Do We Really Know that the WTO Increases Trade?

This paper estimates the effect on international trade of multilateral trade agreements: the World Trade Organization (WTO), its predecessor the Generalized Agreement on Tariffs and Trade (GATT), and the Generalized System of Preferences (GSP) extended from rich countries to developing countries. I use a standard gravity' model of bilateral merchandise trade and a large panel data set covering over fifty years and 175 countries. An extensive search reveals little evidence that countries joining or belonging to the GATT/WTO have different trade patterns than outsiders. The GSP does seem to have a strong effect, and is associated with an approximate doubling of trade.