Proportional representation (PR) refers to any type of electoral system under which subgroups of an electorate are reflected proportionately in the elected body. The concept applies mainly to political divisions among voters. The essence of such systems is that all votes cast – or almost all votes cast – contribute to the result and are effectively used to help elect someone – not just a bare plurality or (exclusively) the majority – and that the system produces mixed, balanced representation reflecting how votes are cast.
Party-list proportional representation (list-PR) is a subset of proportional representation electoral systems in which multiple candidates are elected through their position on an electoral list. They can also be used as part of mixed-member electoral systems.
The single transferable vote (STV), sometimes known as proportional ranked choice voting (P-RCV), is a multi-winner electoral system in which each voter casts a single vote in the form of a ranked-choice ballot. Voters have the option to rank candidates, and their vote may be transferred according to alternate preferences if their preferred candidate is eliminated or elected with surplus votes, so that their vote is used to elect someone they prefer over others in the running. STV aims to approach proportional representation based on votes cast in the district where it is used, so that each vote is worth about the same as another.
The additional-member system (AMS) is a mixed electoral system under which most representatives are elected in single-member districts (SMDs), and the other "additional members" are elected to make the seat distribution in the chamber more proportional to the way votes are cast for party lists. It is distinct from parallel voting in that the "additional member" seats are awarded to parties taking into account seats won in SMDs, which is not done under parallel voting.
In the study of electoral systems, the Droop quota is the minimum number of votes needed for a party or candidate to guarantee they will win at least one seat in a legislature.
Mixed-member proportional representation is a mixed electoral system which combines local majoritarian elections with a compensatory tier of party list votes, which are used to allocate additional members in a way that aims to produce proportional representation overall. In most MMP systems, voters get two votes: one to decide the representative for their single-seat constituency, and one for a political party. Some countries use single vote variants of MMP, although this article focuses primarily on dual vote versions of MMP.
Parallel voting is a type of mixed electoral system in which representatives are voted into a single chamber using two or more different systems, most often first-past-the-post voting (FPTP) with party-list proportional representation (PR). It is the most common form of mixed member majoritarian representation (MMM), which is why these terms are often used synonymously with each other. In some countries, parallel voting is known as the supplementary member (SM) system, while in academic literature it is sometimes called the superposition method within mixed systems.
An electoral district, also known as an election district, legislative district, voting district, constituency, riding, ward, division, electorate, or (election) precinct, is a subdivision of a larger state created to provide its population with representation in the larger state's constituency. That body, or the state's constitution or a body established for that purpose, determines each district's boundaries and whether each will be represented by a single member or multiple members. Generally, only voters (constituents) who reside within the district are permitted to vote in an election held there. District representatives may be elected by a first-past-the-post system, a proportional representative system, or another voting method. They may be selected by a direct election under universal suffrage, an indirect election, or another form of suffrage.
The Imperiali quota or pseudoquota is an inadmissible electoral quota used to calculate the number of votes needed to earn a seat in single transferable vote or largest remainder elections. It is named after Belgian senator Pierre Imperiali.
In the study of apportionment, the Harequota is the number of voters represented by each legislator under a system of proportional representation. In these voting systems, the quota is the number of votes that guarantees a candidate, or a party in some cases, captures a seat. The Hare quota is the total number of votes divided by the number of seats to be filled.
There are a number of complications and issues surrounding the application and use of single transferable vote proportional representation that form the basis of discussions between its advocates and detractors.
Schulze STV is a draft single transferable vote (STV) ranked voting system designed to achieve proportional representation. It was invented by Markus Schulze, who developed the Schulze method for resolving ties using a Condorcet method. Schulze STV is similar to CPO-STV in that it compares possible winning candidate pairs and selects the Condorcet winner. It is not used in parliamentary elections.
In elections that use the single transferable vote (STV) method, quotas are used (a) for the determination of candidates considered elected; and (b) for the calculation of surplus votes to be redistributed. Two quotas in common use are the Hare quota and the Droop quota. The largest remainder method of party-list proportional representation can also use Hare quotas or Droop quotas.
An electoral system or voting system is a set of rules that determine how elections and referendums are conducted and how their results are determined. Electoral systems are used in politics to elect governments, while non-political elections may take place in business, non-profit organisations and informal organisations. These rules govern all aspects of the voting process: when elections occur, who is allowed to vote, who can stand as a candidate, how ballots are marked and cast, how the ballots are counted, how votes translate into the election outcome, limits on campaign spending, and other factors that can affect the result. Political electoral systems are defined by constitutions and electoral laws, are typically conducted by election commissions, and can use multiple types of elections for different offices.
A winner-take-all electoral system is one where a voting block can win all seats in a legislature or electoral district, denying representation to any political minorities. When applied using multiple electoral districts to elect an assembly, winner-take-all system provide non-proportional results that us: these systems often allow for electoral inversions, and they do not require candidates to win an (absolute) majority of the vote to be elected. A less-common but more accurate term is majorizing or majorized representation.
Scorporo is a partially compensatory, mixed-member majoritarian electoral system, sometimes referred to as a negative vote transfer system (NVT) whereby a portion of members are elected in single-member districts (SMDs) and a portion are elected from a list. It may be fully defined as a parallel voting system which excludes a portion of the SMD winners' votes in electing the proportional tier, to result in a more proportional outcome. The exclusion of a portion of the SMD winners' votes is what makes scorporo fundamentally different from parallel voting and somewhat closer to mixed member proportional representation, and thereby between the two in terms of proportionality. The system is only known to have been used in Italy and for a portion of the compensatory tier of the National Assembly of Hungary.
A mixed electoral system or mixed-member electoral system combines methods of majoritarian and proportional representation (PR). The majoritarian component is usually first-past-the-post voting (FPTP/SMP), whereas the proportional component is most often based on party-list PR. The results of the combination may be mixed-member proportional (MMP), where the overall results of the elections are proportional, or mixed-member majoritarian, in which case the overall results are semi-proportional, retaining disproportionalities from the majoritarian component.
Apportionment in the Hellenic Parliament refers to those provisions of the Greek electoral law relating to the distribution of Greece's 300 parliamentary seats to the parliamentary constituencies, as well as to the method of seat allocation in Greek legislative elections for the various political parties. The electoral law was codified for the first time through a 2012 Presidential Decree. Articles 1, 2, and 3 deal with how the parliamentary seats are allocated to the various constituencies, while articles 99 and 100 legislate the method of parliamentary apportionment for political parties in an election. In both cases, Greece uses the largest remainder method.
The mixed single vote (MSV) or positive vote transfer system (PVT) is a mixed-member electoral system, where voters cast a single vote in an election, which used both for electing a local candidate and as a vote for a party affiliated with that candidate according to the rules of the electoral system. Unlike the more widespread mixed proportional and mixed majoritarian systems where voters cast two votes, split-ticket voting is not possible in MSV.
Mixed member majoritarian representation (MMM) is type of a mixed electoral system combining majoritarian and proportional methods, where the disproportional results of district contests using a plurality voting system or other, usually first-past-the-post voting, are completely separate from the proportional component. Mixed member majoritarian systems are therefore described as semi-proportional representation, and are usually contrasted with mixed-member proportional representation (MMP) which aims to provide proportional representation via additional compensation ("top-up") seats.
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