Mixed electoral system
A mixed electoral system is an electoral system that combines a plurality/majoritarian voting system with an element of proportional representation (PR). The plurality/majoritarian component is usually first-past-the-post voting (FPTP), whereas the proportional component is most often based on party list PR. A distinguishing characteristic of mixed systems is the fact that every voter can influence both the plurality/majoritarian and PR aspects of an election. In a hybrid system, by contrast, different electoral formulas simultaneously, these may manifest in coexistence, when are different methods are used used in different regions of a country or when a parallel system is combined with a vote transfer system (e.g. scorporo).
The most prominent mixed electoral systems include mixed-member proportional representation (MMP) and parallel voting, of which the latter is also known as mixed member majoritarian (MMM). MMP generally produces proportional election outcomes, meaning that a political party which wins n% of the vote will receive roughy n% of the seats. Parallel voting tends to produce semi-proportional outcomes: more proportional than a plurality/majoritarian system but less proportional than a PR electoral system. Both parallel voting and MMP feature two tiers of elected representatives: one associated with the plurality/majoritarian component and one associated with PR. It is not necessary, however, for a mixed system to have multiple electoral tiers.
Compensatory/non-compensatory seat allocationEdit
A distinction is often made between mixed compensatory systems and mixed non-compensatory systems. In both types of systems, one set of seats is allocated using a plurality/majoritarian method. The remaining seats are allocated to political parties using a proportional allocation method such as highest averages or largest remainder. In mixed non-compensatory systems, which are also known as a parallel systems, the proportional allocation is performed independently of the plurality/majoritarian component. In mixed compensatory systems, the allocation of PR seats is adjusted to compensate for disproportionality caused by the plurality/majoritarian component.
The following hypothetical example by Massicotte illustrates how PR seats are typically allocated with compensation and without. The example assumes a 200-seat legislative assembly where 100 seats are filled using FPTP and the other 100 seats are awarded to parties using a form of PR. The table below gives the popular vote and FPTP results. The number of PR seats allocated to each party depends on whether compensation is used.
|Party||Popular vote||FPTP seats||PR seats||Total seats (FPTP + PR)|
Without compensation, each party wins its proportional share of the 100 PR seats. However, as shown below, the total number of seats (FPTP + PR) is not proportional to the popular vote. Party A only slightly outperformed Party B according to the popular vote, but receives significantly more seats due to its success in the FPTP contests.
|Party||Popular vote||FPTP seats||PR seats (non-compensatory)||Total seats (FPTP + PR)|
|Party A||44%||65||44||109 (54% of assembly)|
|Party B||40%||34||40||74 (37% of assembly)|
|Party C||10%||1||10||11 (6% of assembly)|
|Party D||6%||0||6||6 (3% of assembly)|
However, if the PR seats are allocated in a fully compensatory manner, then the total number of seats awarded to each party is proportional to the popular vote. As shown below, Party B wins 34% of the FPTP seats, is awarded 46% of the PR seats, and ends up with 40% of the seats in the assembly (the same as its share of the popular vote).
|Party||Popular vote||FPTP seats||PR seats (compensatory)||Total seats (FPTP + PR)|
|Party A||44%||65||23||88 (44% of assembly)|
|Party B||40%||34||46||80 (40% of assembly)|
|Party C||10%||1||19||20 (10% of assembly)|
|Party D||6%||0||12||12 (6% of assembly)|
In practice, compensatory seat allocation is complicated by the possibility that one or more parties wins so many seats under the plurality/majoritarian component that the designated number of PR seats is insufficient to produce a fully proportional outcome. Some mixed compensatory systems have rules that address these situations by adding extra PR seats until the next election.
The two common ways compensation occurs are seat linkage compensation (or top-up) and vote linkage compensation (or vote transfer). Compensation can occur either based on the same set of votes (voters vote for a local candidate and the party that candidate belongs to as the same time) or a second set of list votes.
|(mixed) single vote||(mixed) dual vote|
|Seat linkage||MSV (top-up)||MMP|
|Vote linkage||MSV (positive vote transfer)||Scorporo/negative vote transfer (hybrid: MSV combined with parallel voting)|
Types of mixed systemsEdit
Parallel voting is a mixed non-compensatory system with two tiers of representatives: a tier of single-member district representatives elected by a plurality/majoritarian method such as FPTP, and a tier of regional or at-large representatives elected by a separate proportional method such as party list PR. It is used for the first chamber (lower house) in many countries including Japan, South Korea, Taiwan, and Russia.
"並立制（Mixed member Majority）" for Chinese.
Mixed member proportionalEdit
Similar to parallel voting, MMP has a tier of district representatives typically elected by FPTP, and a tier of regional or at-large representatives elected by PR. Unlike parallel voting, MMP is a mixed compensatory system, meaning that the PR seats are allocated in a manner that corrects disproportionality caused by the district tier. MMP is used by Germany, Bolivia, Lesotho, and New Zealand. The additional member system refers to MMP models used in parts of the UK (Scotland and Wales), where small regions with a fixed number of seats tend to produce only moderately proportional election outcomes.
"聯立制（Mixed member Proportional）" for Chinese
Alternative vote plusEdit
AV+ is a mixed compensatory system similar to the additional member system, with the notable difference that the district seats are awarded using the alternative vote. The system was proposed by the Jenkins Commission as a possible alternative to FPTP for elections to the Parliament of the United Kingdom.
Scorporo is a two-tier mixed system similar to MMP in that voters have two votes (one for a local candidate on the lower tier, and one for a party list on the upper tier), except that disproportionality caused by the single-member district tier is partially addressed through a vote transfer mechanism. Votes that are crucial to the election of district-winning candidates are excluded from the PR seat allocation, for this reason the method used by scorporo is referred to as a negative vote transfer system. The system was used in Italy from 1993 to 2005, and a modified version is currently used in Hungary. Unlike scorporo, this version uses a positive vote transfer system, in which "wasted" votes (including surplus votes of winners) are added to the results of the party list vote, in this respect it is a hybrid of parallel voting and the mixed single vote.
Electoral systems with a majority bonus have been referred to as "unconventional mixed systems". Employed by Armenia, Greece, and San Marino, as well as Italy from 2006 to 2013, majority bonuses help the most popular party or alliance win a majority of the seats with a minority of the votes, similar in principle to plurality/majoritarian systems. However, PR is used to distribute seats among the opposition parties, and possibly within the governing alliance.
Dual member proportionalEdit
DMP is a mixed compensatory system similar to MMP, except that the plurality and PR seats are paired and dedicated to dual-member (two seat) districts. Proposed as an alternative to FPTP for Canadian elections, DMP appeared as an option on a 2016 plebiscite in Prince Edward Island and a 2018 referendum in British Columbia.
Mixed single voteEdit
MSV is a mixed compensatory type of systems using only a single vote that serves both as a vote for a local candidate and as a transfer vote on the compensatory tier. Similar to MMP, proportionality depends on the exact parameters to such a system, but it differs in that vote linkage (vote transfer) is used instead of seat linkage and split ticket voting is not possible. The system was used in Germany, and is currently used in Hungary for some local elections and in a modified form also for national elections (combined with parallel voting as part of a more complex system).
Mixed ballot transferable voteEdit
MBTV is a mixed compensatory type of systems similar to MSV, except voters can vote separately for a local candidate and as a transfer vote on the compensatory tier. It is different from MMP/AMS and AV+ in that there vote linkage instead of seat linkage used between tiers, so the two parts of the dual ballot are tied, so that only the list votes of ballots that would be used as transfer votes in an equivalent MSV counted. A similar dual vote, vote transfer based system is currently used in Hungary for national legislative elections.
List of countries using mixed systemsEdit
The table below lists the countries that use a mixed electoral system for the first chamber of the legislature. Countries with hybrid (or coexistence) systems have been excluded from the table, as have countries that mix two plurality/majoritarian systems. (See also the complete list of electoral systems by country.)
- "Electoral System Design: The New International IDEA Handbook". International Institute for Democracy and Electoral Assistance. 2005.
- ACE Project Electoral Knowledge Network. "Mixed Systems". Retrieved 20 October 2017.
- Norris, Pippa (1997). "Choosing Electoral Systems: Proportional, Majoritarian and Mixed Systems" (PDF). Harvard University.
- Massicotte, Louis (2004). In Search of Compensatory Mixed Electoral System for Québec (PDF) (Report).
- "Electoral Systems and the Delimitation of Constituencies". International Foundation for Electoral Systems. 2 Jul 2009.
- Bochsler, Daniel (May 13, 2010). "Chapter 5, How Party Systems Develop in Mixed Electoral Systems". Territory and Electoral Rules in Post-Communist Democracies. Palgrave Macmillan. ISBN 9780230281424.
- Bormann, Nils-Christian; Golder, Matt (2013). "Democratic Electoral Systems around the world, 1946–2011" (PDF). Electoral Studies. 32 (2): 360–369. doi:10.1016/j.electstud.2013.01.005.
- Bochsler, Daniel (2012). "A quasi-proportional electoral system 'only for honest men'? The hidden potential for manipulating mixed compensatory electoral systems" (PDF). International Political Science Review. 33 (4): 401–420. doi:10.1177/0192512111420770. S2CID 154545923.
- Golosov, G. V. (2013). "The Case for Mixed Single Vote Electoral Systems". The Journal of Social, Political, and Economic Studies.
- Bochsler, Daniel; Golder, Matt (2014). "Which mixed-member proportional electoral formula fits you best? Assessing the proportionality principle of positive vote transfer systems" (PDF). Representation. 50 (1): 113–127. doi:10.1080/00344893.2014.902222. S2CID 153691414.
- Ferrara, F (2003). "Electoral coordination and the strategic desertion of strong parties in compensatory mixed systems with negative vote transfers". Electoral Studies.
- Le Breton, Michel; Lepelley, Dominique; Merlin, Vincent (2015). "The probability of casting a decisive vote in a mixed-member electoral system using plurality at large" (PDF).
- Bedock, Camille; Sauger, Nicolas (2014). "Electoral Systems with a Majority Bonus as Unconventional Mixed Systems". Representation. 50 (1): 99–12. doi:10.1080/00344893.2014.902220. S2CID 154685383.
- Marco Bertacche (March 2, 2018). "How Italy's New Electoral System Works". Bloomberg Politics.
- "Electoral incentives and the equal value of ballots in vote transfer systems with positive winner compensation".
- Political Capital (2012). "The New Electoral Law in Hungary — In-depth Analysis" (PDF).