For example, one study of sex work in Tijuana, Mexico found that the majority of sex workers there are young, female and heterosexual.Many of these studies attempt to use smaller samples of sex workers and pimps in order to extrapolate about larger populations of sex workers.
Exner, an American psychologist, worked with his fellow colleagues to create five distinct classes for categorizing sex workers.
One scholarly article details the classes as follows: "specifically, the authors articulated Class I, or the upper class of the profession, consisting of call girls; Class II was referred to as the middle class, consisting of 'in-house girls' who typically work in an establishment on a commission basis; Class III, the lower middle class, were 'streetwalkers' whose fees and place of work fluctuate considerably; Class IV sex workers have been known as 'commuter housewives', and they are typically involved in sex work to supplement family income; and Class V consists of 'streetwalker addicts', or 'drugs-for-sex streetwalkers' who are considered the lower class of the profession." The term sex worker was coined in 1978 by sex worker activist Carol Leigh.
One report on the underground sex trade in the United States used known data on the illegal drug and weapon trades and interviews with sex workers and pimps in order to draw conclusions about the number of sex workers in eight American cities.
However, studies like this one can come under scrutiny for a perceived emphasis on the activities and perspectives of pimps rather than those of sex workers themselves.
Sexual empowerment is another possible reasons why people engage in sex work.
One study found that a majority of the sex workers interviewed enjoyed their occupation and felt like they were discovering themselves.
Sex workers may be any gender and exchange sexual services or favors for money or other gifts.
The motives of sex workers vary widely and can include debt, coercion, survival, or simply as a way to earn a living.
Some argue that those who prefer the term sex worker wish to separate their occupation from their person.
Describing someone as a sex worker recognizes that the individual may have many different facets, and are not necessarily defined by their job.
Maintaining privacy and confidentiality in research is also difficult because many sex workers may face prosecution and other consequences if their identities are revealed.