Prostitution is the business or practice of engaging in sexual activity in exchange for payment. Prostitution is sometimes described as sexual services, commercial sex or, colloquially, hooking. It is sometimes referred to euphemistically as the world's oldest profession in the English-speaking world. A person who works in this field is called a prostitute and is a type of sex worker. Prostitution occurs in a variety of forms, and its legal status varies from country to country (sometimes from region to region within a given country), ranging from being an enforced or unenforced crime, to unregulated, to a regulated profession. It is one branch of the sex industry, along with pornography, stripping, and erotic dancing. Brothels are establishments specifically dedicated to prostitution. In escort prostitution, the act may take place at the client's residence or hotel room (referred to as out-call), or at the escort's residence or a hotel room rented for the occasion by the escort (in-call). Another form is street prostitution. There are about 42 million prostitutes in the world, living all over the world (though most of Central Asia, the Middle East and Africa lacks data, studied countries in that large region rank as top sex tourism destinations). Estimates place the annual revenue generated by prostitution worldwide to be over [dollar]100 billion.The majority of prostitutes are female and have male clients. The position of prostitution and the law varies widely worldwide, reflecting differing opinions. Some view prostitution as a form of exploitation of or violence against women, and children, that helps to create a supply of victims for human trafficking. Some critics of prostitution as an institution are supporters of the Nordic model, which decriminalizes the act of selling sex, but makes the purchase of sex illegal. This approach has also been adopted by Canada, Iceland, Ireland, Northern Ireland, Norway, and France. Others view sex work as a legitimate occupation, whereby a person trades or exchanges sexual acts for money. Amnesty International is one of the notable groups calling for the decriminalization of prostitution.