Overhang seat

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Overhang seats are constituency seats won in an election under the traditional mixed member proportional (MMP) system (as it originated in Germany), when a party's share of the nationwide votes would entitle it to fewer seats than the number of individual constituencies won.

How overhang seats arise[edit]

Under MMP, a party is entitled to a number of seats based on its share of the total vote. If a party's share entitles it to ten seats and its candidates win seven constituencies, it will be awarded three list seats, bringing it up to its required number. This only works, however, if the party's seat entitlement is not less than the number of constituencies it has won. If, for example, a party is entitled to five seats, but wins six constituencies, the sixth constituency seat is referred to as an overhang seat. Overhang can result from an unproportional distribution of constituencies.[1]

Earning overhang seats[edit]

The two mechanisms that together increase the number of overhang seats are:[2]

  1. winning many constituencies;
  2. decreasing the number of party votes and therefore the number of seats to which the party is proportionally entitled.

In many countries, overhang seats are rare – a party that is able to win constituency seats is generally able to win a significant portion of the party vote as well. There are, however, some circumstances in which overhang seats may arise relatively easily:

  • Few major parties, large number of minor parties – When there are only one or two major parties, but a relatively large number of minor parties that, combined, achieve a significant share of the total proportional vote, but fail to elect any constituency seats, the large parties often end up with overhang seats.
  • Similar lead across constituencies – If one party wins all or most constituencies of a relevant area with a rather low margin, it would be more prone to overhang mandates than if different parties lead in different constituencies, with the same overall share of each of the parties. As such, if there is less difference between constituencies, overhang seats are more probable.
  • A large number of constituencies compared with the total number of seats – If too many seats are used for constituencies, the remainder are less likely to ensure strict proportionality.
  • Unevenly sized constituencies – Candidates that win small constituencies by a narrow margin do not generate enough votes to justify their full seats under a proportional system.
  • Low turnout in some constituencies – This has the same effect as small constituencies. Furthermore, turnout and party preferences may be highly correlated, e.g. rural vs. urban areas.
  • Small number of seats to be allocated – The higher the absolute number of constituencies, the more likely it is that different reasons for overhang seats will balance out between parties. E.g., after the German federal Bundestag election in 2013, the main reason for overhang seats was that some compensation happens for party's state lists instead of at the federal level only.
  • Individual candidates with strong local followings – Sometimes, a particular politician will have strong support in their own constituency, but will belong to a party with very low support, even in their own area. The candidate will be elected based on their own qualities, but the party they belong to will not receive enough votes to justify the candidate's seat. In the case of independent candidates, this is usually guaranteed – they have no party at all, and so obviously cannot win votes under MMP's party-list proportional representation. However, some countries, such as New Zealand, have special rules dealing with independents – seats won by these candidates are exempted from the proportional system altogether.
  • Regional parties – Parties based in a particular region may win a substantial number of constituency seats in that region without necessarily gaining a large share of the national vote. Parties focused on particular ethnic or religions minorities may also come under this category, particularly if seats are reserved for these groups.
  • Tactical voting – Voters in countries such as Germany may cast two votes and they need not be for the same party. A voter might support one party in the list vote but vote for the candidate of another party in the local vote, perhaps because the former party lacks a candidate in his or her constituency or it has a candidate but he or she has little chance of winning. Parties that win many local seats but attract a reduced list vote may receive an overhang as a result.
  • Decoy parties – Party labels in the constituencies can be deliberately mismatched with those in the proportional vote in an attempt to induce tactical voting. In Italy in 2001, two lists won a significant majority of the total number of first-past-the post seats, despite winning almost none of the proportional vote. The system, nicknamed scorporo, was not a type of additional member system in which overhangs could occur, it resulted in a significant distortion to the desired compensatory nature.

Dealing with overhang seats[edit]

Overhang seats are dealt with in different ways by different systems.

Take the number of additional list seats off from the other parties' proportional entitlement[edit]

A party is allowed to keep any overhang seats it wins, and the corresponding number of list seats allocated to other parties is eliminated to maintain the number of assembly seats. This means that a party with overhang seats has more seats than its entitlement, and other parties have fewer. This approach is used in the Chamber of Deputies of Bolivia and the National Assembly of Lesotho. It was unsuccessfully recommended by the 2006 Ontario Citizens' Assembly on Electoral Reform for adoption by the Legislative Assembly of Ontario, and the proposed Dual-member proportional representation system uses this approach as well. While for the first additional list seats are simply denied to parties, in the latter three cases[specify], a fairer procedure was proposed of subtracting the constituency seats won by parties with overhang seats from the total number of seats and recalculating the quota (the largest remainder method was also recommended) to proportionally redistribute the list seats to the other parties.

Allow the overhang[edit]

A party is allowed to keep any overhang seats it wins, but other parties are still awarded the same number of seats that they are entitled to. This means that a party with overhang seats has more seats than its entitlement. The New Zealand Parliament uses this system; one extra seat was added in the 2005 election and 2011 election, and two extra seats in the 2008 election. This system was also used in the German Bundestag until 2013, when Germany switched to a fully compensatory system.

Other parties may be given additional list seats (sometimes called "balance seats" or leveling seats) lest they be disadvantaged. This preserves the same ratio between parties as was established in the election. It also increases the size of the legislature, as overhang seats are added, and there may also be extra list seats added to counteract them. This system results is less proportional than full compensation, as the party with the overhang is still receiving a "bonus" above its proportional entitlement. After the Federal Constitutional Court of Germany ruled in 2008 that the established implementation of Option 1 was unconstitutional (because in rare instances, it allowed votes to negatively affect the number of seats for a given party, contradicting the voter's will), full compensation of overhang seats is applied as of 2013 in the German Bundestag by providing for the first time for the creation of balancing seats.

Non-awarding of overhang seats[edit]

A party is not allowed to keep any overhang seats it wins, with its number of seats actually being reduced until it fits the party's entitlement. This method raises the question of which constituency seats the party is not allowed to keep. After that is determined, it would then have to be decided who, if any, will represent these constituencies. This was used in the Landtag of Bavaria until 1966, with the candidates with the lowest number of votes don't keep the constituency seat. In the 1954 election two overhang seats were not awarded.


In New Zealand, the Māori Party won one overhang seat in 2005 and 2011, and two overhang seats in 2008.[3] In 2005 their share of the party vote was under 2% on the initial election night count, but was 2.12% in the final count which included special votes cast outside the electorate. On election night it appeared that the party, whose candidates had won four electorate seats, would get two overhang seats in Parliament. However, with their party vote above 2% the party got an extra seat and hence needed only one overhang seat. National got one less list seat in the final count, so then conceded defeat (the result was close between the two largest parties, National and Labour).

In state and federal elections in Germany, every constituency seat is granted[a] while the electoral system requires that a party needs 5% of the party-list vote to win list seats. Unless in federal elections a party wins at least three constituency seats, it is excluded by (i.e., due to) the election threshold. In 1994 the PDS fell below the 5% threshold but still got its share of list seats as it had won enough constituency seats, and the same happened in 2021 for Die Linke. But in 2002 the PDS won only two constituencies and was excluded from the list seats resulting in two overhang seats. The PDS had won four seats in Berlin at the 1998 election (in addition to surpassing the electoral threshold at 5.1% of the second vote) but - partly due to redistricting, which changed the boundaries of constituencies the PDS had won in 1998, lost two of their constituency seats, including placing third behind Hans-Christian Ströbele in the newly created Berlin Friedrichshain-Kreuzberg – Prenzlauer Berg East constituency.[b][4]

See also[edit]


  1. ^ With the exception of Bavaria, there to win a constituency seat 5% of the votes in the state for the party is needed.
  2. ^ the PDS had won the predecessor district de:Bundestagswahlkreis Berlin-Mitte – Prenzlauer Berg in 1994 and 1998; they also lost the redistricted and renamed Berlin Pankow constituency to Wolfgang Thierse


  1. ^ "Reasons for overhang seats". www.wahlrecht.de. Retrieved 14 June 2021.
  2. ^ "Handling Overhang Seats". www.wahlrecht.de. Retrieved 14 June 2021.
  3. ^ Green, Antony (22 September 2017). "New Zealand election guide". ABC News. Retrieved 14 June 2021.
  4. ^ https://www.spiegel.de/politik/deutschland/wahlkreisreform-die-geschleiften-pds-hochburgen-a-213969.html