Over the past fifty years, barriers to international trade have decreased substantially. A key source of this decline in protectionism has been the proliferation of agreements among countries to liberalize commerce. In this article, we analyze the domestic political conditions under which states have concluded such agreements and, more generally, explore the factors affecting interstate economic cooperation. We argue that interstate cooperation on commercial issues depends heavily on the political regime types of participants: as states become more democratic, they are increasingly likely to conclude trade agreements. To test our claim, we examine whether the regime types of states have influenced their propensity to form and expand preferential trading arrangements (PTAs) during the period since World War II. We find that democratic countries are about twice as likely to form a PTA as autocratic countries, and that pairs of democracies are roughly four times as likely to do so as autocratic pairs. These results provide strong evidence that democracies are more commercially cooperative than less democratic countries.
Edward D. Mansfield is Hum Rosen Professor of Political Science and Director of the Christopher H. Browne Center for International Politics at the University of Pennsylvania, Philadelphia, Pennsylvania. He can be reached at firstname.lastname@example.org.
Helen V. Milner is James T. Shotwell Professor of International Relations in the Political Science Department at Columbia University, New York, New York. She can be reached at email@example.com.
B. Peter Rosendorff is Associate Professor of International Relations and Economics at the University of Southern California, Los Angeles, California. He can be reached at firstname.lastname@example.org.