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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 In Germany MMP is called "personalized proportional representation" as distinct from the PR system used before MMP superseded it.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 Quebec, where they are debating a proposed MMP model, it is called the 'compensatory mixed member' voting system

Procedures

The voter casts two votes: one for a constituency representative and one for a party (or, with open-list in Bavaria's state parliament election system, for one of the party's list candidates). If a candidate is on the party list, but wins a constituency seat, they do not receive two seats; they are instead crossed off the party list and replaced with the next candidate down. In the original variant used at first in Germany, still used by two States of Germany, both votes were combined into one, so that voting for a representative automatically means also voting for the representative's party. Most of Germany changed to the two-vote variant to make local MPs more personally accountable. In the 2005 New Zealand election, 20% of local MPs were elected from electorates which gave a different party a plurality of votes.

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.

Threshold

In order to be eligible for list seats in many MMP models, a party must earn at least a certain percentage of the total party vote, or no candidates will be elected from the party list. Candidates having won a constituency will still have won their seat. In Germany and New Zealand the threshold is 5%, in Bolivia 3%. A party can also be eligible for list seats if it wins at least three constituency seats in Germany, or at least one in New Zealand. Having a member with a 'safe' constituency seat is therefore a tremendous asset to a minor party in New Zealand. In almost all elections in the UK there are no thresholds except the "effective threshold" inherent in the regional structure. However the elections for the London Assembly have a threshold of 5% which has at times denied seats to the Christian People's Alliance (in the 2000 election), the British National Party and the Respect - The Unity Coalition (both in the 2004 election).

Ballot for electoral district 252, Würzburg, for the 2005 German federal election. Constituency vote on left, party list vote on right.

Overhang seats

Because a party can gain fewer seats by the party vote than needed to justify the won constituency seats, overhang seats can occur, though not in the British and Italian models which do not provide for overhang seats. There are two ways of dealing with overhang seats. Both raise the total number of seats.

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.

Calculation methods

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

• The total number of seats in the assembly are allocated to parties proportionally to the number of votes the party received in the party portion of the ballot. This can be done by the highest remainder method, the highest average method, or the Ste. Lague formula. Subtracted from each party's allocation is the number of constituency seats that party won, so that the additional seats are compensatory (top-up). In the British model, the highest averages method is used to allocate list seats. Again the number of seats already won in the constituencies is taken into account in the calculations for the list seats, but with no overhang seats.
• In the Italian model of MMP (used 1993-2005), for every constituency seat won by a party that party's vote total is reduced by the number of votes received by the second-place candidate in the constituency, subject to the condition that the deduction cannot be less than 25% of the total vote cast in the constituency, unless this would make the deduction larger than the number of votes received by the winning candidate, in which case that candidate's total vote is subtracted.

Use

MMP is currently in use in:

• Bolivia
  • Chamber of Deputies (Cámara de Diputados), the lower house
• Germany
  • Bundestag, the federal lower house
  • all state parliaments except Saarland, Bremen and Hamburg, but it is being introduced in Hamburg, see Hamburg Voting System.
• Italy, with the new Electoral System introduced in 2005¹
  • Camera dei Deputati, the lower house
  • Senato della Repubblica, the upper house
• Lesotho
  • National Assembly, the lower house
• New Zealand
  • House of Representatives, unicameral (see Electoral system of New Zealand)
• South Africa
  • Municipal elections
• United Kingdom
  • Scottish Parliament, unicameral
  • National Assembly for Wales, unicameral
  • London Assembly, unicameral
• Venezuela
  • National Assembly of Venezuela (Asamblea Nacional)
  • State Legislative Councils (Consejos Legislativos Estadales)

The unicameral National Assembly of Hungary has a complex voting system that results in a less proportional representation than MMP but more proportional than Parallel voting.

Proposals for use

United Kingdom

In 1976, the Hansard Society recommended that MMP 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. The system was eventually adopted without that provision in parts of Britain.

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.

Canada

In March 2004 the Law Commission of Canada proposed a system of MMP for the Canadian House of Commons [1] but that proposal has not been adopted.

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.

Potential for tactical voting

In systems with a threshold, tactical voting for a minor party that is predicted to poll slightly below the threshold is relatively common, especially by voters who are afraid that the minor party missing the threshold would weaken the larger political camp that the minor party belongs to. For example the German moderate-right Free Democratic Party (FDP) has often received votes from voters who preferred the larger Christian Democratic Union (CDU) party, because they feared that if the FDP received less than five percent of the votes, the conservative camp would be weakened so much that the CDU wouldn't be able to form a government. The FDP and other smaller parties campaigned to lower the threshold to the 4% used in Scandinavia and Austria, which might have succeeded except for the fear of resurgence of neo-nazi parties.

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 tactic 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. This tactic is not prevalent in good MMP models with enough extra seats: in Germany and the German states, generally 50% of the seats are "list seats," in Scotland 43%, in New Zealand 42.5%. Where there is a ratio of less than 30%, the model may be considered "MMP-lite." In Albania where they were only 28.6% of the total, this was so low that the two main parties expected no extra seats, and both started voting for allied minor parties with their party votes. This became so severe that it totally distorted the working of the model. Rather than increase the number of "list seats" or allow additional "overhang" seats, Albania recently decided to change to a pure-list system.

Decoy lists

Political parties can also abuse the system, if their electoral law lets them separate their party in two. One contests the constituency seats, the other contests for the list seats. This will produce an overhang. They can co-ordinate their campaign and work together within the legislature, while remaining legally separate entities. This can also give other advantages in areas such as party funding.

For instance in the 2001 Italian elections, one of the two main coalitions (the House of Freedoms, which opposed the MMP system, linked many of their constituency candidates to a decoy list (liste civetta) in the proportional parts, under the name Abolizione Scorporo. As a defensive move, the other coalition Olive Tree) felt obliged to do the same, under the name Paese Nuovo. If they won constituencies, this 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 places using MMP, where most voters vote for candidates from parties with long-standing names. In a model like Scotland's with eight separate regions, a major party would only want to run a decoy list in those regions where it was too strong to win list seats, but this would be impratical.

Voter understanding

Some writers argue that MMPR is difficult for voters to understand, and thus disenfranchises the very people it is meant to empower^{citation needed} There is some evidence that many Scottish voters did not understand the implications of the system. 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 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.

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

• List of democracy and elections-related topics
• Voting system
• Leveling seat

Further reading

• Malone, R. 2008. Rebalancing the Constitution: The Challenge of Government Law-Making under MMP. Institute of Policy Studies, Victoria University of Wellington: Wellington, New Zealand.
• Mudambi, R. and Navarra, P. 2004. Electoral Strategies in Mixed Systems of Representation. European Journal of Political Economy, Vol.20, No.1, pp. 227-253.
• Shugart, S. Matthew and Martin P. Wattenberg, (2000a), "Mixed-Member Electoral Systems: A Definition and Typology", in Shugart, S. Matthew and Martin P. Wattenberg (2000). Mixed-Member Electoral Systems: The Best of Both Worlds?" Oxford: Oxford University Press, pp. 9-24.
• Massicotte Louis and Andre Blais, (1999), "Mixed Electoral Systems: A Conceptual and Empirical Survey", Electoral Studies, Vol. 18, 341-366.

Notes

External links

• ACE Project: Germany, the cradle of MMPR
• A Handbook of Electoral System Design from International IDEA
• Electoral Design Reference Materials from the ACE Project
• Scottish Social Attitudes Survey, 2003.

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