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.
Compulsory voting
Supporters of compulsory voting also argue that voting addresses the paradox of voting, which is that for a rational, self-interested voter, the costs of voting will normally exceed the expected benefits. The paradox disproportionately affects the socially disadvantaged, for whom the costs of voting tend to be greater. Australian academic and supporter of compulsory voting, Lisa Hill, has argued that a prisoner's dilemma situation arises under voluntary systems for marginalised citizens: it seems rational for them to abstain from voting, under the assumption that others in their situation are also doing so, in order to conserve their limited resources. However, since these are people who have a pronounced need for representation, this decision is irrational. Hill argues that the introduction of compulsory voting removes this dilemma.