User:Mathew Grange/Sandbox

Supplementary Member (SM) is a mixed voting system that uses parallel voting. SM combines plurality voting (often called "first past the post" (FPP)) with proportional representation (PR).

Supplementary Member is a form of proportional representation in which a party is awarded supplementary seats in parliament (or the legislature) alongside the seats won through constituencies (see alsoelectoral district). The amount of supplementary seats awarded to a party is determined by the amount of votes received in the constituencies. Any supplementary seats won by a party are filled from an ordered list of nominated candidates (see list MP) ^[1] —if a party is awarded ten supplementary seats, these would be filled by the top ten candidates on their list. The number of supplementary seats availabe would determine the threshold of votes a party must secure before being ensured a list seat. For instance, if there were a pool of 20 supplementary seats allocated by the modified Sainte-Laguë method, then a party would need to get approximately 5% of overall constituency votes for a first seat and 6.8% for a second ^[2] .

The balance between plurality/majority constituency seats and list seats can vary widely, ranging from 81% of South Korea's seats being elected by constituency to only 14.8% in Timor-Leste. In most cases the balance is more even, as is the case in Japan where 60% of seats are determined by constituencies ^[3] .

An advantage of SM (and of parallel systems in general) is that minority parties who would be unsuccessful under a plurality/majority system would win some seats through proportional allocation. It is also argued that SM does not lead to the degree of fragmentation found in party systems under pure forms of PR ^[4] .

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 (as can also happen under MMP): 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 ^[5] . Because the percentage of list seats allocated is tied to the number of electorate seats won, SM has been characterised by some political commentators as a system that awards a 'winners bonus' ^[6] .

Parallel voting is only used within 2 established democracies worldwide, it is primarily used in Asian and Eastern European states ^[7] . Amongst the countries using SM, or some other form of Parallel voting are: Andora, Armenia, Georgia, Guinea, Japan, Kazakhstan, South Korea, Lithuania, Monaco, Pakistan, Phillipines, Russia, Senegal, Seychelles, Taiwan, Tajikstan, Thailand, Timor-Leste, Tunisia and the Ukraine ^[8] .

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 ^[9] , the limited proportionality that SM was able to offer had little effect.

Georgia's Parliament has 150 members, known as deputies, from which 75 members are proportional representatives and 75 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 elction 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.

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 ^[10] .

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) ^[11] . New Zealand adopted a MMP electoral system, as recommended by the Royal Commission, in the 1993 electoral referendum.

It is possible that SM may be considered again as a possible electoral system within New Zealand—despite the country currently having one of the most proportional electoral systems in the world under MMP (see Gallagher Index).