This paper estimates the effect on international trade of multilateral trade agreements - the World Trade Organization (WTO), its predecessor the General 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 50 years and 175 countries. An extensive search reveals little evidence that countries joining or belonging to the GATT/WTO have different trade patterns from outsiders, though the GSP seems to have a strong effect.
Rose, Andrew, K.
2004."Do We Really Know That the WTO Increases Trade?"American Economic Review,