Mixed-member proportional representation

Part of the Politics series
Electoral systems
Single-winner/majoritarian Plurality First-past-the-post Plurality at-large (plurality block voting) General ticket (party block voting) Multi-round voting Two-round Exhaustive ballot Primary election Nonpartisan unified top-four Majority at-large (two-round block voting) Ranked / preferential systems Instant-runoff (alternative vote) Contingent vote Coombs' method Condorcet methods (Copeland's, Dodgson's, Kemeny–Young, Minimax, Nanson's, ranked pairs, Schulze, Alternative Smith) Positional voting (Borda count, Nauru/Dowdall method) Bucklin voting Oklahoma primary electoral system Preferential block voting Cardinal / graded systems Score voting Approval voting Combined approval voting Unified primary Usual judgment Satisfaction approval voting Majority judgment STAR voting
Proportional representation Party-list Electoral list open list closed list local lists Apportionment Sainte-Laguë D'Hondt Huntington–Hill Hare Droop Imperiali Hagenbach-Bischoff National remnant Highest averages Largest remainder Proportional forms of ranked voting Single transferable vote Gregory Wright Schulze STV CPO-STV Ranked party list PR Spare vote Proportional forms of cardinal voting Proportional approval voting Sequential proportional approval voting Method of Equal Shares Phragmen's voting rules Biproportional apportionment Fair majority voting Weighted voting Direct representation Interactive representation Liquid democracy
Mixed systems By type of representation Mixed-member majoritarian Mixed-member proportional Non-compensatory mixed systems Parallel voting Majority bonus Compensatory mixed systems Additional member system Mixed single vote (positive vote transfer) Scorporo (negative vote transfer) Mixed ballot transferable vote Alternative Vote Plus Dual-member proportional Rural–urban proportional
Other systems and related theory Semi-proportional representation Single non-transferable vote Limited voting Cumulative voting Binomial voting Other systems Multiple non-transferable vote Double simultaneous vote Proxy voting Delegated voting Indirect STV Liquid democracy Random selection (sortition, random ballot) Supermajority Social choice theory Arrow's theorem Gibbard–Satterthwaite theorem Public choice theory Veto Players List of electoral systems List of electoral systems by country Comparison of electoral systems Effects of electoral systems Political fragmentation Political efficacy Voter turnout
Politics portal
v t e

Mixed-member proportional representation (MMP or MMPR) is a mixed electoral system which combines local majoritarian elections with a compensatory tier of party list votes, which are used to allocate additional members in a way that aims to produce proportional representation overall. In most MMP systems, voters get two votes: one to decide the representative for their single-seat constituency, and one for a political party. Some countries use single vote variants of MMP, although this article focuses primarily on dual vote versions of MMP.

Seats in the legislature are filled first by the successful constituency candidates, and second, by party candidates based on the percentage of nationwide or region-wide votes that each party received.^[1][2][3] The constituency representatives are usually elected using first-past-the-post voting (FPTP). The nationwide or regional party representatives are, in most jurisdictions, drawn from published party lists, similar to party-list proportional representation. To gain a nationwide representative, parties may be required to achieve a minimum number of constituency seats, a minimum percentage of the nationwide party vote, or both.

MMP differs from parallel voting in that the nationwide seats are allocated to political parties in a compensatory manner in order to achieve proportional election results. Under MMP, two parties that each receive 25% of the votes end up with about 25% of the seats, even if one party wins more constituency seats than the other. Depending on the exact system implemented in a country and the results of a particular election, the proportionality of an election may vary.^[4] Overhang seats may reduce the proportionality of the system, although this can be compensated for by allocating additional party list seats to cover any proportionality gap.^[5]

MMP was first used to elect representatives to the German Bundestag, and has been adopted by New Zealand and others, with modifications.