Skip to main content
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2020 Oct 1.
Published in final edited form as: Am J Public Health. 2019 Oct;109(10):1318–1319. doi: 10.2105/AJPH.2019.305258

Estimating the Prevalence of Human Trafficking: Progress Made and Future Directions

Julianna M Nemeth 1, Cynthia Fraga Rizo 2
PMCID: PMC6727304  NIHMSID: NIHMS1045375  PMID: 31483724

The Trafficking Victims Protection Act ( TVPA], 2000; P.L. 106–386) – a U.S. policy developed to combat human trafficking – defines human trafficking as “the recruitment, harboring, transportation, provision, or obtaining of a person for labor or services, through the use of force, fraud, or coercion for the purpose of subjection to involuntary servitude, peonage, debt bondage, or slavery.” Human trafficking, the term commonly used to refer to both labor and sex trafficking, is associated with negative physical, mental, and social outcomes (e.g., pain, depression, posttraumatic stress disorder, substance use).1 As such, practitioners, researchers and policymakers have been increasingly interested in understanding, preventing, and responding to this hidden epidemic.

A critical first step in addressing any problem is determining its presence. In their 2017 editorial for the American Journal of Public Health (AJPH), Rothman and colleagues (2017) identified key priorities for public health researchers to advance the field of anti-human trafficking, with the first priority being the more precise estimation of human trafficking.2 In the past few years, laudable efforts have been undertaken to develop innovative tools and methods to estimate human trafficking, and to determine the prevalence and incidence of human trafficking across the U.S., as well as specific states, counties, and sub-populations (e.g., immigrant laborers, homeless youth, child-welfare involved youth).3 As one example, Anderson, Kulig, and Sullivan recent study published in this issue of AJPH, “Estimating the Prevalence of Human Trafficking in Ohio 2014–2016,” focused on using existing systems-data from local child welfare, law enforcement, legal, and juvenile justice to determine estimates of known victims as well as those at-risk of trafficking in Ohio. Working through a process of integrating and triangulating existing data and removing duplication through probability matching across sets of data, the authors yielded a conservative count for human trafficking in Ohio—one that focused on sex trafficking primarily among girls.

Although strides have been made to develop and apply innovative methods to more accurately and reliably estimate the presence of human trafficking, the field continues to struggle with challenges to prevalence and incidence estimation given the complex nature of the problem and limits to data collected. In April 2019, the National Academies of Sciences, Engineering, and Medicine brought together experts in statistics, survey methodology, demography, public health, and human trafficking for a workshop on estimating the prevalence of human trafficking in the United States. Its focus was on presenting innovative methods that have been used to estimate the prevalence of human trafficking globally and in the U.S., as well as important definitional, measurement, methodological and ethical issues to estimating the prevalence of human trafficking.4 Innovative strategies presented in the workshop and discussed by Fedina and DeForge include adding human trafficking-related questions to national surveys using probability sampling (e.g., Youth Risk Behavior Surveillance System, National Agricultural Workers Survey) and epidemiologic methods using non-probably sampling with more sophisticated statistical weighting and corrections to corroborate prevalence and incident estimations. For instance, respondent driven sampling (RDS) holds promise for future prevalence estimation as it has been successfully used to estimate prevalence of sex and labor trafficking in prior studies—however, RDS studies can be costly.2

Capture-recapture methods may be a cost-saving alternative to RDS methods depending on the quality of existing data.4 Here in lies the issue--the systematic collection and recording of human trafficking data across geographic jurisdictions, systems and entities is lacking. Strategies used to estimate the prevalence of human trafficking by obtaining counts of known and/or potential victims from systems and community organizations rely on several assumptions. These include: (a) providers and employees are knowledgeable of human trafficking, including red flags and risk factors associated with victimization and perpetration; (b) systems and organizations use appropriate and validated instruments to screen for human trafficking or assess for indictors of human trafficking; and (c) human trafficking related data is documented consistently across systems and accessible to epidemiologists and researchers. Given this, we advocate the use of three strategies for enhancing efforts to more accurately identify victims of human trafficking and to estimate the prevalence of human trafficking in the population. These include: (1) consistently using a reliable screening measure of human trafficking in research and practice, (2) preparing systems, current community partners, as well as non-traditional community partners to incorporate human trafficking screening and documentation into standard practice, and (3) building the infrastructure necessary to deposit and cross-reference data sources from partners engaged in on-the-ground screening and work.

(1). Use Reliable Measures in Population-based Screening and Research

As Fedina and DeForge concluded, “both local and national studies need clearly defined measures of human trafficking (including the behaviors that comprise force, fraud, and coercion) to achieve more precise estimates of the population” (p.36).3 Although there has been progress in the development of screening and identification instruments for human trafficking, the research to evaluate measurement scale reliability and validity across different populations has not kept pace. This is a critically important first step in being able to compare human trafficking prevalence among sub-populations. Although further invariance testing across populations has yet to be done, a recently developed measure for use in homeless youth, which holds promise for use in other practice and research settings due to its brevity, is the Human Trafficking Screening Tool Short Form (HTST-SF). In six questions, the HTST-SF ascertains information about sex and labor trafficking by force, fraud or coercion.5

(2). Prepare Systems and Community Partners to Screen and Document Incidence

Traditional systems with the ability to identify survivors are likely under identifying victims—especially labor trafficking victims. Research suggests law enforcement, healthcare (e.g., hospital emergency departments), criminal justice (e.g., courts, jails, prisons, juvenile detention centers), child welfare, and homeless shelter professionals are not always knowledgeable about human trafficking or prepared to identify potential victims and perpetrators.6,7 Further, some victims may not come into contact with these systems or identify their experience as trafficking. For these reasons, it is critical that continued efforts are made to ensure that these systems and community organizations, as well as non-traditional partners, are trained to proactively screen for and identify human trafficking. Potentially promising non-traditional partners for identifying and routing people into services for labor and sex trafficking include industries (e.g., agriculture and construction), traditional/alternative public schools, and substance use treatment clinics.

(3). Build Infrastructure so that Data on Human Trafficking can be Compiled Across Sites

Finally, infrastructure needs to be developed within geographic regions to ensure that community partners engaged in screening and identifying trafficking victims have the opportunity to report essential items to a cross system depository. We need to ensure that systems and agencies are documenting data in similar ways for linking, de-duplicating, all while addressing privacy and confidentiality concerns. Consequently, this work will take investment of resources at the state or regional level to create the collaboration and infrastructure necessary to identity human trafficking victims, and provide the data necessary for more accurate prevalence estimations.

We are hopeful that there is rising considerations by practitioners, researchers, and government officials to document the gravity of human trafficking, and to understand the scope of this public health crisis--both to prevent and adequately support interventions designed to enhance survivor well-being.

References

  • 1.Oram S, Stoöckl H, Busza J, Howard LM, Zimmerman C. Prevalence and Risk of Violence and the Physical, Mental, and Sexual Health Problems Associated with Human Trafficking: Systematic Review. PLoS Medicine 2012;9(5). [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Rothman EF, Stoklosa H, Baldwin SB, et al. Public Health Research Priorities to Address US Human Trafficking. American Journal of Public Health 2017;107(7):1045–1047. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Fedina L, DeForge BR. Estimating the Trafficked Population: Public-Health Research Methodologies May Be the Answer. Journal of Human Trafficking 2017;3(1):21–38. [Google Scholar]
  • 4.The National Academies of Sciences, Engineering, and Medicine. Committee on National Statistics. Approaches to Estimating the Prevalence of Human Trafficking in the U.S. April 8–9, 2019 Workshop https://sites.nationalacademies.org/DBASSE/CNSTAT/estimating-the-prevalence-of-human-trafficking-in-the-us/index.htm. Accessed May 31, 2019.
  • 5.Dank ML, Yahner J, Yu L, et al. Pretesting a human trafficking screening tool in the child welfare and runaway and homeless youth systems 2017; https://www.urban.org/sites/default/files/publication/93596/pretesting_tool_0.pdf. Accessed May 19, 2019.
  • 6.McMahon-Howard J, Reimers B. An evaluation of a child welfare training program on the commercial sexual exploitation of children (CSEC). Evaluation and Program Planning 2013;40:1–9. [DOI] [PubMed] [Google Scholar]
  • 7.Renzetti CM, Bush A, Castellanos M, Hunt G. Does training make a difference? An evaluation of a specialized human trafficking training module for law enforcement officers. Journal of Crime and Justice 2015;38(3):334–350. [Google Scholar]

RESOURCES