Human trafficking victimization is harmful to individuals, families, institutions, communities, and nations. It is commonly understood that human trafficking is a widespread problem, yet the variation in global estimates is extreme, ranging from 12.3 million to 20.9 million to 45.8 million people worldwide. The wide variation in estimates has led some to argue that claims about the scope of the problem are unsubstantiated. Calculating an estimate of human trafficking victims has proven to be complex; there is growing recognition that it is necessary to improve the methodologies used to generate such estimates. This article addresses the need for a better understanding of the methodologies used in human trafficking prevalence estimation studies. We conducted a comprehensive scoping review of prior human trafficking prevalence studies, including an analysis of the methodologies utilized and the context in which they were used, and offer a set of recommendations for future research on human trafficking prevalence. The goal of this effort is to provide guidance to researchers planning to undertake prevalence estimation studies and to help advance and improve human trafficking prevalence estimation research.
