|Part of the Politics series|
Parallel voting describes a mixed voting 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, some regions of Russia and elsewhere, sometimes known as the Supplementary Member system or, by some political scientists, Mixed Member Majoritarian (MMM), which combines first-past-the-post voting with party-list proportional representation. Parallel voting or MMM is distinct from mixed member proportional representation where there is one election, and the party vote determines what share of seats each party will receive in the legislature.
However, if the couple 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 councillors 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 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 amount, 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
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.
Advantages and disadvantages 
||This article contains a pro and con list. (November 2012)|
SM 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 PR.
A criticism of proportional voting 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 a 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, small parties may still be shut out of representation despite winning a substantial portion of the overall vote.
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 as a means by which incentives for greater party cohesiveness could be injected. 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 voting is only used within two established democracies worldwide; it is primarily used in Asian and Eastern European states.
- South Korea
- Palestinian Authority
- Vojvodina (Serbia)
Former use 
- Croatia (1993-2001)
- Italy (1993-2005)
- Republic of Macedonia (1998)
- Russia (1993-2003)
- Ukraine (1998-2005)
Azerbaijan's National Assembly (the Milli Məclis) had previously used a 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, 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 of the 2008 election was very low (1.32 on the Gallagher Index).
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 the plurality voting system that 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.
The commission came to the conclusion that SM would be unable to overcome the shortcomings of New Zealand’s previous plurality voting 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 voting 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, the clear majority (46.66%) preferred a return to the pre-1994 plurality voting system (also known as first-past-the-post, FPTP). Supplementary member was the second most populous choice, with 24.14% of the vote.
See also 
- A Handbook of Electoral System Design from International IDEA
- Electoral Design Reference Materials from the ACE Project
- Accurate Democracy suggests Parallel Voting by PR and Condorcet rules to make a balanced council with a few central swing voters.
- 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.
- Reynolds et al (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electcoral Assistance, pg. 104
- Reynolds et al (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electcoral Assistance, pg. 112
- The Standard (2009) http://www.thestandard.org.nz/the-emerging-consensus-to-keep-mmp/ accessed: 8, May, 2010
- Reynolds et al. (2008), Electoral System Design: The New International IDEA Handbook, Sweden: International Institute for Democracy and Electoral Assistance, pg. 30–33
- Election Rigging and How to Fight It Journal of Democracy - Volume 17, Number 3, July 2006, pp. 138-151.
- 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.