Mixed member proportional representation, also termed mixed-member proportional voting and commonly abbreviated to MMP, is an 'additional member' voting system used to elect representatives to numerous legislatures around the world. MMP is similar to other forms of proportional representation (PR) in that the overall total of party members in the elected body is intended to mirror the overall proportion of votes received; it differs by including a set of members elected by geographic constituency who are deducted from the party totals so as to maintain overall proportionality. Therefore, the additional party seats are compensatory: they top up the local results. In Germany MMP is called "personalized proportional representation" as distinct from the PR system used before MMP superseded it.
In each constituency, the representative is chosen using a single winner method, typically first-past-the-post (that is, the candidate with the most votes, by plurality, wins).
In the German state of Baden-Wurttemberg there are no party lists. 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.
In Germany's Bundestag and the New Zealand House of Representatives the overhang seats remain. For example, in New Zealand's 2005 General Election the Māori Party won 2.1% of the Party Vote, entitling them to 3 seats in the House, but won 4 electorates, leaving an overhang of 1 seat, which results in a 121-member house. If the party vote for the Māori Party had been more in proportion with the constituency seats won, there would have more likely been a normal 120-member house.
In most German states the other parties also receive extra seats ("balance seats") to create full proportionality.
On the regional or national level (i.e. above the constituency level) several different calculation methods have been used:
A similar system was proposed by the Independent Commission in 1999, known as Alternative Vote plus (AV+). This would have involved the use of the Alternative Vote for electing members from single-member constituencies, and regional party lists. However, contrary to the Labour Party's earlier manifesto promises, there was not a referendum before the 2001 general election and the statement was not repeated.
The MMP system in use in the London Assembly would have been used for the other proposed regional assemblies of England, but this process has stalled since the No vote in the Northern England referendums in 2004.
A proposal to adopt MMP for elections to the Legislative Assembly of Prince Edward Island was defeated in a plebiscite there on November 28, 2005.
In 2007 the Citizens' Assembly on Electoral Reform in Ontario, Canada, also recommended the use of MMP in future elections to the Legislative Assembly of Ontario, with a ballot similar to New Zealand's. A binding referendum on the proposal, held in conjunction with the provincial election on 10 October 2007, saw it defeated.
Conversely, in New Zealand, some voters who preferred a large party have voted for the minor party's local candidate to ensure it qualifies for seats. In this case the tactic does not distort the outcome but makes it more proportional by bypassing the 5% threshold. In the former case it also ensures that votes are not wasted, but at the cost of giving the FDP more seats than CDU voters would really have preferred.
In terms of tactical voting, the vote for the constituency representative is normally much less important than the party vote in determining the overall result of an election; but in some cases a party may be so certain of winning seats in the constituency elections that it expects no extra seats in the proportional top-up. Some voters may therefore seek to get a double representation by voting tactically and splitting their votes, though this runs the risk of unintended consequences. This does not work in those German states which add "balance seats" since those systems maintain full proportionality even when a party wins too many constituency seats.
For instance in the 2001 Italian elections, the two main coalitions (the House of Freedoms and the Olive Tree) linked many of their constituency candidates to decoy lists (liste civetta) in the proportional parts, under the names Abolizione Scorporo and Paese Nuovo respectively, so that if they won constituencies then they would not reduce the number of proportional seats received by the coalitions. Between them, the two decoy lists won 360 of the 475 constituency seats, more than half of the 630 total number of seats, despite winning a combined total of less than 0.2% of the national proportional part of the vote. In the case of Forza Italia (part of the House of Freedoms), the tactic was so successful that it did not have enough candidates in the proportional part to receive as many seats as it in fact won, missing out on 12 seats.
Decoy lists are not used in Germany, the UK, New Zealand, or most other countries using MMP, where most voters vote for candidates from parties with long-standing names.
In New Zealand the party vote is the first vote. In Scotland, to deal with the misunderstanding between "first" and "second" votes, the ballot for the latest 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 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|
|You are allowed to vote for the same party on the first and second vote (True)||78%||64%|
|People are given two votes so that they can show their first and second preferences (False)||63%||48%|
|No candidate who stands in a constituency contest can be elected as a regional party list member (False)||43%||33%|
|Regional party list seats are allocated to try to make sure each party has as fair a share of seats as is possible (True)||31%||24% ?|
|The number of seats won by each party is decided by the number of first votes they get (False)||30%||42%|
|Unless a party wins at least 5% of the second vote, it is unlikely to win any regional party lists seats (True)||26%||25%|
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.