Traffickers are buying and selling hundreds of people in California, according to a report by the attorney general's office.
Attorney General Kamala Harris held a symposium on that topic on Friday.
In a report, the department gives its best estimates of the extent of these crimes. A task force identified 1,277 victims from mid 2010 to mid 2012 and arrested 1,798 suspects.
Contrary to popular perception, the report says, most of the victims seem to be American. Of those whose country of origin could be identified, 72% were born in the United States.
California differs from other regions, the researchers found. Worldwide, there are 3.5 times as many people sold for labor as for sex, but in California 56 percent of the victims were exploited for sex.