Parallel voting

Mixed-member proportional representation Argentina South Korea

Parallel voting describes a mixed electoral system where voters in effect participate in two separate elections for a single chamber using different systems, and where the results in one election have little or no impact on the results of the other.

Specifically, it usually refers to the semi-proportional system used in Japan, South Korea, Taiwan, Russia and elsewhere, sometimes known as the supplementary member (SM) system or, by some political scientists, mixed member majoritarian (MMM), which combines first-past-the-post voting (FPTP) with party-list proportional representation (PR). Parallel voting or MMM is distinct from mixed-member proportional representation (MMP) where a single election takes place, and the party vote determines what share of seats each party will receive in the legislature to "top up" its constituency seats.

Whilst FPTP-PR is the most common pairing in parallel systems, any other combination is effectively possible. For example, in Italy and France, regional elections are held under a parallel system where a group of councilors are chosen by a party-list system, and the remaining part with a general ticket, so to ensure that a single list wins well over half the seats.


Under a supplementary member system (SM), which is a form of semi-proportional representation, a portion of seats in the legislature are filled by pluralities in single-member constituencies. The remainder are filled from party lists, with parties often needing to have polled a certain quota, typically a small percentage, in order to achieve representation, as is common in many proportional systems. Any supplementary seats won by a party are filled from an ordered list of nominated candidates[1]

Unlike mixed-member proportional, where party lists are used to achieve an overall proportional result in the legislature, under SM, proportionality is confined only to the list seats. Therefore, a party that secured, say, 5% of the vote will have only 5% of the list seats, and not 5% of all the seats in the legislature.

The proportion of list seats compared to total seats ranges widely; for example, 18.7% in South Korea, 30% in Taiwan, 37.5% in Japan and 68.7% in Armenia.[2]

Advantages and disadvantages


The supplementary member system allows 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 SM does not lead to the degree of fragmentation found in party systems under pure forms of proportional representation.[3]

A criticism of proportional electoral systems is that the largest parties need to rely on the support of smaller ones in order to form a government. 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.

Because the vote is split between constituencies and a list, there is a chance that two classes of representatives will emerge under an SM system: with one class beholden to their electorate seat, and the other concerned only with their party.

The major critique of parallel 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. Small parties may still be shut out of representation despite winning a substantial portion of the overall vote.[4] An example of this being played out in reverse 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

Parallel systems are often contrasted with Mixed Member systems. There are a unique set of advantages and disadvantages that apply to this specific comparison.

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 mixed member proportional representation a gerrymander can help a local candidate, but it cannot raise a major party’s share of seats.)

Countries like Japan, Russia, and Thailand 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 will not need or receive any compensatory list seats, so the leadership has to run in the local seats.

Parallel systems support the creation of single-party majorities more often than mixed member systems, this may be a positive or a negative depending on the view of the voter.


Current use

Parallel voting is primarily used in Asian and some of the European states.[5]

Country Seats constituency % Seats proportional representation % Seats other %
Andorra 14 50% 14 50%
Córdoba Province (Argentina) 26 37% 44 63%
Georgia 73 49% 77 51%
Guinea 39 34% 76 66%
Hungary 106 53% 93 47%
Italy 232 37% 398 (386 in Italy + 12 abroad) 63%
Japan 289 62% 176 38%
Republic of Korea 253 84% 47 16%
Lithuania 71 50% 70 50%
Mexico 300 60% 200 40%
Nepal 165 60% 110 40%
Palestine[6] 132 50% 132 50%
Russia 225 50% 225[7][8] 50%
Senegal 105 64% 60 36%
Seychelles 25 76% 8 24%
Pakistan 272 80% 70 (60 for women + 10 minorities) 20%
Philippines 245 80% 61 20%
Río Negro Province (Argentina) 22 48% 24 52%
San Juan Province (Argentina) 19 53% 17 47%
Santa Cruz Province (Argentina) 14 58% 10 42%
Republic of China (Taiwan) 73 65% 34 30% 6 for indigenous citizens 5%
Tanzania[9] 264 67% 113 (women-only lists) 29% 5 indirectly elected + 1 attorney general + 10 nominated by President 4%
Ukraine 225 50% 225 50%
Venezuela[10] 113 68% 51 31% 3 for indigenous 2%
Vojvodina (Serbia)[citation needed]

Former use


Azerbaijan's National Assembly (the Milli Məclis) had previously 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 the latest election Azerbaijan has returned to electing members from single-member constituencies. Due to the corruption present within Azerbaijan,[15] the limited proportionality that SM was able to offer had little effect.


Georgia's Parliament has 150 members, known as deputies, from which 77 members are proportional representatives and 73 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).


Starting with the 2018 election, both houses of the Italian parliament are elected using a form of 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).


The Kazakhstan Parliament has two chambers: the Assembly and the Senate. The Assembly (Mazhilis) has 77 seats, 67 of these are constituency seats and 10 list seats determined by proportional representation.

Proposal for New Zealand

The Royal Commission on the Electoral System reviewed the New Zealand 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 SM 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.[16]

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).[16] 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.


  1. ^ 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. 33.
  2. ^ Reynolds et al (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electoral Assistance, pg. 104
  3. ^ Reynolds et al (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electoral Assistance, pg. 112
  4. ^ The Standard (2009) http://www.thestandard.org.nz/the-emerging-consensus-to-keep-mmp/ accessed: 8, May, 2010
  5. ^ Reynolds et al. (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electoral Assistance, pg. 30–33
  6. ^ Also uses the additional voting system.
  7. ^ "Putin Orders New System for Russian Parliamentary Elections - NYTimes.com". 2013-01-03. Retrieved 2014-09-09.
  8. ^ Since the 2016 election, and from 1993 to the 2003 election.
  9. ^ "Art. 66, Constitution of Tanzania". Constitute Project.
  10. ^ "113 diputados serán electos por voto nominal y 51 por voto lista en parlamentarias". Agencia Venezolana de Noticias. 7 May 2015. Archived from the original on 22 October 2015. Retrieved 29 March 2019.
  11. ^ Gallagher 2011, p. 185; Gallagher 2014, p. 18.
  12. ^ Lublin, David. "Albania". Election Passport. American University. Retrieved 24 March 2016.
  13. ^ Bangkok Pundit (10 February 2016). "The effects of Thailand's proposed electoral system". Asian Correspondent. Retrieved 29 March 2019.
  14. ^ Kendall, Dave (6 January 2019). "Explainer: New rules for the House of Representatives". Bangkok Post. Retrieved 29 March 2019.
  15. ^ Election Rigging and How to Fight It Journal of Democracy - Volume 17, Number 3, July 2006, pp. 138-151.
  16. ^ a b 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.