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The most common type of MMM system is the supplementary member (SM) system (a form of parallel voting), whereby representatives are voted into a chamber using at least two different systems independently of each other. Most commonly this combines first-past-the-post (single member plurality) voting (FPTP/SMP) with party-list proportional representation (list-PR). The system has been applied in the election of national parliaments as well as local governments in various places such as Taiwan, Lithuania, Russia and Kazakhstan. While FPTP with list-PR is the most common pairing in parallel systems, any other combination is effectively possible. Therefore, not all parallel voting systems are mixed-member majoritarian (and not all MMM systems are strictly parallel - non-compensatory), however as most of them used in practice are, the terms are sometimes used interchangeably.
According to the academic typology of Massicotte & Blais (1999), mixed-member majoritarian systems can come in the following forms:
Superposition, or the supplementary member (SM) system where two different systems are used on different levels of the electoral system in a non-compensatory manner. This means if a party gets a disproportionally high share of seats in the majoritarian tier, they retain this absolute advantage even as their relative (percentage-wise) advantage may decrease due to a proportional component.
Parallel voting is defined by the voter having two votes and there being no interaction between the two (or more) component systems of the election, most often a first-past-the-post vote and a list-PR vote. There are also examples for two-round system and list-PR (Lithuania) or party block voting and list-PR (Andorra).
There also exists a single vote version of superposition systems, in which the voter may not split their votes on the different levels of the election, but a single vote automatically determines both the local candidate and the party choice of the voter. Such a system is used in Italy(Rosatellum) for both houses of parliament which disallows vote splitting, thereby effectively using a mixed single vote.
In some systems, such as the one used in Pakistan, list PR seats are not distributed based on votes cast, but proportionally with seats already won by the parties using FPTP/SMP. This means the winning parties absolute advantage over other parties increases in terms of seats won, and their relative (percentage-wise) majoritarian advantage stays the same.
Fusion, or majority jackpot or majority bonus system (MBS) used in Italy and France for regional elections or where a group of councilors are chosen with a general ticket, and the remaining part by a party-list proportional system, so to ensure that a single list wins well over half the seats.
Correction or compensation: Although compensation is the basis of mixed proportional (MMP) systems, some countries use systems which have so limited (compensatory) interaction between the local (FPTP/SMP) and national (list-PR) tiers, that in practice it qualifies more as MMM. Certain implementation of the additional-member system can be considered MMM or MMP or inbetween: proportionality varies based on the results of specific elections. This is especially the case, when a compensatory system is subverted by manipulation intended to negate the correction, which has been the case in multiple countries using MMP./AMS.
A diagram of a coexistence based mixed electoral system combining first-past-the-post and party-list proportional representation.Coexistence: some type of mixed systems do not have two tiers (and so also use a single vote), but use majoritarian representation in many constituencies (single-member districts) but use proportional representations is some (multi-member districts), which makes the system as a whole mixed-member majoritarian if the winner-take-all districts are not just rare exceptions.
Supermixed: In Hungary, elections to the National Assembly use the list vote as a parallel system would, but also add unused votes ("fractional votes" of both district winners and losers). In South Korea most list seats are allocated non-compensatory (supplementary members) as in parallel voting, but a small part of list seats (additional members) is allocated using the additional member system (AMS), which makes it partially compensatory (the effect however is cancelled by the party-list splitting strategy).
Advantages and disadvantages
General
Mixed-member majoritarian systems generally allow smaller parties that cannot win individual elections to secure some representation in the legislature; however, unlike in a proportional system, they will have a substantially smaller delegation than their share of the total vote. It is also argued that MMM does not lead to the degree of fragmentation found in party systems under forms of proportional representation, which some consider to be an advantage and some a disadvantage.
A criticism of adding a proportional component to winner-take-all electoral systems is that the largest parties are more likely to rely on the support of smaller ones in order to form a government, than if the system was majoritarian only. However, smaller parties are still disadvantaged as the larger parties still predominate. In countries where there is one dominant party and a divided opposition, the proportional seats may be essential for allowing an effective opposition. Furthermore, the likelihood of no governing majority is dependent on many other factors, same as under first-past-the-post. In many democracies, coalition governments are not only the norm, but seen as desirable as the government is formed with wider (indirect) support of the electorate and via compromise between factions.
In parallel voting and other supplementary member systems, it is sometimes considered a negative, that there are two classes of representatives with one class beholden to their electorate seat, and the other concerned only with their party.
The major critique of MMM systems is that they cannot guarantee overall proportionality. Large parties can win very large majorities, disproportionate to their percentage vote. For example, in the 2014 Hungarian election, the Fidesz/KDNP grouping won 133 of 199 Parliamentary seats with 44.87% of the overall vote.
Combined with a high threshold, small parties may still be shut out of representation entirely despite winning a substantial portion of the overall vote. So that their constituency vote is not wasted, voters may vote for a large party's local candidate tactically, while voters of large parties may vote for allied smaller parties with their list vote so as to help them over the threshold. An example of this being played out can be seen in the 2014 Japanese election where the government's junior coalition partner, Komeito took only 1.5% in the local constituencies, but 13.7% on the PR list. Most of the Komeito votes came from the ruling Liberal Democratic Party.
Compared to mixed member proportional
Mixed-member majoritarian (MMM) systems are often contrasted with mixed-Member proportional (MMP) systems. There are a unique set of advantages and disadvantages that apply to this specific comparison.
Under MMM 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. Normally, under mixed member proportional representation a gerrymander can help a local candidate, but it cannot raise a major party's share of seats, unless the compensatory link is effectively disentangled, for example using decoy lists and tactical voting.
In Japan, an electoral system based on a single-seat constituency system was introduced in 1994 to facilitate a change of government and prevent corruption. It was decided that a portion of the seats would be elected through a proportional representation system to accommodate minority parties. In Japan's political culture, however, this system further reinforced the dominant-party system, and except for a brief period between 2009 and 2012, the opposition parties faced the LDP as a minority force, aided by the proportional representation system. And subsequently Thailand and Russia adopted a parallel system to provide incentives for greater party cohesiveness.
The party is sure to elect the candidates at the top of its list, guaranteeing safe seats for the leadership. By contrast, under the MMP system a party that does well in the local seats might not need or receive any compensatory list seats, so the leadership has to run in the local seats. On the other hand, because of the low reputation of lawmakers elected by proportional representation in Japan, party leaders of major parties are implicitly expected to be elected in their electoral districts. Although political parties can designate the order of the list, it is customary for the order to change according to the percentage of close defeats.
Mixed-member majoritarian systems support the creation of single-party majorities more often than mixed proportional member systems. This may be a positive or a negative depending on the view of the voter.
Use
Current use
Lower (or only) house of legislature chambers
Upper house of legislature chambers (where applicable)
Countries using mixed-member majoritarian electoral systems.
Other
First past the post (FPTP/SMP) + PR seats in proportion to FPTP seats Mixed Party block voting / General ticket (PBV) + FPTP/SMP or FPTP/SMP + majority jackpot (supermixed) Mixed-member majoritarian / parallel voting (FPTP/SMP + party-list PR) Mixed-member majoritarian / parallel voting (TRS + party-list PR) Mixed-member majoritarian / parallel voting (BV or PBV + party-list PR) Mixed-member majoritarian with compensation / scorporo (FPTP/SMP + party-list PR) Majority bonus system (MBS) / Majority jackpot system (PBV + party-list PR)
Varies by federal states or constituencies No direct election No information
Mixed-member majoritarian systems are primarily used in Asian and some of the European states.
party with over 50% of vote gets all seats in multi-member constituencies (party block voting), otherwise highest party gets half, rest distributed by largest remainder (Hare quota)
First-past-the-post (FPTP/SMP) party with over 50% of vote gets all seats in multi-member constituencies (party block voting), otherwise List PR (largest remainder, closed list)
80% of seats (rounded to the nearest integer) in each constituency are awarded to the party receiving the most votes (party block voting), remaining seats are allocated proportionally to other parties receiving over 10% (closed list, D'Hondt method)
Georgia's Parliament has 150 members, known as deputies, from which 120 members are proportional representatives and 30 are elected through a single-member district plurality system to represent their constituencies. Five parties and electoral blocs had representatives elected to the parliament in the 2008 elections: the United National Movement (governing party), The Joint Opposition, the Christian-Democrats, the Labour Party and Republican Party. Due to the large amount of support given to the ruling party the disproportionality of the 2008 election was very low (1.32 on the Gallagher Index).
local electoral districts within country/capital borders and a single nationwide constituency that includes non-resident with Hungarian citizenship as well
Hungary's National Assembly uses a system where the parallel voting component shares a pool of seats (93) with the compensatory vote transfer system and with the minority list seats with a reduced entry threshold. This means, the number of seats effectively assigned proportionally based on the parallel party list votes is unknown/unknowable before the election takes place.
Before the 2014, a different mixed system was used with a two-round system in single-member districts.
Starting with the 2018 election, both houses of the Italian parliament are elected using a system similar to parallel voting. 62.5% of the seats are assigned proportionally to party lists; party lists are also linked in coalitions supporting constituency candidates running for the remaining 37.5% of the available seats, who are elected by means of a first-past-the-post system. Electors have a single vote with two-fold proportional effects for a party list and its associated coalition candidate (split-ticket voting is not allowed).
South Korea's National Assembly used parallel voting from 1988 to 2019. Since 2019, it uses a hybrid system of parallel voting and mixed-member proportional, with both compensatory seats (30) and supplementary seats (17).
The Kazakhstan Parliament has two chambers: the Assembly and the Senate. The Assembly (Mäjilis) has 98 seats, 29 of these are constituency seats and 69 list seats determined by proportional representation.
Two-round system (TRS) in single-member districts, two-round block voting (BV) in dual-member districts, and List PR (simple quota largest remainder; closed-list) in larger districts + twice 20 nationally List PR (one set of 20 reserved for women)
Since 1996, a party cannot get more seats overall than 8% above its result nationally (i.e., to win 50% of the legislative seats, a party must win at least 42% of the vote nationwide). There are three exceptions on this rule: first, a party can only lose PR-seats due to this rule (and no plurality-seats); second, a party can never get more than 300 seats overall (even if it has more than 52% of the vote nationally); and third, a party can exceed this 8% rule if it wins the seats in the single-member districts.
Superposition using a single party vote: Limited (party) block voting locally (2 seats from each constituency to largest party, 1 to the second largest party) + Party-list PR nationwide
128
three-seat constituencies corresponding to the nation's 31 states and Mexico City (the former Federal District which is the national capital) and a nationwide electoral district
First-past-the-post (FPTP/SMP) in single-member districts, Saripolo or Sartori method (Largest remainder, but remainders only for those with no seats) in multi-member districts
The Philippines' electoral system for Congress is an exceptional case on this list. Political parties running for party-list seats are legally required to be completely separate from those running in constituency seats. Furthermore, political parties are capped at 3 seats (out of 61). As a result, the mixed-member system utilized in the Philippines is not representative at all of the share of the vote that "normal" political parties obtain (even amongst mixed-member majoritarian systems), let alone for those in full proportional representation systems.
single- or multi-member constituencies based on the 35 departments, with an additional 15 elected by overseas voters and a single nationwide constituency
1 (local districts), up to 10 (nationwide constituency)
First-past-the-post (FPTP/SMP) for 26 seats + up to a further ten are elected based on the percentage of votes received by each party; for each 10% of the total national vote received, a party gets one additional sea (List PR)
35 (currently, may vary based on election results)
single member constituencies and a single nationwide constituency
Azerbaijan's National Assembly used an SM system in which 100 members were elected for five-year terms in single-seat constituencies and 25 were members were elected by proportional representation. Since 2020 it uses FPTP.
In New Zealand, the Royal Commission on the Electoral System reviewed the electoral system in 1985–86 and considered SM to be a possible replacement for plurality voting, which was in use at the time. They suggested the supplementary member system could be implemented in New Zealand with the following features: each elector would have 2 votes, 1 for a constituency candidate and the other for a party list; there would be a total of 120 seats, with 90 seats determined by votes in constituencies and the remaining 30 from party lists; a modified Sainte-Laguë method would be used to allocate list seats proportionate to a party's total share of votes, a threshold of 5% was suggested before parties could be allocated seats.
The commission came to the conclusion that SM would be unable to overcome the shortcomings of New Zealand's previous plurality electoral system (FPP). The total seats won by a party would likely remain out of proportion to its share of votes—there would be a “considerable imbalance between share of the votes and share of the total seats”—and would be unfair to minor parties (who struggle to win constituency seats). In the indicative 1992 electoral referendum, SM was one of the four choices of alternative electoral system (alongside MMP, AV and STV), but came last with only 5.5 percent of the vote. By clear majority, a change to MMP was favoured, as recommended by the Royal Commission, and was subsequently adopted after the 1993 electoral referendum.
In another referendum in 2011, 57.77% of voters elected to keep current the MMP system. Among the 42.23% that voted to change to another system, a plurality (46.66%) preferred a return to the pre-1994 plurality electoral system (also known as First-past-the-post, FPTP). Supplementary member was the second-most popular choice, with 24.14% of the vote.
^ Massicotte & Blais (1999). "Mixed electoral systems: a conceptual and empirical survey". {{cite journal}}: Cite journal requires |journal= (help)
Reynolds et al (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electoral Assistance, pg. 112
Reynolds et al. (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electoral Assistance, pg. 30–33
Gallagher 2011, p. 185 sfnm error: no target: CITEREFGallagher2011 (help); Gallagher 2014, p. 18 sfnm error: no target: CITEREFGallagher2014 (help).
Lublin, David. "Albania". Election Passport. American University. Retrieved 24 March 2016.
^ Royal Commission on Electoral Systems (1986), Report of the Royal Commission on the Electoral System: towards a better democracy, Wellington N.Z.: Government Printing, pg. 39.
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