Efforts against trafficking in human beings increased in the last two decades. Although considerable funds are devoted, little is known about their effectiveness, mainly due to a lack of or insufficient evaluation. This article reviews the quality of and insights from available evaluation reports in the field of demand-side anti-trafficking campaigns. Such campaigns seek to induce behavior change, particularly to abstain from buying goods produced or services delivered under circumstances of exploitation, or to report suspicions to helplines or police. The examination pursues three questions: How are these campaigns supposed to work? What is known about their results? How can learning from campaign experiences be improved? Available evaluation reports show that reporting campaigns tend to work like a funnel. Hundreds of thousands people are targeted but only a handful of people will ever be in a situation to behave as recommended. Messages designed to attract attention can be misunderstood and induce harmful side-effects for victims and suspects. The findings suggest that the watering-can principle of showering time and resources to an external evaluation of each and every project is not appropriate. It is more convincing to select a small share of funded projects for intensive external evaluation and give more support to low-budget internal evaluation for all projects. © 2018 by the Institute of Interdisciplinary Studies in Humanities and Social Sciences, New York.

Evaluation Social justice Campaigns Anti-trafficking measures Demand-side

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