Prostitution or sex work in Australia is governed by state and territory laws, which vary considerably. Federal legislation also affects some aspects of sex work throughout Australia, and of Australian citizens abroad. The United Nations Programme on HIV and AIDS (UNAIDS), which issues regular statistics on sex work, estimated there were around 20,500 sex workers in Australia in 2016. Scarlet Alliance, a national peer sex worker NGO, provides advocacy for sex workers in Australia.