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. This article is primarily about systems using mixed ballots, for the dual vote, hybrid versions of parallel voting and MSV used in Hungary and formerly used in Italy for national elections see Scorporo. 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. In Hungary, elections to the National Assembly use a dual vote based positive vote transfer system, 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. This has plurality SMDs and also partially compensates winning candidates, however, that system uses a parallel 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. The simplest type of MBTV system allows two single choices on the ballot: one for a local candidate, one for a party list.