Mixed-member proportional representation

An electoral system that elects representatives in local districts and allocates additional party-list seats to make each party’s total seat share more closely match its vote share.

Party-list proportional representation: An electoral system that allocates legislative seats to parties in proportion to their vote totals. Its list-seat allocation supplies the compensatory tier in mixed-member proportional systems.
Parallel voting: An electoral system in which district and party-list seats are allocated independently rather than compensating for one another. It combines the same broad seat types without correcting the district tier’s disproportionality.
New Zealand electoral system: The electoral arrangements used to elect New Zealand’s national Parliament. New Zealand adopted mixed-member proportional representation for parliamentary elections beginning in 1996.
Proportional representation: A family of electoral systems designed to make elected-seat shares correspond closely to vote shares. Mixed-member proportional representation is one method within this broader family.
Single-member district: An electoral district that elects one representative. Each district elects a local representative, usually through a separate candidate vote.
First-past-the-post: A voting rule that elects the candidate with the most votes in each single-member district. It commonly fills the district tier but does not itself make overall party representation proportional.
German electoral system: The electoral arrangements used to elect Germany’s federal Bundestag. Germany’s federal elections are a prominent, long-running implementation of compensatory mixed-member representation.
Disproportionality: The mismatch between parties’ shares of votes and their shares of legislative seats. Compensatory seats are intended to reduce this mismatch in the overall result.
Overhang seat: A seat retained when a party wins more district seats than its proportional entitlement would otherwise allow. District victories can exceed a party’s list-based entitlement, complicating proportional seat totals.
Single transferable vote: A preferential voting system that elects multiple representatives per district using ranked ballots and vote transfers. It can produce proportional outcomes through multi-member districts rather than compensatory party lists.

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