I develop a novel view of the trade frictions between rich and poor countries by arguing that to reconcile bilateral trade volumes and price data within a standard gravity model, the trade frictions between rich and poor countries must be systematically asymmetric, with poor countries facing...

Recent studies argue that cross-country labor productivity differences are much larger in agriculture than in the aggregate. We reexamine the agricultural productivity data underlying this conclusion using new evidence from disaggregate sources. We find that for the world's staple...

Cross-country labor productivity differences are larger in agriculture than in non-agriculture. We propose a new explanation for these patterns in which the self-selection of heterogeneous workers determines sector productivity. We formalize our theory in a general-equilibrium Roy model in which...