There is a large body of evidence indicating that cross-country differences in income levels are associated with differences in productivity. If workers are much more productive in one country than in another, restrictions on immigration lead to large efficiency losses. The paper quantifies...

Recent theoretical work predicts that an important margin of adjustment to deregulation or trade reforms is the reallocation of output within firms through changes in their product mix. Empirical work has accordingly shifted its focus towards multi-product firms and their product mix decisions....

Despite several theoretical contributions and considerable informal empirical evidence" to the contrary, a notion that trade and investment are substitutes persists in trade policy" analysis. This paper considers the liberalization of commodity trade versus liberalization" allowing direct...

We examine the generalizability of internally valid estimates of causal effects in a fixed population over time when that population is subject to aggregate shocks. This temporal external validity is shown to depend upon the distribution of the aggregate shocks and the interaction between these...