Informal organizations over time: Why do member states increase delegation?

States are increasingly using informal international organizations (IOs) to pursue agreements in global governance. One of the main advantages of these IOs for member states is that their design constrains the amount of authority that can be delegated to them, thereby reducing sovereignty and reputational costs. However, we continue to have limited knowledge about what happens to the design of informal organizations over time. In this article, I argue that while members strategically limit the authority delegated to an informal IO at the foundational stage, this design preference may change over time. In the context of the global governance of money laundering and terrorism financing, I illustrate my argument by comparing the design of the Financial Action Task Force (FATF) at different points over 30 years. Drawing on institutional documents and elite interviews, I show how increased delegation can occur when an informal IO needs unforeseen technical expertise to efficiently handle a policy area affecting powerful members.