 | This article includes a list ofgeneral references, butit lacks sufficient correspondinginline citations. Please help toimprove this article byintroducing more precise citations.(July 2018) (Learn how and when to remove this message) |
| A jointPolitics andEconomics series |
| Social choice andelectoral systems |
|---|
 |
By results of combination By mechanism of combination By ballot type |
 Mathematics portal |
Overhang seats are constituency seats won in an election under the traditionalmixed-member proportional (MMP) system (as it originated inGermany), when a party's share of the nationwide votes would entitle it to fewer seats than the number of individualconstituencies won.
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 greater 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 typically results from thewinner-take-all tendency ofsingle-member districts, or if the geographic distribution of parties allows one to win many seats with few votes.[1]
The two mechanisms that together increase the number of overhang seats are:[2]
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:
Overhang seats are dealt with in different ways by different systems.
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 theChamber of Deputies of Bolivia and theNational Assembly of Lesotho. It was unsuccessfully recommended by the 2006Ontario Citizens' Assembly on Electoral Reform for adoption by theLegislative Assembly of Ontario, and the proposedDual-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 (thelargest remainder method was also recommended) to proportionally redistribute the list seats to the other parties.
In theScottish Parliament,Welsh Senedd andLondon Assembly, the effect is similar, but the mechanism different. In the allocation of second vote list seats using ahighest averages method, the first vote constituency seats already won are taken into account when calculating party averages, with the aim of making the overall result proportional. If a party wins more seats in the first vote than its proportion of second votes would suggest it should win overall, or if an independent candidate wins a constituency seat, then the automatic effect is to reduce the overall number of seats won by other parties below what they might expect proportionally.
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. TheNew Zealand Parliament uses this system;[3] one extra seat was added in the2005 election and2011 election, and two extra seats in the2008 election. This system was also used in theGerman Bundestag until 2013.
Other parties may be given additional list seats (sometimes called "balance seats" orleveling 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. The result of this system 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 allowing uncompensated overhang seats 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),leveling seats were introduced for the2013 election and also used in those of2017 and2021.
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 theLandtag of Bavaria until 1966, with the candidates with the lowest number of votes not keeping the constituency seat.
The system is now also in place at the federal level in Germany, having commenced with the2025 German federal election. As with the previous system in Bavaria, overhanging constituency winners are excluded in order of lowest vote share.[4]
Prior toGerman reunification, overhang mandates - particularly at the federal level - were relatively rare and never amounted to more than five (out of over 400 total seats) in any given Bundestag and several federal elections resulted in no overhang at all.[5] This was in part due to the relative strength of the two major parties,CDU/CSU andSPD; with both parties winning large shares of the vote in the pre-reunification three-party system, it was rare for either to win more than a handful of overhanging constituencies.[6][7]
However, this began to change asEast Germany started participating in German federal elections starting with the1990 German federal election, with thePDS posting particularly strong results in those states. This, along with the rise ofAlliance '90/The Greens, served to depress the party-list vote shares, creating more overhang seats than in prior elections.
In the1994 German federal election, the re-electedKohl government supported by a "black-yellow" coalition (CDU/CSU andFDP) achieved a relatively slim majority of 341 out of 672 seats to the opposition's (SPD,Alliance 90/The Greens, PDS) 331 seats at the opening session. This majority would have been even narrower if not for twelve overhang seats the CDU/CSU had achieved, which were however partially mitigated by the four overhang seats for the SPD.[8] This led to much more public debate on the existence of overhang seats and what to do about them.[9][10][11][12] There was even a challenge of the validity of the election result based on the overhang seat issue raised by a private citizen after the 1994 election, which was however dismissed as "obviously without merit".[13]
The problem thus turning from a theoretical consideration to a real issue, theGerman Constitutional Court as early as 1997 ruled that a "substantial number" of overhang mandates which weren't equalized throughleveling seats were unconstitutional.[14] The issue became more pressing after a particularly notorious case ofnegative vote weight at the2005 election. The election in theDresden I constituency was held two weeks later than the other 298 constituencies after the death of a candidate.Der Spiegel published an article in the intervening time outlining how more votes for the CDU could lead to them losing an overhang seat, and thus narrowing their plurality in the close election.[15] The anticipatedtactical voting in Dresden I did occur asAndreas Lämmel (CDU) won the constituency with roughly 37% of the constituency vote while his party won only 24.4% of the party-list vote, with the FDP receiving 16.6% - more than one and a half times their federal vote share of 9.8%.[16]
This led to another ruling by theGerman Constitutional Court in 2008 which ruled that the existing federal electoral law was unconstitutional in part as it violated the principle ofone person one vote and produced an overly opaque relationship between the numbers of votes cast and seats in parliament.[17][18][19][20] However, the Court also allowed for a three year deadline to change the electoral law, allowing for the2009 German federal election to be held under the previous set of rules.
The electoral reform passed with the votes of the governing "black-yellow" coalition in late 2011 (a few weeks after the deadline set in 2008) - and without consulting the opposition parties - was again ruled unconstitutional by the Constitutional Court.[21][18] Furthermore, the Court clarified that the federal electoral system was supposed to be primarily one ofproportional representation and a number of non-compensated overhang seats above 15 would "dilute" this proportional character.[22][23]
As the Bundestag thus lacked a constitutional electoral mechanism[24] and the2013 German federal election was coming up, the government agreed to negotiations with the opposition parties, leading to a new electoral law being passed in early 2013 with broad support from all parties in the Bundestag except Die Linke.[25] This addedleveling seats and was used in the 2013, 2017 and 2021 elections.
On the state level, an unclear wording in the state electoral law ofSchleswig-Holstein led to different possible assignments of leveling seats to equalize the overhang seats ultimately resulting in the2009 Schleswig-Holstein state election giving a majority of seats to thePeter Harry Carstensen led "black-yellow" coalition, despite them having won a lower share of the vote than the SPD, Greens, Left,SSW opposition. Following a suit before the State Constitutional Court brought by opposition parties,[26] it was ruled that the electoral law in its then current interpretation did indeed violate thestate constitution but that the Landtag was to keep its composition until a new electoral law could be passed (which happened in 2011) after which new elections would be scheduled with enough time forcampaigns setting the next election for2012, two years earlier than if the Landtag had served its full five year term.[27]
The 2023 reform which eliminated the awarding of all overhang and leveling seats was also subject to a constitutional challenge. The Federal Constitutional Court upheld this part of the law.[28]
In the system used inGermany until the2025 election, every constituency seat won by any party or an independent is granted, while the electoral system requires that a party needs 5% of the party-list vote to win list seats. If a party wins at least three constituency seats, it is granted full proportional representation as if it passed the 5%electoral threshold, even if it did not. The awarding of overhang seats and theleveling seats required to compensate for this led to a drastic increase in the size of theBundestag beyond its normal size of 598 members.
In the2021 federal election,The Left fell just short of theelection threshold with 4.9% of the national vote but won threesingle-member constituency seats.[29] This entitled them to proportional representation in the Bundestag according to their second votes.[30] The extra compensation seats for other parties meant that the Bundestag would be the largest in German history, and in fact the largest freely elected parliament in the world, with 736MPs.[31]
In 2023, in response to the increasing size of the Bundestag, theScholz cabinet passed a reform law to fix the size of future Bundestags at 630 members beginning with the 2025 election. This is achieved by eliminating all overhang and leveling seats. A party's total number of seats will be determined solely by its share of party-list votes (Zweitstimmendeckung, "second vote coverage"). If a party wins overhanging constituency seats in a state, its constituency winners in excess of its share of seats would be excluded from the Bundestag in order of those that received the smallest vote shares. The rule allowing any party winning three constituency seats to receive full proportional representation was originally also abolished. The Federal Constitutional Court, however, decided that a 5% electoral threshold with no exceptions was unconstitutional and the rule was restored on an interim basis for the 2025 election.[28]
InNew Zealand,Te Pāti Māori (the Māori Party) usually gets less than 5% of the party votes, the threshold required to enter parliament – unless the party wins anelectorate seat. Te Pāti Māori won one overhang seat in2005 and2011, and two overhang seats in2008.[32] 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 andLabour). Te Pāti Māori won six electorate seats in2023, two more than its 3.08% share of the party vote entitled it to; and shortly after the general election, thePort Waikato by-election resulted in a further overhang seat for National.[33]
