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Social choice and electoral systems |
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Mathematicsportal |
The vote linkage [1] [2] [3] [4] or (multi-tier) vote transfer system [5] is type of compensatory mixed electoral system, where votes may be transferred across multiple tiers of an electoral system, in order to avoid wasted votes - in contrast to the more common seat linkage compensatory system (commonly referred to as MMP). [6] It often presupposes and is related to the concept of the mixed single vote, which means that the same vote can be used in multiple tiers of an electoral system and that a vote for a local candidate may automatically count as a vote for the candidate's party or the other way around [note 1] . Voters usually cast their single vote for a local candidate in a single-member district (SMD) and then all the wasted votes from this lower tier are added to distribute seats between upper tier candidates, typically national party lists.
Partially compensatory multi-tier vote linkage [7] [8] is an equivalent of the indirect single transferable vote among multi-tiered electoral systems (except for the mixed ballot transferable vote versions, which are multi-tier equivalents to STV). A related concept is seat linkage, where it is not the votes used in one tier that connect two tiers, but the number of seats a party achieved on the lower tier that is taken into account. A vote linkage system, when applied in a compensatory way takes into account the number of votes that were effective or wasted in the lower tier and takes this into account in the apportionment of the upper tier.
Vote linkage systems currently or formerly used for various national or local elections in Germany, Hungary and Italy have been sometimes described as mixed-majoritarian [7] [8] (similar to common versions of parallel voting), or a unique system between MMM and MMP (seat linkage). Some supermixed systems use vote linkage together with parallel voting (superposition) in a two-vote setup, where split ticket voting is allowed. [4] [9] How proportional the outcome depends on many factors including the vote transfer rules, such which votes are recounted as party list votes, and other parameters (e.g. the number of list seats) used in the system. [5] The vote linkage system originates from Germany and is currently used in Hungary. A version called scorporo was also used in Italy from 1993 to 2005. [2]
Party | Popular vote | District results | Without winner compensation | With winner compensation | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Transfer votes | Seats | Transfer votes | Seats | |||||||||||||
Party A strongholds (40) | Party B strongholds (20) | Seats | Party A strongholds (40) | Party B strongholds (20) | Total | List tier | Total | Party A strongholds (40) | Party B strongholds (20) | Total | List tier | Total | ||||
Party A | 41% | 45% | 33% | 40 | - | 33% | 11% | 8 | 48 | 20% | 33% | 24% | 13 | 53 | ||
Party B | 30% | 25% | 40% | 20 | 25% | - | 17% | 12 | 32 | 25% | 7% | 19% | 11 | 31 | ||
Party C | 25% | 25% | 25% | 0 | 25% | 25% | 25% | 17 | 17 | 25% | 25% | 25% | 14 | 14 | ||
Party D | 4% | 5% | 2% | 0 | 5% | 2% | 4% | 3 | 3 | 5% | 2% | 4% | 2 | 2 | ||
TOTAL | 100% | 100% | 100% | 60 | 55% | 60% | 57% | 40 | 100 | 75% | 67% | 72% | 40 | 100 |
Party | Popular vote | District results | Seats under parallel voting - no compensation | Vote transfer system without winner compensation | Vote transfer system with winner compensation | Seats under single vote seat linkage compensation | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Party A strongholds | Party B strongholds | Seats | List tier | Total | List tier | Total | List tier | Total | List tier | Total | ||||
Party A | 41% | 45% | 33% | 40 | 16 | 56 | 8 | 48 | 13 | 53 | 1 | 41 | ||
Party B | 30% | 25% | 40% | 20 | 12 | 32 | 12 | 32 | 11 | 31 | 10 | 30 | ||
Party C | 25% | 25% | 25% | 0 | 10 | 10 | 17 | 17 | 14 | 14 | 25 | 25 | ||
Party D | 4% | 5% | 2% | 0 | 2 | 2 | 3 | 3 | 2 | 2 | 6 | 6 | ||
TOTAL | 100% | 100% | 100% | 100 | 40 | 100 | 40 | 100 | 40 | 100 | 40 | 100 |
Mixed single vote systems may use vote linkage compensation, meaning not all, but only 'wasted' votes get transferred as list votes to the other tier. Some uncommon, supermixed [10] systems use of MSV may add or subtract the discounted list results to establish a vote linkage based element of compensation into system that would otherwise be categorised as parallel voting. Either type of system is misleadingly known in Hungarian as a "fractional vote recounting system" (Hungarian: töredékszavat-visszaszámláló rendszer), however, there are no fractional votes used in any variation, the name merely alluding to only a fraction of votes being "recounted" as list votes.
The third type of mixed single vote system is the single vote equivalent of parallel voting (sometimes called direct vote transfer [11] ), which uses the same vote on both the majoritarian and proportional tiers. This makes such systems non-compensatory, falling under the superposition type of mixed systems identified by Massicotte & Blais. [10]
Compensatory mixed systems | ||
---|---|---|
single vote systems (mixed single vote) | dual vote systems | |
Seat linkage | Single vote seat linkage MMP (top-up MSV) | Seat linkage two vote MMP: |
Hybrids: e.g. parallel voting+AMS (South Korea) | ||
Vote linkage | Positive vote transfer system (PVT)
| Supermixed:
|
mixed ballot transferable vote (MBTV) | ||
Seat linkage and vote linkage | Dual-member proportional (DMP) | Modified Bavarian MMP |
Non-compensatory mixed systems | ||
single vote systems | dual vote systems | |
No linkage | mixed single vote, unlinked versions (MSV)
| parallel voting |
Vote linkage (direct vote transfer) | mixed single vote, superposition
| - |
The first recorded mixed vote transfer systems (used in Germany) have been under the "losers plus surplus" model, [6] therefore, they inherently included "winner compensation". Under later definitions of certain sources, this model would also be retroactively a "negative vote transfer system" despite not using any votes with negative transfer value. The confusion stems from the terms "positive" and "negative vote transfer system" being coined based on the systems in use in the 1990s and early 2000s in Hungary and Italy and the inconsistent terminology of sources on these niche variants. While all the Hungarian versions primarily transferred votes with a positive value and the votes transferred were almost exclusively in compensation for losing candidates, the Italian models of scorporo operated only with a negative value and deducted all or a part of votes cast for local winners.
In one view, [4] positive vote transfer means vote transfer with only positive votes value, with or without winner compensation (which may be itself positive or negative). [12] This means that either only the positive transfer votes are used on the list tier to apportion seats (Hungarian local elections), or they are added to other (direct) list votes (Hungarian national elections). Negative vote transfer systems, meanwhile use the opposite principle, they subtract exactly those votes (from the direct list votes), which the equivalent positive vote transfer would not transfer. [4] In this way, these systems rely on negative value winner compensation, which is their most important property that determines how they can be manipulated.
Votes used to allocate list seats under | Positive vote transfer system | Negative vote transfer system | |
---|---|---|---|
Standalone | Supermixed | Supermixed | |
Without winner compensation | Only votes of losing candidates Used in: Hungarian local elections | Direct list votes + votes for losing candidates Used in: Hungarian national elections (formerly) | Direct list votes - votes for winning candidates excluding surplus votes Used in: Italian Senate (formerly) |
With winner compensation | Votes for losing candidates + surplus votes of winning candidates (e.g. votes of the winner above votes of the second placed candidate + 1) | Direct list votes + votes for losing candidates + surplus votes of winning candidates (e.g. votes of the winner above votes of the second placed candidate + 1) Used in: Hungarian national elections (currently) | Direct list votes - votes for winning candidates Used in: Italian Chamber of Deputies (formerly) |
In some sources, the Hungarian model of "losers only" has been labeled "positive vote transfer", [5] under this view the Italian Senate model, despite using only negative transfer votes would also be PVT, since it operates under the same "losers only" principle (deducting all of winners votes from the list vote). Conversely "negative vote transfer" means not only the Italian Chamber model of scorporo is (deducting the non-surplus votes of winners), but the original German variants and the current Hungarian electoral systems for national elections (it uses winner compensation with positive value). A third term of "direct vote transfer" has been used for vote transfer systems without compensation (mixed single vote equivalent of parallel voting). [11] This view has been criticized for using unintuitive terminology and not including models of winner compensation other than the surplus votes compared to the second place candidate[ citation needed ]. This article uses the former view to maintain consistency and to show the significance of positive/negative transfers on manipulation more intuitively.
Though the original vote linkage systems used the "losers plus surplus" model, the systems established in Hungary only used votes cast for losing candidates on the (relatively small sized) compensatory tier of the electoral systems. For this reason, when the system for the National Assembly was changed by the governing parties before the 2014 election, the introduction of transferring surplus votes (with a positive value) was a novel element in the system. This element was soon called "winner compensation" (mostly by its critics), who claimed it was effectively a majority bonus. [13] Together with other criticisms of the change (suspicions of gerrymandering, moving towards an even more mixed-majoritarian system, postal voting for non-resident citizens only etc.) this was viewed as a thinly veiled attempt to benefit the parties who created the system, without meaningful consultation of the opposition.
Some non-mixed systems, which use multi-member constituencies either on their single tier or also on their lower tier use vote linkage. An example is the national remnant system of Weimar Germany.[ citation needed ] This system used an absolute quota (not dependent on the vote shares in the district, rather a fixed number of votes) instead of plurality to elect candidates. With the fixed quota and a changing population, this meant a flexible parliament size.
The vote transfer to party list is the mixed single vote equivalent to indirect single transferable voting, while the direct equivalent to the single transfer vote is the mixed ballot transferable vote.
The features of vote linkage compensatory systems are similar to those of comparable parallel voting or mixed-member proportional systems, depending on which systems does the result more resemble. As mixed systems they usually inherit properties of their subsystems, in case of the most commonly used vote linkage systems, these are first preference plurality (in single-member districts) and closed list PR. Single vote variants also suffer from the disadvantages of the mixed single vote, however in certain systems this also gives robusticity against strategic manipulation.
Vote linkage systems generally give greater representation to smaller parties than parallel voting with the same amount of list seats, but usually not as much as comparable seat linkage systems - they usually cannot guarantee overall proportionality. Large parties can win very large majorities, disproportionate to their percentage vote, especially when vote linkage is employed in a supermixed system combined with parallel voting (such as in Hungary and Italy). In Hungary for example, in last 3 elections have resulted in a 2/3 supermajority of seats for the most popular list from at low as 45% of the vote in 2014.
Because some candidates are elected from constituencies and some from a list, there is a critique that two classes of representatives will emerge under any mixed system, including vote linkage ones: One class beholden to their electorate seat, and the other concerned only with their party. Some consider this as an advantage as local as well as national interests will be represented. Some prefer systems where every constituency and therefore every constituent has only one representative, while others prefer a system where every MP represents the electorate as a whole as this is reflected in the electoral system as well, while a vote linkage mixed system provides a compromise between these two views.
Vote linkage systems can be compared to the mixed-member proportional systems (MMP)/ additional member system (AMS) and the common form of mixed-member majoritarian representation, parallel voting.
Like in parallel voting, a party that can gerrymander local districts can win more than its share of seats. So parallel systems need fair criteria to draw district boundaries. (Under MMP a gerrymander can help a local candidate, but it cannot raise a major party's share of seats, while under AMS the effects of gerrymandering are reduced by the compensation)
Seat linkage and vote linkage systems both suffer from different potential manipulation strategies arising from their compensatory component, which the following table shows. [14] Parallel voting does not suffer from these by definition, since the worst case of strategic manipulation reverts compensatory systems to parallel voting.
Seat linkage | Vote linkage | No linkage | ||
---|---|---|---|---|
without winner compensation | with winner compensation | parallel voting | ||
Number of list seats needed for proportional results | Low | High | Very high | Extremely high (convergence, but never reaches) |
Proportional if there are more list seats than needed? | Yes (stays proportional) | No (flips to opposite directional disproportionality) | ||
Types of manipulation strategies (arising from mixed system, not subsystems) | Decoy lists (less vulnerability if MSV) | Stronghold-split (capturing surplus votes) Only if there are too many list seats: transfer-vote strategy If there is negative vote transfer: decoy lists | Only if there are too many list seats: transfer-vote strategy If there is negative vote transfer: decoy lists | None (no compensation mechanism to subvert) |
Vulnerability to strategic manipulation (subversion) of compensation if there are | N/A | |||
few compensatory seats | High | Low | None/very low | |
many compensatory seats | Medium | Medium | Low | |
very many compensatory seats | Medium | High | Medium | |
Relevance of increased strategic voting / nomination in winner-take-all tier if there are (with no subversion of compensation) | ||||
few compensatory seats | Medium to almost none | Medium | High | Very high |
many compensatory seats | Low to almost none | Low | Medium | High |
very many compensatory seats | Very low to almost none | Low | Low | Medium |
Country | Legislative body | In effect | Number of votes | System | Notes |
---|---|---|---|---|---|
West Germany (formerly) | Some state parliaments (formerly) [6]
| varied by state | One | Positive vote transfer with winner compensation | In Bremen and Hamburg, plurality was used in multi-member constituencies, though the latter switched to single-member constituencies in 1949. |
Hungary | National Assembly | 1990-2014 | Two | Supermixed positive vote transfer (3 tiers) no winner compensation from local SMDs with negative winner compensation from regional PR tier | Modified two round system in SMDs |
National Assembly [9] | 2014- | Two | Supermixed positive vote transfer with positive winner compensation from local SMDs | ||
Local elections municipalities and districts in the capital with a population over 10000 | 1990 | One | Positive vote transfer no winner compensation | Before 1994 with a two-round system | |
Budapest Assembly | 2014 and 2018 | One (DSV) | - | ||
Italy (formerly) | Chamber of Deputies | 1993-2005 | Two | Negative vote transfer partial negative winner compensation | |
Senate | One | Negative vote transfer full negative winner compensation |
The first recorded use of a vote-transfer based mixed system was in British occupied West Germany. German opposition to a purely winner-take-all system like first-past-the-post, that the British preferred, necessitated a compromise. The vote transfer system which was of the "losers plus surplus model" [6] included winner compensation and the majority of seats were won in single-member district would mostly keep the result as close to first-past-the-post as possible (see mixed-member majoritarian representation), while allowing for some compensatory representation of other parties ('The British called this a "modified PR system". The Germans more accurately (...) claimed that it was more like a modified majority system'). [15] Since then, all German states that used such a system have changed either to either the seats linkage-based (and significantly more proportional) MMP or a pure party-list proportional system. [6]
A re-emergence of the vote linkage mixed system started in the turn of the 1990s, when politicians in Hungary, in transition to a democracy, were deliberating what electoral system to adopt. In this transition many aspects of constitutional and governmental structure were adopted from Germany. For the National Assembly, one of the most complicated supermixed systems was developed as a compromise between a winner-take-all and a purely proportional system. This system used a modified two-round system in single-member districts, regional lists and a small number of national compensatory seats based on the votes cast for losers in the local districts. The system, however, had some small negative value winner compensation from the party-list PR of the regional multi-member districts as well. [5] Despite the sometimes highly disproportionate results, the system has often been mistaken for mixed-member proportional representation both inside and outside of Hungary, especially since it is common knowledge that it was derived from 'the' German system (hence the confusion with MMP). The losers only model because the predominant form of mixed system known and used in Hungary, with similar systems designed for local elections.
The system for the National Assembly was in use until the elections of 2014, since which a simplified, but much more distinctly mixed-member majoritarian system is used. [9]
National Assembly elections use a positive vote transfer system, [16] which also partially 'compensates' parties of winning candidates.
The compensatory tier of the National Assembly of Hungary is allocated to parties crossing a national 5% threshold. Votes of losing candidates as well as surplus votes of winning candidates are added to the list vote, making it a positive vote transfer system. Surplus votes are calculated by subtracting the result of the second-place candidate plus 1 from the result of the first place candidate, making the system similar to the Italian Chamber model of scorporo. However, because there are effectively no votes transferred with a negative value, the system is not subject to the same decoy list tactics as scorporo is. Instead, when decoy lists were mentioned in the context of the Hungarian system, it was in reference to the proliferation of unknown parties with similar names to known parties, fielding decoy lists (and decoy spoiler candidates) allegedly intended to confuse voters.[ citation needed ]
Local elections in municipalities and districts in the capital with a population over 10 000 use a mixed single vote with positive vote transfer, where only votes for losing candidates are transferred to the compensatory tier. [17] The vote transfer takes place based on the party affiliation of the local candidates and seats are allocated proportionally based on the transferred votes. [18]
For the 2014 and 2018 elections, General Assembly of Budapest was elected by a kind of mixed single vote, which served also as double simultaneous vote. The 23 directly elected mayors of the districts (plus the lord mayor) were ex officio members of the assembly alongside 9 members elected from compensation-lists of parties based on the votes cast for the mayoral candidates (Budapest mayor candidates and district mayor candidates could be listed on compensation-lists). The system was criticized for effectively using the vastly differently populated districts as electoral districts each election one member.[ citation needed ] For the 2024 election, the system was reverted to a direct election using party-list PR.
Because of the comparatively few compensatory seats, the system does not guarantee proportional results and commonly underrepresents smaller parties, however theoretically, it could also underrepresent larger parties compared to a list PR system.
A negative vote transfer system called scorporo was in force for elections to the bicameral Parliament of Italy based on Law 277/1993 from 1993 to 2005. Under this system, members could be elected in two ways:
The system was subject to the following specific rules for each chamber:
In the 2001 Italian general election, one of the two main coalitions (the House of Freedoms, which opposed the Scorporo system), linked many of their constituency candidates to a decoy list (lista civetta) for the proportional component, under the name Abolizione Scorporo (Abolish Scorporo). This list was not designed to win proportional seats, but only to soak up constituency votes for House of Freedoms, enabling them to win a larger share of the proportional list seats than they would be entitled to if all candidates were linked other House of Freedoms parties. This intentionally undermined the compensatory nature of the electoral system. As a defensive move, the other coalition, The Olive Tree, created their own decoy list under the name Paese Nuovo (New Country). This was facilitated by the fact that this particular scorporo system allowed the single-member constituency vote and the proportional list vote not to be linked. Decoy lists are a common issue in all compensatory and pseudo-compensatory systems, and this was not a unique problem for scorporo. Due to Silvio Berlusconi's opposition to the system, Italy changed to a majority bonus system in 2005.
Some properties of vote linkage, especially robusticity against certain types of tactical manipulation have lead to social choice theorists to develop variations and hybrid using vote linkage. Golosov argued for the use of vote linkage via mixed single vote, developing a system which requires less compensatory seats but adequate proportionality as compromise alternative to conventional MMP systems. [2] The mixed ballot transferable vote (MBTV) was proposed as a preferential variant of the mixed single vote where voters may indicate their preferences separately, and the original proposal also explores methods to make the system relatively proportional (as modifications to the systems used in Hungary). [12]
A system using a mixed single vote in dual member districts (with local lists up to two candidates) called dual-member proportional has been proposed for Canada by Sean Graham. [19] DMP uses both vote transfer (within districts) and seat linkage.
An open list variant of MMP (modified Bavarian MMP) has been proposed by Jameson Quinn [20] which uses a mixed ballot and vote linkage combined with classical seat linkage.
The vote linkage and seat linkage hybrid has been further refined by Markus Schulz, [21] where in the proposed system uses STV on the local tier, and the votes for the local winner are only counted as votes for that candidate's party to the proportion as it is necessary to eliminate overhang seats. The proposal also contains a flexible number of leveling seats to ensure full proportionality.
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. PR systems provide balanced representation to different factions, reflecting how votes are cast.
The additional-member system (AMS) is a two-vote seat-linkage-based mixed electoral system used in the United Kingdom 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 distinct from using parallel voting for the list seats in that the "additional member" seats are awarded to parties taking into account seats won in SMDs – these are ignored under parallel voting.
Mixed-member proportional representation is a type of representation provided by some mixed electoral systems which combine local winner-take-all elections with a compensatory tier with party lists, in a way that produces proportional representation overall. Like proportional representation, MMP is not a single system, but a principle and goal of several similar systems. Some systems designed to achieve proportionality are still called mixed-member proportional, even if they generally fall short of full proportionality. In this case, they provide semi-proportional representation.
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.
Electoral reform in New Zealand has been a political issue in the past as major changes have been made to both parliamentary and local government electoral systems.
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 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.
The Chamber of Deputies is the lower house of the Plurinational Legislative Assembly of Bolivia. The composition and powers of this house are established in the Political Constitution of the State. The session room is located in the Legislative Palace building in Plaza Murillo.
The majority bonus system (MBS), sometimes referred to as the reinforced proportionality electoral system is a semi-proportional method of electing multiple representatives. The majority bonus is typically classified as a mixed electoral system, as it integrates both the proportionality and winner-take-all principles to provide mixed-member majoritarian representation. An academic term for such a hybrid system is fusion, which means an independent combination of two systems in which the two formulas are mixed within the same district (the district in question may be a single, nationwide constituency). This makes it distinct from other mixed systems such as parallel voting (superposition) and coexistence. A majority bonus may also be one of the properties of a supermixed 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.
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 used to determine the results of an election. 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 bloc can win all seats in a legislature or electoral district, denying representation to any political minorities. Such systems are used in many major democracies. Such systems are sometimes called "majoritarian representation", though this term is a misnomer, as most such systems do not always elect majority preferred candidates and do not always produce winners who received majority of votes cast in the district, and they allow parties to take a majority of seats in the chamber with just a minority of the vote.
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 the additional member system in the UK in theory. However, the design proved particularly susceptible to the decoy list strategy, and as a result by 2001 had devolved into a de facto parallel voting system. The scorporo method is only known to have been used in Italy, but a similar version is in used for the National Assembly of Hungary.
The dual-member mixed proportional (DMP) voting method is a mixed electoral system using a localized list rule to elect two representatives in each district. It is similar to other forms of mixed-member proportional representation but differs in that all representatives are elected locally in small districts, rather than requiring separate list seats to be filled in large regional or nationwide districts. In the first step, one seat in each district is awarded to the candidate with the most votes, as with first-past-the-post voting rules. In the second step, underrepresented parties are assigned secondary seats in the districts in which they won the most votes, which creates an overall proportional result.
A mixed electoral system is one that uses different electoral systems to elect different seats in a legislature. Most often, this involves a winner-take-all component combined with a proportional component. 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. Systems that mix more than two components are sometimes called supermixed.
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.
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 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 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.
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.
Compensation or correction is an optional mechanism of electoral systems, which corrects the results of one part of the system based on some criterion to achieve a certain result, usually to make it more proportional. There are in general two forms of compensation: vote linkage and seat linkage.