Under the current Constitution enacted in October 1988, elections are held every four years (except for the first one, which was held five years before the second to match the centenary of the Proclamation of the Republic) and citizens elect a ticket for both president and vice-president. Voting is mandatory for men and women between 18 and 70 years old who are not illiterate, and optional for people aged 16–17, over 70, and illiterates.