Theory and Methods Research Paper 2009 / 06 WTO Membership and the Extensive Margin of World Trade : New

Recent literature has argued that, contrary to the results of a seminal paper by Rose (2004), WTO membership does promote bilateral trade, at least for developed economies and if membership includes non-formal compliance. We review the literature in order to identify open issues. We then develop the simplest possible “corner-solutions" version of the gravity model which serves as a framework to readdress these issues. We focus on the extensive margin of trade that separates positive-trade from zero-trade country pairs. We argue that the model can be consistently estimated using Poisson pseudomaximum-likelihood methods with exporter and importer fixed effects. We account for coding issues and the potential heterogeneity of the WTO membership which recent contributions have stressed. While we find that WTO membership increases the likelihood that a given country pair trades, we do not find that the extensive margin has a strong and systematic effect on the average trade-creating potential of the WTO. JEL classification: F12, F13