| A jointPolitics andEconomics series |
| Social choice andelectoral systems |
|---|
 |
Single vote -plurality methods |
By results of combination By mechanism of combination By ballot type |
 Mathematics portal |
Amixed single vote (MSV)[1] is a type ofballot inmixed-member electoral systems, where voters cast a single vote in an election, which is used both for electing a local candidate and as a vote for a party affiliated with that candidate according to the rules of theelectoral system. Unlike mostmixed proportional andmixed majoritarian systems (such asparallel voting) where voters cast two votes,split-ticket voting is not possible under MSV.[1] This significantly reduces the possibility of manipulatingcompensatory mixed systems,[2][3] at the price of reducing voter choice. An alternative based on the mixed single vote that still allows for indicating different preferences on different levels is themixed ballot, which functions as a preferential (mixed) single vote.
With MSV, voters usually cast their single vote for a local candidate in asingle-member district (SMD) and then all votes (or just thewasted votes, depending on the system) from this lower tier are added to distribute seats between upper tier candidates, typically nationalparty lists. Howproportional the outcome is depends on many factors including thevote transfer rules (which votes are recounted as party list votes), whether there is aseat linkage, and other parameters (e.g. the number of list seats) used in the system.[2] MSV systems originate fromGermany and variations are currently used inBolivia,Lesotho andHungary for local elections in larger municipalities.
MSV is distinct from a very similar balloting system ofopen list proportional representation where voters only vote for candidates (and this vote is then used as a party vote as well), as open list PR is generally not considered a mixed electoral system, therefore the term mixed single vote is not used for this type of system.
The mixed single vote has its origin in West Germany, where two different types of compensatory systems were developed at about the same time:
The third type of mixed single vote system is the single vote equivalent of parallel voting (sometimes called 'direct vote transfer'), which uses the same vote on both the majoritarian and proportional tiers. This makes such systemsnon-compensatory, falling under thesuperposition type of mixed systems identified by Massicotte & Blais.[4]
| Compensatory mixed systems | ||
|---|---|---|
| single vote systems (mixed single vote) | dual vote systems | |
| Seat linkage | top-up MSV
| mixed-member proportional representation (MMP) |
| additional member system (AMS) | ||
| alternative vote plus (AV+) | ||
| Hybrids: e.g. parallel voting+AMS (South Korea) | ||
| Vote linkage | positive vote transfer (PVT)
| Hybrids:
|
| mixed ballot transferable vote (MBTV) | ||
| Vote linkage and seat linkage | dual-member proportional (DMP) | Schulze MMP |
| Non-compensatory mixed systems | ||
| single vote systems | dual vote systems | |
| No linkage | mixed single vote, unlinked versions (MSV)
| parallel voting |
| Vote linkage | mixed single vote,superposition
| - |
Mixed single vote systems do not suffer from theticket-splitting manipulation problem as conventional dual vote compensatory systems do.[3] However, they also deny voters the possibility to express sincere different preferences on individual (local) candidates and party-list.
Seat linkage MSV systems, by default are not immune todecoy list strategies, but thisstrategic nomination is significantly less effective than in dual vote systems.[3] The positive vote transfer system (vote linkage MSV) is not vulnerable to decoy lists, but is also almost always less proportional. If the number of compensatory seats is (extraordinarily) high, vote linkage systems might incentivize parties to loose local elections[5] - but this was almost impossible in any vote transfer system implemented so far, which have relatively few compensatory seats. A certain type of (positive) vote transfer system may be vulnerable to the "stronghold split strategy", which aims to capture "surplus votes" like a system with winner compensation but this tactic has not been empirically documented.[3]
Mixed single vote systems can be used also with a seat linkage method to achieve effectivelylist PR with local representation (via plurality or majority). Such systems are fundamentallymixed-member proportional systems without the option of split ticket voting. This is the original version of MMP, where all votes, except for those in favour of independent candidates or parties below the entry threshold are transferred and used for the compensation mechanism.Germany, where the 1949 elections were held under a mixed single vote system that used plurality rule on the lower tier and was overall proportional on the regional (state) tier. The country subsequently changed the system to two-vote MMP.[1]
Countries that currently use such systems are:
Countries which previously used such systems:
Hungary: Local elections in municipalities and districts in thecapital with a population over 10 000 use a mixed single vote with positive vote transfer, where only votes for losing candidates are transferred to the compensatory tier.[7] The vote transfer takes place based on the party affiliation of the local candidates and seats are allocated proportionally based on the transferred votes.[8]
Since the2014 elections, General Assembly of Budapest also uses a mixed single vote, in that the 23 directly elected mayors of the districts and there are 9 members elected from compensation-lists of parties based on the votes cast for the mayoral candidates. (Budapest mayor candidates and district mayor candidates can be listed on compensation-lists)
Because of the comparatively few compensatory seats, the system does not guarantee proportional results and commonly underrepresents smaller parties, however theoretically, it could also underrepresent larger parties compared to alist PR system.
National Assembly elections use adifferent positive vote transfer system,[9] which also partially compensates winning candidates, however, that system is not a pure mixed single vote system as it also has aparallel voting component.
