Strong start, weak finish: a synthetic control analysis of UN arms embargo effectiveness

This study examines the effectiveness of arms embargoes in stopping arms transfers to targeted states. While widely used, the efficacy of arms embargoes remains contested in the literature, partly due to methodological limitations that hinder robust causal inference. To address these challenges, I employ the Synthetic Difference-in-Differences (SDID) approach–a method that improves upon traditional techniques by enhancing pre-treatment fit, accounting for unobserved time-varying confounders, and relaxing the strict parallel trends assumption. My findings show that UN arms embargoes lead to a significant reduction in arms imports by approximately 40% during the first 2 years following their imposition–a considerably larger effect than previously reported. However, this initial impact diminishes over time, likely due to the emergence of circumvention strategies by exporters and the adaptive behaviour of target states.