Twin diplomacy: Strategic co-author selection and resolution outcomes at the UNSC

International Organizations (IOs) foster cooperation among states. But even as members of the same institutions, states do not equally engage with all peers. On what basis are partners selected? While previous studies often measured inter-state cooperation at the United Nations Security Council (UNSC) through co-voting, these connections can be uncoordinated or require little interaction. Instead, I claim that inter-state cooperation can be more effectively assessed by focusing on jointly drafted resolutions. Analyzing a network of 12,000 dyads and data on the authors of 300 drafts on complex humanitarian emergencies during 1990–2018, I find that states searching for co-authors favor peers with similar domestic attributes (regime, wealth, region and political-economic groups). In-group cohesion varies across clusters, but political alikeness emerges as the strongest predictor of cooperation. However, the short-term benefit of “drafting with friends” comes at long-term costs. There is tentative evidence that drafts prepared by diverse coalitions are more likely to be (unanimously) adopted and rarely face vetoes. The regression data are enriched by 74 interviews with United Nations diplomats and a case study on the Second Intifada. The article shows how states’ tendency to engage with similar partners can undermine the efficiency of Council decision-making, encouraging the adoption of more inclusive drafting practices.