The institutional design of international organizations (IOs) has undergone a transnational transformation during the past two decades. Transnational actors (TNAs), such as non-governmental organizations (NGOs), philanthropic foundations, and multinational corporations, nowadays interact with IOs in all policy fields and at all stages of the policy process. While a growing body of research is engaged in mapping and explaining this development, systematic studies of the effects of TNA access are still in short supply. Addressing the question of when, how, and why TNA involvement matters, this paper seeks to remedy this situation. Theoretically, the paper develops and tests two competing explanations of TNA impact: one privileging information exchange and one privileging social mobilization. Empirically, the paper engages in a statistical analysis of new survey data on TNA access, strategies, and influence in the United Nations (UN). This analysis is supplemented by comparable data from a broader set of IOs, as well as elite-interview data from the UN.
