can be very high in terms of overpopulation, congestion, and productivity growth. One strand of...