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 are used in different regions of a country.
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The most prominent mixed electoral systems include mixed member proportional (MMP) and parallel voting, that latter of which 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 allocation
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.
Types of mixed systems
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 in many countries including Japan, South Korea, Taiwan, and Russia.
"單一選區兩票制（Single-District Two-Votes System）" for Chinese.
Mixed member proportional
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.
Alternative vote plus
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, 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. The system was used in Italy from 1993 to 2005, and is currently used in Hungary.
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 proportional
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.
List of countries using mixed systems
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.
- ACE Project Electoral Knowledge Network. "Electoral System Tiers and Hybrid Systems". Retrieved 20 October 2017.
- Bormann, Nils-Christian; Golder, Matt (2013). "Democratic Electoral Systems around the world, 1946–2011" (PDF). Electoral Studies. 32 (2): 360–369.
- 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.
- 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.
- 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.
- Marco Bertacche (March 2, 2018). "How Italy's New Electoral System Works". Bloomberg Politics.