Globalization has promoted the transnational diffusion of public policies. Recognizing that policies of one country are shaped by policies of others, scholars have developed several theories to explain policy diffusion. Because empirical evidence for these theories is contested, this study evaluates the relative explanatory power of the major theories of policy diffusion for human trafficking policies. To test competing theoretical claims, this study uses quantitative methods on an original, cross-national data set to analyze how human trafficking policies diffused. The results reveal that for the diffusion of human trafficking policies coercion and constructivist theories have robust support, while support is less consistent for reputation theory and altogether lacking for competition theory. Surprisingly, the findings show that irresolute sanction threats were more effective than credible threats in promoting trafficking policy diffusion. In addition, the analysis reveals a complicated relationship between regional organizations and constructivist diffusion mechanisms. By showing the explanatory power of each theory and raising new questions and puzzles, the study offers a foundation for further theoretical development. This research also has practical implications for diplomats and policymakers who wish to promote the diffusion of good practices to counter human trafficking
