Overhang Seat - Two Mechanisms To Earn Many Overhang Seats

Two Mechanisms To Earn Many Overhang Seats

The two mechanisms that together increase the number of overhang seats are

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.
• 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 don't 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 constituencies — 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., in Germany the almost sole reason for overhang seats is the fact that compensation happens at the state level instead of the federal level.
• 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.