The term "prison–industrial complex" (PIC), after the "military–industrial complex" of the 1950s, describes the attribution of the rapid expansion of the US inmate population to the political influence of private prison companies and businesses that supply goods and services to government prison agencies for profit. According to this concept the most common agents of PIC are corporations that contract cheap prison labor, construction companies, surveillance technology vendors, companies that operate prison food services and medical facilities, correctional officers unions, private probation companies, lawyers, and lobby groups that represent them.