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. Under other election systems, a bare plurality or a scant majority are all that are used to elect candidates. Further, a PR system is one that produces mixed and balanced representation, reflecting how votes are cast.
Party-list proportional representation (list-PR) is a system of proportional representation based on preregistered political parties, with each party being allocated a certain number of seats roughly proportional to their share of the vote.
The additional-member system (AMS) or is a mixed electoral system under which most representatives are elected in single-member districts (SMDs), and a fixed number of 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.
Mixed-member proportional representation is a mixed electoral system which combines local winner-take-all 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 typical 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.
Overhang seats are constituency seats won in an election under the traditional mixed-member proportional (MMP) system, when a party's share of the nationwide votes would entitle it to fewer seats than the number of individual constituencies won. The electoral reform in Germany removed the overhang seats, and replaced with Zweitstimmendeckung.
First-preference plurality (FPP)—often shortened simply to plurality—is a single-winner system of positional voting where voters mark one candidate as their favorite, and the candidate with the largest number of points is elected. It is also called first-past-the-post (FPTP), based on a metaphor from horse racing.
In political science, parallelvoting or superposition refers to the use of two or more electoral systems to elect different members of a legislature. More precisely, an electoral system is a superposition if it is a mixture of at least two tiers, which do not interact with each other in any way; one part of a legislature is elected using one method, while another part is elected using a different method, with all voters participating in both. Thus, the final results can be found by calculating the results for each system separately based on the votes alone, then adding them together. A system is called fusion or majority bonus, another independent mixture of two system but without two tiers. Superposition is also not the same as "coexistence", which when different districts in the same election use different systems. Superposition, fusion and coexistence are distinct from dependent mixed electoral systems like compensatory (corrective) and conditional systems.
A referendum was held on October 10, 2007, on the question of whether to establish a mixed member proportional representation (MMP) system for elections to the Legislative Assembly of Ontario. The vote was strongly in favour of the existing plurality voting or first-past-the-post (FPTP) system.
A party-list system is a type of electoral system that formally involves political parties in the electoral process, usually to facilitate multi-winner elections. In party-list systems, parties put forward a list of candidates, the party-list who stand for election on one ticket. Voters can usually vote directly for the party-list, but in other systems voters may vote for directly individuals candidates within or across party lists, besides or instead of voting directly for parties.
Scotland uses different electoral systems for elections to Parliament, the Scottish Parliament and to local councils. A different system was also in use between 1999 and 2019 for United Kingdom elections to the European Parliament. Historically, only First Past the Post (FPTP) was used for all elections in Scotland, but this changed in 1999 both with the introduction of D'Hondt elections to the EU Parliament and the inception the same year of the devolved Scottish Parliament. Two of the devolved legislatures in the United Kingdom - the Scottish Parliament and the Senedd - use the Additional Members System (AMS). AMS has been used for every Scottish Parliament election since 1999, with the most recent being in 2021.
Electoral reform is a change in electoral systems which alters how public desires are expressed in election results.
Semi-proportional representation characterizes multi-winner electoral systems which allow representation of minorities, but are not intended to reflect the strength of the competing political forces in close proportion to the votes they receive. Semi-proportional voting systems are generally used as a compromise between complex and expensive but more-proportional systems and simple winner-take-all systems. Examples of semi-proportional systems include the single non-transferable vote, limited voting, and parallel voting.
An electoral 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.
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 in theory. However, the design proved susceptible to the decoy list strategy, and as a result by 2001 had devolved into a de facto parallel voting system. The method is only known to have been used in Italy and for a portion of the compensatory tier of the National Assembly of Hungary.
Dual-member proportional representation (DMP), also known as dual-member mixed proportional, is an electoral system designed to produce proportional election results across a region by electing two representatives in each of the region’s districts. The first seat in every district is awarded to the candidate who receives the most votes, similar to first-past-the-post voting (FPTP). The second seat is awarded to one of the remaining district candidates so that proportionality is achieved across the region, using a calculation that aims to award parties their seats in the districts where they had their strongest performances.
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.
Rural–urban proportional representation (RUP), also called flexible district PR, is a mixed electoral system which combines the use of single- and multi-member constituencies in a lower tier and top-up seats in an upper tier to meet the different needs of both rural and urban areas, while protecting the objective of proportionality. The term was coined by Fair Vote Canada, which devised a rural–urban system with the intention of meeting the special challenges of Canada's geography, which includes wide-flung, sparsely populated areas.
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.
The mixed ballot transferable vote (MBTV) refers to a type of vote linkage-based mixed-member electoral system where a group of members are elected on local (lower) tier, for example in single-member districts (SMDs). Other members are elected on a compensatory national (upper) tier from a list and voters cast a single ballot where they may indicate their preferences separately.
Mixed-member majoritarian representation (MMM) is type of a mixed electoral system combining winner-take-all and proportional methods, where the disproportional results of the winner-take-all part are dominant over the proportional component. Mixed member majoritarian systems are therefore categorized under semi-proportional representation, and are usually contrasted with mixed-member proportional representation (MMP) which aims to provide proportional representation compensation ("top-up") seats.
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