The Lerner Symmetry Theorem: Generalizations and Qualifications -- by Arnaud Costinot, Ivan Werning

The Lerner Symmetry Theorem (Lerner, 1936) establishes the equivalence between import tariffs and export taxes in a simple neoclassical economy with two countries, two final goods, and no trade costs. In this paper we provide a number of generalizations and qualifications of this well-known result. Among other things, we show that the absence of trade deficits is neither necessary nor sufficient for Lerner Symmetry to hold. We conclude by discussing its implications for border tax adjustments.