Institute for Data Analysis and Visualization

In the past five years a relatively extensive literature has emerged that explores the demand for multilateral cooperation, that is, those factors that motivate states to develop (or resist developing) formal institutions that operate to increase interstate economic, military, or environmental cooperation.1 These factors include the transaction costs associated with ad hoc and multiple, bilateral arrangements; increased interstate trade; the diffusion of liberal trade theory; information about the costs of environmental degradation; and trends in elite ideology.To date, however, our understanding of the supply side of multilateralism--the standards that are set for admission, the order and speed with which candidate states are admitted, and the impact of expansion on cooperation and future evolution--has been relatively undeveloped.2 Partly as a result, theorists have had little to say about how multilateral institutions are likely to evolve or what the policy consequences of their expansion will be.3 Supply-side issues are important because multilateral organizations usually do not ''spring forth full blown''--they grow. Instead of forming an ''inclusive'' agreement-- that is, one that covers nearly all of the states that its designers eventually hope to include--many multilateral organizations start out with substantially smaller memberships and generally expand over time. We argue that, among the many possible explanations for the choice of this design strategy, there is a rational choice argument