Mixed-member proportional representation in the context of "Mixed electoral system"

In political science, parallel voting 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 portion of a legislature is elected using one method, while another portion is elected using a different method, with all voters participating in both. Thus, the final results are produced by filling the seats using each system separately based on the votes, then adding the two sets of results together.

A system is called fusion (not to be confused with electoral fusion) or majority bonus, if it is an independent mixture of two system without two tiers. Superposition (parallel voting) is also not the same as "coexistence", in which 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.

As a result of the first periodical review of Scottish Parliament constituencies, new constituencies and additional member regions of the Scottish Parliament were introduced for the 2011 Scottish Parliament election. The D'Hondt method is used, as previously, in the allocation of additional member seats. These boundaries were also used for the 2016 Scottish Parliament election and 2021 Scottish Parliament election; following the Second periodic review of Scottish Parliament boundaries which published its report in 2025, new boundaries will be used for the 2026 Scottish Parliament election.

The Scottish Parliament (Constituencies) Act 2004 required the Boundary Commission for Scotland to review boundaries of all constituencies except Orkney and Shetland (which cover, respectively, the Orkney Islands council area and the Shetland Islands council area) so that the area covered by the reviewed constituencies continues to be covered by a total of 71 constituencies. The Orkney and Shetland constituencies were taken into account, however, in review of boundaries of the additional member regions. The Commission began the review as announced on 3 July 2007, and provisional proposals were published on Thursday 14 February 2008. Final recommendations followed public consultations and a series of local inquiries, and the terms of the 2004 act required final recommendations to be submitted in a report to the Secretary of State for Scotland not later than 30 June 2010.

The Bundestag (German: [ˈbʊndəstaːk] , "Federal Diet") is the federal parliament of Germany. It is the only constitutional body in the country directly elected by the German people. The Bundestag was established by Title III of the Basic Law for the Federal Republic of Germany (Grundgesetz) in 1949 as one of the legislative bodies of Germany, the other being the Bundesrat.

The members of the Bundestag are representatives of the German people as a whole, are not bound by any orders or instructions and are only accountable to their conscience. Since the current 21st legislative period, the Bundestag has a fixed number of 630 members. The Bundestag is elected every four years by German citizens aged 18 and older. Elections use a mixed-member proportional representation system which combines first-past-the-post voting for constituency-seats with proportional representation to ensure its composition mirrors the national popular vote. The German Bundestag cannot dissolve itself; only the president of Germany can do so under certain conditions.

A mixed single vote (MSV) is a type of ballot in mixed-member electoral systems, where voters cast a single vote in an election, which is 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 most mixed proportional and mixed majoritarian systems (such as parallel voting) where voters cast two votes, split-ticket voting is not possible under MSV. This significantly reduces the possibility of manipulating compensatory mixed systems, at the price of reducing voter choice. An alternative based on the mixed single vote that still allows for indicating different preferences on different levels is the mixed ballot, which functions as a preferential (mixed) single vote.

With MSV, voters usually cast their single vote for a local candidate in a single-member district (SMD) and then all votes (or just the wasted votes, depending on the system) from this lower tier are added to distribute seats between upper tier candidates, typically national party lists. How proportional the outcome is depends on many factors including the vote transfer rules (which votes are recounted as party list votes), whether there is a seat linkage, and other parameters (e.g. the number of list seats) used in the system. MSV systems originate from Germany and variations are currently used in Bolivia, Lesotho and Hungary for local elections in larger municipalities.

The additional-member system (AMS) is a two-vote seat-linkage-based mixed electoral system used for elections to the Scottish Parliament in the United Kingdom, although not for Westminster elections, in which most representatives are elected in single-member districts (SMDs), and a fixed number of other "additional members" are elected from a closed list to make the seat distribution in the chamber more proportional to the votes cast for party lists. It is a form of mixed-member proportional representation and is distinct from using parallel voting for the list seats (also known as the supplementary-member system) in that the "additional member" seats are awarded to parties taking into account seats won in SMDs (referred to as compensation or top-up) – these are ignored under parallel voting, which is a non-compensatory method.

AMS is the name given to a particular system used in the United Kingdom that aims to provide proportional representation. However, in theory it can fail to be proportional. This is commonly caused by dis-proportional district results caused by seat overhang. The proportionality of AMS depends on having enough additional ("top-up") seats and on how votes are cast in a specific election. During its use in the United Kingdom, AMS produced results closer to mixed-member proportional rather than mixed-member majoritarian representation.

The Scottish Parliament (Holyrood), created by the Scotland Act 1998, has used a system of constituencies and electoral regions since the first general election in 1999.

The parliament has 73 constituencies, each electing one Member of the Scottish Parliament (MSP) by the plurality (first-past-the-post) system of voting, and eight additional member regions, each electing seven additional MSPs. Each region is a group of constituencies, and the D'Hondt method of allocating additional member seats from party lists is used to produce a form of proportional representation for each region. The total number of parliamentary seats is 129. For lists of MSPs, see Member of the Scottish Parliament.