In a world in which INGOs play such a large and fraught role, this book explores why they make the choices they do. In this chapter, we first review the book’s theory and its contributions. Next, we recap our empirical findings. We then consider how our theoretical framework might be extended to understand dynamics among INGOs headquartered in countries outside the United States and to explore cross-sectoral variation. We also consider growth in other populations of global governance actors – especially for-profit development firms, direct-giving campaigns, and domestic NGOs – and how these actors may be challenging INGOs’ dominance. We offer reflections on how the trends we identified in this book might influence INGOs’ effectiveness. Finally, we consider the study’s implications for public and private funders working with INGOs to affect social change.