NATIONAL INSTITUTE OF JUSTICE • JULY 2013 • NCJ 242955 PAGE 1

NATIONAL INSTITUTE OF JUSTICE

IN SHORT

U.S. Department of Justice

Office of Justice Programs

National Institute of Justice

Human trafficking has become big business, estimated to generate 

billions of dollars each year by entrapping and exploiting millions of 

people. But there is limited information and few hard numbers about 

trafficking: How many people are victims of trafficking? Who are 

they? Under what circumstances does trafficking occur?

Fully answering these questions is difficult, because victims of 

human traffickers are often unable or unwilling to come forward. But 

law enforcement and other officials cannot solve the problem until it 

is better understood. 

NIJ funded a study by researchers at San Diego State University to 

improve understanding about the nature and prevalence of labor 

trafficking. The study, Looking for a Hidden Population: Trafficking of 

Migrant Laborers in San Diego County, examines the experiences of 

826 unauthorized Spanish-speaking workers in San Diego County, 

Calif., and finds that a significant number — more than 30 percent 

— have experienced an incident that meets the legal definition of 

trafficking.1, 2

The study used a conservative — or narrow — interpretation of 

what constitutes trafficking, defining a trafficking violation as an 

act that involves restrictions imposed by employers on a worker’s 

physical or communicative freedom, and/or actual or threatened 

assaults to a worker’s physical body. Examples of labor trafficking 

violations include beatings, imprisonment and sexual abuse.

Modern-day slavery 

Human trafficking crimes, defined in Title 18, Chapter 

77, of the U.S. Code, involve the act of compelling or 

coercing a person’s labor, services or commercial sex 

acts. The statutes are rooted in the prohibition against 

slavery and involuntary servitude that is guaranteed by 

the 13th Amendment of the Constitution.

Thirty Percent of Migrant Laborers in San 

Diego Experience Trafficking Violations

The study also looked at practices that did not rise to the level of 

labor trafficking but that were fraudulent, deceptive or abusive. These 

included wage theft and instructing workers to lie about their own or 

their employer’s identity. A majority of the workers — 55 percent — 

were victims of abusive labor practices or gross exploitations.

Methods 

The study surveyed unauthorized, Spanish-speaking migrant 

laborers in San Diego County. The average age of the workers was 

33 years. Eighty-five percent of those surveyed had less than a 

junior high school education. Nearly all (98 percent) were Mexican. 

Fewer than 30 percent were proficient in English.

The participants were identified through social networks and with 

the help of an advocacy group that works closely with immigrants 

in the area. The workers answered a questionnaire about their 

experiences traveling to the U.S. and during their employment here. 
NATIONAL INSTITUTE OF JUSTICE • JULY 2013 • NCJ 242955 PAGE 2

Findings

Workers experienced most of the trafficking violations and abuses 

during their employment, rather than during their travel to the 

United States. Only 6 percent of those who traveled with the 

help of a smuggler (also called a coyote) experienced smugglerspecific trafficking violations, though approximately 20 percent did 

experience abuse at the hands of smugglers. 

Many more migrants — 28 percent — experienced labor trafficking 

at the hands of employers. Of that group, 15 percent reported that 

their physical integrity had been threatened and 22 percent reported 

physical restriction or deprivation at the workplace. Approximately 

49 percent experienced abusive labor practices at the hands of 

employers.

The report found that some sectors in which unauthorized migrant 

laborers are usually employed have higher rates of victimization 

than others. Agriculture had the lowest rate of victimization among 

all businesses. Construction, janitorial/cleaning and landscaping 

sectors had the highest rates of reported trafficking violations and 

labor abuses. See Exhibit 1.

The types of violations that unauthorized workers experienced also 

varied by occupation. For example, 20 percent of food processing 

workers reported threats to their physical integrity, compared with 

6 percent in manufacturing. Construction workers and those in 

janitorial and cleaning jobs reported higher levels of restriction and 

deprivation (27 percent in each group) than did those in agricultural 

work (12 percent). See Exhibit 2.

Workers who had minimal English language skills were the most 

likely to be victimized by employers.

Conclusions

The study shows that a substantial number of unauthorized, 

Spanish-speaking migrant laborers in San Diego have experienced 

labor trafficking violations and that even more have been the victims 

of fraudulent, deceptive or abusive labor practices.

Although it is unclear whether the findings would be similar for 

unauthorized workers in other parts of the country, the study 

suggests that labor trafficking violations and abusive labor practices 

may be common in areas where there is a large unauthorized 

workforce. Using the San Diego findings to roughly estimate 

national figures imply that there could be as many as 2.5 million 

labor trafficking victims just among unauthorized Spanish-speaking 

migrant laborers in the United States.

Actions

There is still much to be learned about labor trafficking in the U.S., 

but the study suggests the following steps:

• Direct resources to counter labor trafficking.

• Investigate and prosecute violators. 

• Develop a bridge between law enforcement and advocacy groups 

to build trust with migrant laborers.

• Create a public awareness campaign to include publicizing 

prosecutions and providing information on social services.

Exhibit 1. Percent of Workers 

Experiencing Trafficking or Abuse 

Occupation Labor Trafficking 

Violations, %

Abusive Labor 

Practices, %

Construction 35 63

Janitorial/

cleaning 36 59

Landscaping 27 60

Manufacturing 28 38

Food processing 32 51

Agriculture 16 27
NATIONAL INSTITUTE OF JUSTICE • JULY 2013 • NCJ 242955 PAGE 3

For More Information

• NIJ’s human trafficking topic page, http://nij.gov/topics/crime/

human-trafficking/welcome.htm.

• Maureen Q. McGough, “Ending Modern-Day Slavery: Using 

Research to Inform U.S. Anti-Human Trafficking Efforts,” NIJ 

Journal, http://www.nij.gov/nij/journals/271/anti-humantrafficking.htm.

Notes

1. Zhang, Sheldon X. Looking for a Hidden Population: Trafficking 

of Migrant Laborers in San Diego County. San Diego, CA: San 

Diego State University, 2012. Available at https://www.ncjrs.gov/

pdffiles1/nij/grants/240223.pdf.

2. There are three main frameworks that researchers in the U.S. 

usually use to define labor trafficking activities: the United 

Nations Protocol to Prevent, Suppress, and Punish Trafficking in 

Persons; the International Labor Organization definition; and the 

Victims of Trafficking and Violence Protection Act of 2000. The 

study attempted to synthesize these three definitions, although 

the questionnaire aligns most closely with the U.S. government’s 

definition.

Exhibit 2. Percent of Violations by Type and Occupation 

Occupation Threats to Physical 

Integrity, %

Restriction/

Deprivation, % Deception/Lies, % Abusive/Exploitative Practices, %

Agriculture 10 12 11 25

Construction 17 27 37 57

Landscaping 16 24 20 56

Janitorial/cleaning 17 27 43 55

Food processing 20 24 26 49

Manufacturing 6 23 26 31
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*NCJ~242955*