The last century has witnessed dramatic changes in the world economy. The service (tertiary) sector, which at the beginning of the 20th century was of little importance relative to agriculture and manufacturing, has become the dominant sector today, accounting for 80% and more of value added in...

We derive a simple equation for the welfare gains from trade when tariffs are liberalized or iceberg trade costs fall. Covering various one-sector trade models that may or may not feature extensive margins and imperfect competition, we generalize the analysis of Arkolakis, Costinot and...