Mixed‐Member Electoral Systems: A Definition and Typology

Abstract

Abstract Mixed‐member electoral systems are described as a mixture of two principles of electoral system design: majoritarian systems, which usually have single‐seat districts with plurality rule and tend to give greater representation to the two parties that receive the most votes; and proportional systems, which have multi‐seat districts, usually with party lists, and typically produce parliamentary representation that largely mirrors the vote shares of multiple parties. In the prototype mixed‐member system, half the seats in a legislative chamber (the nominal tier) are elected in single‐seat districts and the other half (the list tier) are elected from party lists allocated by proportional representation; such systems come in a wide variety of options, with the most important choices involved being those of how seats and/or votes are linked between the two tiers. Defines mixed‐member electoral systems as a subset of the broader category of multiple‐tier electoral systems. The typology of systems outlined is arranged in three main sections: Mixed‐Member Systems as Variants of Multiple‐Tier Electoral Systems; Majoritarian or Proportional: Linkage Between Nominal and Tier Lists—mixed‐member majoritarian (MMM) and mixed‐member proportional (MMP) systems; and How MMM and MMP Systems Work: Simple Systems and Additional Variables—this section includes a table of mixed‐member systems in use around the world in 1999.