﻿ Additional Member System : définition de Additional Member System et synonymes de Additional Member System (anglais)

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Additional Member System


The Additional Member System (AMS) is the term used in the United Kingdom for the mixed member proportional representation voting system used in Scotland, Wales and the London Assembly.

Also, AMS as a generic term could refer to either the mixed member proportional representation system or the parallel voting system, a semi-proportional voting system. In both cases, some representatives are elected from single-winner geographic constituencies and others are elected under proportional representation from a wider area, usually by party lists. Voters usually have two votes, one for the party and the second for the candidate in a constituency, even if sometimes these votes are combined. The constituency representatives are generally elected under the first-past-the-post voting system. The party representatives are elected by a party vote, where the electors vote for a political party, and usually not directly for an individual. The particular individuals selected come from lists drawn up by the political parties before the election, at a national or regional level. Basic technical and political differences intervene between these two systems.

  • Under the mixed member proportional representation (MMP) or Top-Up (compensatory) system, the aim is either for the party's total number of representatives, including constituency representatives, to be proportional to its percentage of the party vote, or for the allocation of additional party seats to offset all or most of the disproportionate result in the constituencies. The party vote determines the proportional number of representatives the party has in the assembly, so creating a proportional representation, differently from the semi-proportional parallel voting.
  • Under a parallel voting or Supplementary Member (SUP or SM) system, the party seats are allocated proportionally within themselves, without consideration of any constituency seats the party may have won. Under some points of view, the SUP is not an electoral method, but two systems run in parallel for simultaneous, separate elections. However, differently from the Mixed member proportional representation, the proportional division of the seats between the contesting parties is calculated upon the party-list seats only, and not upon all seats.


  Calculation methods

At the regional or national level (i.e. above the constituency level) several different calculation methods have been used:

  • In the Welsh model of AMS, the regional seats are divided using a D'Hondt method. However, the number of seats already won in the local constituencies is taken into account in the calculations for the list seats, and the first average taken in account for each party follows the number of FPTP seats won.[1] Similar system are used in Scotland and London.



  Decoy lists



Decoy lists are not used in Scotland, Wales, or most other places using AMS, where most voters vote for candidates from parties with long-standing names. In the run up to the 2007 Scottish election, the Labour party had considered not fielding list candidates in the Glasgow, West of Scotland, and Central Scotland regions, as their constituency strength in the previous two elections had resulted in no list MSPs; instead they proposed to support a list composed of Co-Operative Party candidates; previously the Co-Operative party had chosen not to field candidates of its own but merely to endorse particular Labour candidates. However the Electoral Commission ruled that as membership of the Co-Operative party is dependent on membership of the Labour party they could not be considered distinct legal entites. In contrast, in the 2007 Welsh Assembly Election, Forward Wales had its candidates (including sitting leader John Marek) stand as independents, to attempt to gain list seats they would not be entitled to if Forward Wales candidates were elected to constituencies in the given region. However the ruse failed: Marek lost his seat in Wrexham and Forward Wales failed to qualify for any top-up seats.

Decoy lists would be technically useless in most mixed-member proportional voting models: there, because the proportional party vote is the sole to determine the final political result of the election, overhang seats would automatically compensate any effect of eventual decoy lists.


  Former use

  • From 1993 to 2005 in Italy:

  Proposed use

In 1976, the Hansard Society recommended that AMS in a form different from the German be used for UK parliamentary elections, but instead of using closed party lists, it proposed that seats be filled by the 'best runner-up' basis used by the German state of Baden-Wurttemberg, where the compensatory seats are filled by the party's defeated candidates who were the 'best near-winner' in each of the state's four regions. The system eventually adopted without that provision for elections to the Scottish Parliament, Welsh Assembly and London Assembly, but not for elections to the House of Commons.





In the parallel systems, even the largest party will elect members from the party list, so the top list positions are guaranteed seats. This system is found in emerging democracies like post-communist Russia, where new national parties were evolving, and the voting system was intended to foster them, while allowing local independent members to win local seats, many of whom then joined the winning party. It retains the plurality principle but has another paper to allow voting for a party rather than a candidate.

  Voter understanding

Some writers argue that AMS is difficult for voters to understand, and thus disenfranchises the very people it is meant to empower. There is some evidence that many Scottish voters did not understand the implications of the system at first. In the first election for Scotland's new Parliament, the majority of voters surveyed misunderstood some key aspects of the difference there between the "first" (constituency) vote and the "second" (regional list) vote; indeed in some ways the understanding worsened in the second election. The Arbuthnott Commission found references to first and second votes fuelled a misperception that the constituency vote should be a first preference and the regional vote a second one. That misperception was not helped by the Green Party's tactic of running only regional candidates and appealing for "second votes."

In Scotland, to deal with the misunderstanding between "first" and "second" votes, the ballot for the 2007 Scottish Parliament election was changed as recommended by the Arbuthnott Commission. The British government announced on 22 November 2006 that the two separate ballot papers used in the previous Scottish Parliament elections would be replaced for the elections in May 2007 by a single paper — with the left side listing the parties standing for election as regional MSPs and the right side the candidates standing as constituency MSPs.

Scottish Parliament Election Study 1999 and Scottish Social Attitudes Survey 2003  % answering correctly
Question (and correct response) 1999 2003
Average 45% 39%

However, the detailed results of the Scottish Social Attitudes Survey, 2003 (shown in the table above) show the confusion was about "first" and "second" votes, creating an average of 28% wrong answers.

  See also



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