PR can only be used in multi-member electorates. Candidates are elected in proportion to the number of votes they receive which increases the chances of representation for small minority parties.

The proportion of seats won by each group or party should equal the proportion of votes cast for those groups or parties. For example, if a party wins 40% of the votes, it should win about 40% of the seats and if a party gets 10% of the votes it should gain 10% of the seats.

In some jurisdictions group voting squares are used. Electors may number group voting squares in order of preference 'above the line' on the ballot paper. This records a vote for the first candidate in the group with preferences going to the other candidates in the order in which they are listed and then to the next group if indicated. The alternative is marking squares 'below the line' in order of preference for individual candidates.

PR is used in Australia for the:

• NSW local government elections where three or more vacancies exist in an area/ward
• Legislative Councils (Upper Houses) of NSW, Victoria, South Australia and Western Australia
• Australian Capital Territory Legislative Assembly
• Lower House of Tasmania
• the Australian Senate.

PR is widely used in South America and Western Europe, and makes up about one-third of all systems in Africa.

List proportional representation (List PR)

Most PR systems use some form of List PR. List PR is used in multi-member electorates where votes are cast in order of preference for the parties which have registered a list of candidates. Parties receive seats in proportion to their overall share of the total vote and winning candidates are taken from the lists in order of their position.

Mixed member proportional (MMP)

MMP systems try to combine the elements of majority and PR systems. A proportion of the parliament is elected by majority methods, usually from single-member electorates, while the remainder come from PR Lists.

Under MMP systems, the List PR seats compensate for any disproportions produced by the district seat results. For example, if one party wins 10% of the national votes but no district seats, they would be awarded enough seats from the PR lists to bring their representation up to around 10% of the parliament.

MMP is used in countries such as Germany, New Zealand, Italy and Venezuela.

The single transferable vote (STV)

The STV system is used in multi-member districts with electors ranking candidates in order of preference on the ballot paper as in PV. Preference marking is usually optional where electors can mark as many candidates as they choose. After the total number of 1st preference votes is added up, the count begins by establishing the quota of votes needed for the election of a single candidate. The quota calculation is:

The 1st stage determines the total number of 1st preference votes per candidate. Any candidate who has more 1st preferences than the quota is immediately elected. Their surplus votes are redistributed at a fractional percentage of one vote, so that the total redistributed votes equals the candidate’s surplus. For example, if a candidate had 100 votes, and their surplus was ten, each ballot paper would be redistributed at one-tenth of a vote.

If no one has achieved the quota, the candidate with the lowest number of 1st preferences is eliminated, with their 2nd preferences redistributed to the candidates left in the race. This process continues until all seats are filled.

All Australian PR systems use the STV, although the South Australian, Victorian, Western Australian and NSW Upper Houses and the federal Senate may be thought of as semi-list systems as the ballot paper also provides for group voting above the line or in the case of Western Australia left and right of the line.

STV is used for national parliamentary elections in Ireland, Malta and Estonia.