Recent articles have raised important questions about the validity of prevalence data on human trafficking, exposing flawed methodologies behind frequently cited statistics. While considerable evidence points to the fact that human trafficking does exist in the United States and abroad, many sources of literature continue to cite flawed data and some misuse research in ways that seemingly inflate the problem, which can have serious implications for anti-trafficking efforts, including victim services and anti-trafficking legislation and policy. This systematic review reports on the prevalence data used in 42 recently published books on sex trafficking to determine the extent to which published books rely on data estimates and just how they use or misuse existing data. The findings from this review reveal that the vast majority of published books do rely on existing data that were not rigorously produced and therefore may be misleading or at minimum, inaccurate. Implications for practice, research, and policy are discussed, as well as recommendations for future prevalence studies on human trafficking.