The structure of the Swiss militia system stipulates that the soldiers keep their own personal equipment, including all personally assigned weapons, at home (until 2007 this also included ammunition[3]). Compulsory military service concerns all male Swiss citizens, with women serving voluntarily. Males usually receive initial orders at the age of 18 for military conscription eligibility screening. About two-thirds of young Swiss men are found suitable for service, while alternative service exists for those found unsuitable.[4] Annually, approximately 20,000 persons are trained in basic training for a duration from 18 to 21 weeks (increased from 15 weeks, in 2003).