A family of electoral systems designed so that parties win legislative seats roughly in proportion to the votes they receive, usually through multi-member districts or a compensatory tier.
In more detail
Main forms are party-list systems, the single transferable vote and mixed-member proportional systems. District size and legal thresholds largely determine how proportional the result is. Duverger's hypothesis holds that plurality voting favours two-party competition while proportional systems support more parties; supporters stress fairer representation, critics stress coalition bargaining and weaker voter control over which government forms.