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Themixed ballot transferable vote (MBTV) refers to a type of vote linkage-basedmixed-memberelectoral system where a group of members are elected on local (lower) tier, for example insingle-member districts (SMDs). Other members are elected on a compensatory national (upper) tier from alist and voters cast a singleballot where they may indicate their preferences separately.[1]
A dual vote mixed system is not necessarily amixed ballot system, particularly the ones using separate ballots for the two votes. This article is primarily about systems using mixed ballots. For the dual vote, hybrid versions ofparallel voting andMSV used inHungary and formerly used inItaly for national elections, seescorporo.[2]
Unused votes from the lower tier are counted on the upper tier in a compensatory way using a (partial,positive) vote transfer mechanism. This tied, preferential nature of the dual ballot makes it different frommixed-member proportional (seat linkage compensatory) andparallel voting (non-compensatory) systems, which also use two votes for the two tiers. Howproportional the outcome is depends on among other factors, the rules (what counts as "wasted" vote) and parameters (e.g. the number of compensatory seats) used in the system.[3]
In Hungary, elections to theNational Assembly use a dual vote based positive vote transfer system,[4] where votes for candidates that did not win a seat are added along with excess votes for the winner in the seat to the list votes.[5] This has plurality SMDs and also partially compensates winning candidates, however, that system uses aparallel voting component to count list votes (which are located on separate ballots).
A system formerly used in Italy, scorporo is also a dual vote and vote linkage based mixed electoral system, but differs from MBTV in that it uses negative vote transfer as its compensatory mechanism compensation. These systems lack the "transferable" (preferential) part of MBTV, in favour of an automatic vote transfer based on party affiliation.
| Compensatory mixed systems | ||
|---|---|---|
| single vote systems | dual vote systems | |
| Seat linkage | mixed single vote, top-up versions (MSV)
| Two vote "top-up" - broadlymixed-member proportional representation (MMP)
|
| Hybrids: e.g. parallel voting+seat linkage compensation (South Korea) | ||
| dual-member mixed proportional (DMP) | ||
| Vote linkage | positive vote transfer
| Hybrids (parallel voting+vote linkage):
|
| Others systems: | ||
| mixed ballot transferable vote (MBTV) - preferential mixed single vote | ||
The simplest type of MBTV system allows two single choices on the ballot: one for a local candidate, one for a party list. This type of ballot is also used in theelectoral system of Germany[6] and New Zealand.
A ballot can allow either the voter to rank the candidates or the party lists or both, in this case rankings can be used for a system of elimination, like that ofinstant-runoff voting (to determine local winners and which parties pass the entry threshold). If ranking of both is allowed, the ballot design can also allow to intermix the rankings, providing afull ranking.[1]
The ranked ballots can also be used for elections bySTV on the local tier, an example is a proposal by Schulz,[7] where not only can voters rank parties intermixed with candidates on a local level, but another party vote can be cast for the MMP-type ofcompensation (seat linkage). The system utilizes the mixed ballot by providing that if a party has receivedoverhang seats, then only a certain share of those ballots which have contributed to the election candidates of that party will be considered when counting the party votes. The rest of those ballots are considered to have been cast for the party of those candidates who got elected, which avoidssplit ticket voters double voting power.
MBTV systems may be designed around other systems, for exampleapproval andproportional approval voting.
The German electoral system, which, while it falls under the category of MMP systems due to its seat linkage mechanism, also uses a mixed ballot on which the first vote (Erststimme) and second vote (Zweitstimme) are both single choice votes. In addition, as in MBTV, not all ballots are used in the compensatory tier, such namely ballots cast for independent candidates who have won a district seat and parties below the electoral threshold.[6] This mechanism makes it similar to the preferential interpretation of the mixed ballot when it would be used in a purely vote linkage based system.
