Because of its hidden nature, it is difficult to determine the precise magnitude of the problem of trafficking in women. As is the case with other forms of violence against women, victims are often reluctant to report or make the fact of the violence known publicly. On the other hand, media reports frequently give estimates of numbers of women trafficked into the commercial sex industry for various regions and countries. Such statistics vary widely and are frequently unreliable or inaccurate. Furthermore, the methods by which such statistical data are gathered are seldom included, and statistics are generally not disaggregated by the sex of the victim.

The United States Department of State Trafficking in Persons Report for 2003 estimates that 800,000 to 900,000 people are trafficked across international borders annually.  According to the report, millions of people around the world live in situations of forced labor and commercial sexual exploitation. The United Nations Population Fund states that "[s]tatistics about trafficking are unreliable for a number of reasons, including the clandestine nature of the activity. However, rough estimates suggest that between 700,000 to 2 million women are trafficked across international borders annually. Adding domestic trafficking would bring the total much higher, to perhaps 4 million persons per year."