Affiliation to voluntary insurance is voluntary, but once acquired becomes irrevocable, except if the insured becomes salaried, self employed, acquires the right to family benefit or is insured by the State. Because of the irrevocable character, it is not included in the voluntary category. According to data of the Centralized System Bursar (SICERE) of the Costa Rican Social Security Fund, in June 2015 there were 171.661 registered as voluntarily insured. This number represents about 3.55% of the national population. The voluntary insured is referred to students, housewives or other person with taxable capacity that do not perform an economic activity. http://www.oecd.org/els/health-systems/OECD-HSC-Survey-2016-CostaRica-Comments.pdf