Mixed ballot transferable vote

The mixed ballot transferable vote (MBTV) refers to a type of vote linkage-based mixed-member electoral system where a group of members are elected on local (lower) tier, for example in single-member districts (SMDs). Other members are elected on a compensatory national (upper) tier from a list and voters cast a single ballot where they may indicate their preferences separately.^[1]

Overview

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 from mixed-member proportional (seat linkage compensatory) and parallel voting (non-compensatory) systems, which also use two votes for the two tiers. How proportional 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.^[2] A hybrid version of the vote transfer, dual vote combination is used in Hungary for national elections.^[3]

In the table below, it can be seen that 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.

	(mixed) single vote	(mixed) dual vote
Seat linkage	MSV (top-up)	MMP AMS AV+
Vote linkage	MSV (positive vote transfer) DMP	Hybrids (MSV combined with parallel voting): Positive vote transfer: the Hungarian system Negative vote transfer: the Italian system (Scorporo) MBTV

Variations

Plurality

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 the electoral system of Germany.^[4]

Ranking

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 of instant-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, this version is called Full Ranking MBTV.^[1]

Other

MBTV systems could be designed around other systems, for example approval and proportional approval voting.

Usage

In Hungary, elections to the National Assembly use a dual vote based positive vote transfer system,^[5] which has plurality SMDs and also partially compensates winning candidates, however, that system uses a parallel voting component to count list votes.

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, certain 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.^[4] 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.

References

^ ^a ^b https://doi.org/10.13140/RG.2.2.15129.34407 Electoral incentives and the equal value of ballots in vote transfer systems with positive winner compensation
^ Golosov (2013). "The Case for Mixed Single Vote Electoral Systems". The Journal of Social, Political, and Economic Studies.
^ Political Capital (2012). "The New Electoral Law in Hungary — In-depth Analysis" (PDF).{{cite web}}: CS1 maint: url-status (link)
^ ^a ^b "Federal Elections Act, as last amended by Article 2 of the Act of 3 June 2021" (PDF). 3 June 2021.{{cite web}}: CS1 maint: url-status (link)
^ "2011. évi CCIII. törvény az országgyűlési képviselők választásáról" [Act CCIII. of 2011. on the election of members of the National Assembly] (in Hungarian).{{cite web}}: CS1 maint: url-status (link)