Additional Member System

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The Additional Member System (AMS), also known as mixed-member proportional representation (MMP) outside of the United Kingdom[1][2][3][4] is a hybrid two-tier mixed-member system which varies in proportionality.

The term AMS is used in Scotland, Wales, and the London Assembly.

Method of voting[edit]


Voters are not required to vote for the same party in the constituency and regional votes. If a voter votes for different parties at the constituency and regional levels this is referred to as split-ticket voting. In the regional vote, the voter votes for a specific party, but has no control over which candidates from the party are elected. On the other hand, in the constituency vote, the voter votes for a specific candidate rather than a party. The Arbuthnott Commission recommended that Scotland change to a model where the voter can vote for a specific regional candidate as well, but this has not been implemented. With a similar model in Bavaria the second vote is not simply for the party but for one of the candidates on the party's regional list and both votes count for party and candidates so that every vote counts: Bavaria uses seven regions for this purpose. In Baden-Württemberg there are no lists; they use the "best near-winner" method in a four-region model, where the regional members are the local candidates of the under-represented party in that region who received the most votes in their local constituency without being elected in it, but this model has not been copied in the United Kingdom.


In the model of AMS used in the United Kingdom, 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.[clarification needed][5] Similar systems are used in Wales and London.





Decoy lists[edit]





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


AMS is used in:

It was used from 1993 to 2005 in Italy:






Scottish Parliament Election Study 1999 and Scottish Social Attitudes Survey 2003[7]
 % answering correctly
Question (and correct response) 1999 2003
Average 45% 37%

The system was implemented for the Scottish Parliament in order to make it difficult for one party to win an outright majority.[8] However, in 2011, the Scottish National Party won 69 seats, a majority of four.[citation needed]

There is some evidence that many Scottish voters did not understand the implications of the system at first.[citation needed] 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 misconception that the constituency vote should be a first preference and the regional vote a second one. That misconception was not helped by the Green Party's tactic of running only regional candidates and appealing for "second votes".[citation needed]


See also[edit]


  2. ^ "Elections in Wales". Cardiff University. 
  3. ^ "Electoral Reform and Voting Systems". 
  4. ^ "Mixed Member Proportional (MMP) System" (PDF). 
  5. ^ The National Assembly for Wales Archived January 9, 2009, at the Wayback Machine.
  6. ^ Report of the Hansard Society Commission on Electoral Reform Archived October 31, 2015, at the Wayback Machine., Hansard Society, 1976
  7. ^ Catherine Bromley; John Curtice; David McCrone; Alison Park (2006-07-04). Has Devolution Delivered?. Edinburgh University Press. p. 126. ISBN 0748627014. Proportion of respondents giving correct answers to knowledge quiz about the electoral system 
  8. ^ "Parliament in depth: Electoral System: Electoral system for the Scottish Parliament". Scottish Parliament. Archived from the original on 29 November 2014. Retrieved 23 November 2014.