Proportional Representation Voting Systems

Proportional representation voting systems facilitate the election of legislatures that accurately reflect the diversity of opinion of the electorate and tend to produce policy that adheres more closely to the "will of the majority" because more people have representation. At the same time, governance can be more complicated and geographic representation less certain than with winner-take-all elections.

Proportional representation (PR) voting systems provide representation to groupings of like-minded voters in proportion to their voting strength. If a grouping of voters -- either a political party, or a community of interest in a nonpartisan election -- wins 20 percent of the popular vote in an election for ten seats, these voters will win two of the ten seats. Sixty percent of the popular vote will win six of ten seats, and so on. Most of the world’s established democracies use some form of PR to elect their most powerful legislative body (The International IDEA Handbook of Electoral Design, p. 20-21).

PR voting systems facilitate the election of legislatures that more accurately represent both the ideological and demographic diversity of a population. They aim to realize the goals of majority rule and full representation. There are many different variants of PR, each with their advantages and disadvantages, as detailed in other factsheets. But all PR systems share two attributes:

  1. Multi-seat districts. PR requires districts that elect two or more representatives to a legislature. The number of representatives per district range from two (in Chile) to more than 400 (in South Africa, where the whole country acts as a single district). Some PR systems use a mix of one-seat districts and multi-seat districts.
  2. Lower "victory threshold." PR systems lower the victory threshold (percentage of votes needed to win a seat) anywhere from 33 percent (in a two-seat district) to less than 1 percent. For instance, in a 3-seat district elected by PR, a candidate needs a little more than 25% of the vote to win. By lowering the victory threshold, PR systems facilitate full representation and majority rule.

Beyond these two factors, however, the various PR systems diverge, each presenting their own advantages and disadvantages. The three main categories of PR are Party-List Systems, Mixed-Member Systems (also known as Additional Member Systems) and Modified At-Large Voting systems, which can be used for candidate-based or nonpartisan elections.

Arguments for and against PR systems stem from these systems’ tendency to elect legislatures that more fairly represent the range of voters in a jurisdiction. PR supporters argue that this fairer representation better ensures that a legislative majority is grounded in a popular majority. It better provides for full representation of the electorate, with a more accurate reflection of the demographic composition of the population, with greater representation of women, racial and political minorities and socio-economic classes than is typical in legislatures elected by winner-take-all systems. Furthermore, PR systems tend to result in higher voter turnout, as more viable candidates run from across the political spectrum and mobilize their supporters.

Opponents of PR argue that the fairer representation it provides in fact can empower extremist groups, can promote single-issue candidates and parties and can lead to unstable coalition government in party-based systems. They also warn against excessive influence of party leaders (particularly in party list forms of PR) and the dilution of geographic representation. (Please see relevant factsheets for in-depth discussions of the arguments for and against proportional voting systems.)

This factsheet is part of the CVD Factbook Series, a compilation of one-page factsheets covering voting systems and voting system reforms.