International non-governmental organizations (INGOs) are today widely acknowledged actors in global affairs and their infl uence has gained increasing attention in scholarly and policy circles. The Union of International Associations (UIA) reports a rise in the number of international NGOs from under 200 in 1909 to several tens of thousands by the 1990s. The number of international non-profi ts registered in the United States (US) almost doubled from 3,548 in 1998 to 6,790 in 2008 (Kerlin and Thanasombat 2006; Wing et al. 2010). Revenue more than tripled during the same time period, from 9.7 billion (1998) to 31.9 billion USD (2008), with much of the gains concentrated among the largest organizations. With the rise of middle-income nations, growth in this sector will shift to non-Western regions and greatly increase the diversity of INGO activism.