A Systematic Review of Statistical Analytical Methods Used in Global Human Trafficking Research

Background: Human Trafficking is a global problem and a serious crime against humanity. The 2017 report of International Labor Organization (ILO) reported globally 40.3 million people had fallen victims of human trafficking in 2016. According to global counter trafficking database of International Organization for Migration (IOM), each year at least 5000 new cases of human trafficking get added to their database. Research on trafficking and trafficking related issues is one way to address this phenomenon. Previous work reported social work students lack research skills, particularly quantitative research method skills. This study attempts to review and synthesize global literature on human trafficking with a focus on quantitative statistical analysis at use in human trafficking research. The aim of this study is to disseminate gathered knowledge about statistical methods to inform the students and scholars of the social work field.

Method: This study was conducted following PRISMA framework. Social Work Abstracts, Social Services Abstracts, SociaIndex, PsycINFO, Sociological Abstracts, and PubMed were searched for pertinent literatures. Search terms used for literature search included "human traffick*" OR "sex traffick*" OR " Labor traffick*" OR "trafficked persons" OR " Child traffick*" OR " Youth traffick*". Inclusion criteria for full text review of the pertinent articles included (1) any study that used quantitative methods, (2) studies where participants were identified as survivors or victims of human trafficking, (3) peer reviewed articles, (4) articles published in English between the period of January 1, 2000, and September 30, 2021. Electronic searches identified total 6174 articles. After eliminating duplicate articles and initial screening by title and abstract 36 articles remained. Upon full text review of the 36 articles based on inclusion exclusion criteria, 18 articles were retained.

Result: Included studies for this study were conducted in 18 countries of the world. The sample size of these studies ranges from 66 to 1387. Study participants included both male (n= 2510) and female (n= 3354) victims or survivors of human trafficking that vary in age from childhood-adulthood. One of the notable facts is, the least utilized source of data was secondary dataset or official statistics This study found variation in the statistical analytical methods used in these studies, while regression is the most frequently used method in these studies (n = 13).

Discussion: Knowledge about statistical analytical methods can result in well-designed studies that provide reliable and valid data, and lead to increase generalizability of outcomes. The findings of this review can help researchers to identify strengths and weakness of the different statistical analytical methods used with human trafficking. Findings will also help ensure the application of statistical method for accurately predicting causal relationships among variables as well as for correct interpretation of results. One of the noticeable facts in trafficking research is biased data collection as participants who are in the post victimization state are most likely to be recruited as participants. Human trafficking research needs to apply more relevant sampling and recruitment methods that have been used by other disciplines on hidden and transient population to address this issue.