Electoral system
Electoral rules place limits on suffrage and candidacy. Most countries's electorates are characterised by universal suffrage, but there are differences on the age at which people are allowed to vote, with the youngest being 16 and the oldest 21 (although voters must be 25 to vote in Senate elections in Italy). People may be disenfranchised for a range of reasons, such as being a serving prisoner, being declared bankrupt, having committed certain crimes or being a serving member of the armed forces. Similar limits are placed on candidacy (also known as passive suffrage), and in many cases the age limit for candidates is higher than the voting age. A total of 21 countries have compulsory voting, although in some there is an upper age limit on enforcement of the law. Many countries also have the none of the above option on their ballot papers.
Voting age
Eighteen is the most common voting age, with a small minority of countries differing from this rule. Those with a national minimum age of 17 include East Timor, Greece, Indonesia, North Korea, South Sudan and Sudan. The minimum age is 16 in Argentina, Austria, Brazil, Cuba, Ecuador, Nicaragua and the Isle of Man, Jersey and Guernsey (three self-governing British Crown Dependencies). People aged 16–18 can vote in Bosnia, Serbia and Montenegro if employed. The highest minimum voting age is 21 in several nations. Some countries have variable provision for the minimum voting age, whereby a lower age is set for eligibility to vote in state, regional or municipal elections.