A sex worker is a person who provides sex work, either on a regular or occasional basis. The term is used in reference to those who work in all areas of the sex industry. According to one view, sex work is different from sexual exploitation, or the forcing of a person to commit sexual acts, in that sex work is voluntary "and is seen as the commercial exchange of sex for money or goods". In an attempt to further clarify the broad term "sex work", John E. Exner, an American psychologist, worked with his 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 (courtesans) 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 the family income, and Class V consists of 'streetwalker addicts', or 'drugs-for-sex streetwalkers' who are considered the lower class of the profession." Terminology The term "sex worker" was coined in 1978 by sex worker activist Carol Leigh. Its use became popularized after publication of the anthology, Sex Work: Writings By Women In The Sex Industry in 1987, edited by Frédérique Delacoste and Priscilla Alexander. The term "sex worker" has since spread into much wider use, including in academic publications, by NGOs and labor unions, and by governmental and intergovernmental agencies, such as the World Health Organization. The term is listed in the Oxford English Dictionary and Merriam-Webster's Dictionary. The term "sex worker" is used by some types of sex workers (i.e. prostitutes) to avoid invoking the stigma associated with the word "prostitute". Using the term "sex worker" rather than "prostitute" also allows more members of the sex industry to be represented and helps ensure that individuals who are actually prostitutes are not singled out and associated with the negative connotations of "prostitute". In addition, choosing to use the term "sex worker" rather than "prostitute" shows ownership over the individuals' career choices. Some argue that those who prefer the term "sex worker" wish to separate their occupation from their person. Describing someone