Private detectives assist in investigations prompted by individuals, businesses, and law firms, usually in order to gather evidence regarding legal proceedings, background investigations, missing persons cases, insurance fraud, or marital infidelity. Education for private detectives varies, and many have backgrounds in professional law enforcement or criminal justice related careers before becoming private investigators. Licensing requirements for private detectives varies by state. In 2006 about one-third of private investigators were self-employed, one third worked for private detective agencies, and the remaining third for either government or private companies. Employment for private detectives is expected to increase by 18 percent by the year 2016.