Electoral Systems

… a core concept in Governance and Institutions and Atlas100

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Concept description

The ACE Electoral Knowledge Network (reference below, link on right) describes electoral systems as translating the votes cast in an election into results – the offices/seats – won by parties and candidates.

ACE notes that the key variables are:

  • the electoral formula used (i.e., whether a plurality/majority, proportional, mixed or other system is used, and what mathematical formula is used to calculate the seat allocation)
  • the ballot structure (i.e., whether the voter votes for a candidate or a party and whether the voter makes a single choice or expresses a series of preferences)
  • the district magnitude (not how many voters live in a district, but how many representatives to the legislature that district elects).
Guiding principles of electoral systems

ACE writes:

“When an electoral system is chosen there are a number of things this system can be asked to accomplish or at least be conducive to – a stable and efficient government, coherent coalitions and strong parties are only a few. These goals – and their order of priority – are likely to differ between the different stakeholders.

“In addition to this, there are general principles that can be used to guide the design of electoral system, as well as the process of choice itself. Some of the more important principles are:

  • Representation – The basic task for an electoral system is to translate votes into seats; to transform the expressed will of the voters into people who will represent it. There are many views of what fair representation is – geographic representation, descriptive representation, ideological or party political representation – but regardless of the view that is taken in each country, representation as a principle is a key guide when designing the most suitable electoral system.
  • Transparency – It is important that the mechanisms of the electoral system be as transparent as possible and known to both voters and political parties and candidates well in advance in order to avoid confusion and distrust in the results they produce at elections. In addition to this, the process through which the choice of electoral system is arrived at also benefits from transparency for the same reasons. If stakeholders’ arguments and influence over the process of review, reform or adoption are presented in an open way, the process and the electoral system arrived at will have a greater chance of being seen as legitimate.
  • Inclusiveness – The electoral system will have a greater chance of being accepted as fair and legitimate if it is considered to work in an inclusive manner. This means not only that the electoral law allows as many as possible citizens to vote (including inclusive suffrage, making sure that the system is easily understandable, and assuring access for all to the polling station), but also that the mechanisms of the electoral system do not overtly discriminate against any one group in society, minority or otherwise. Also, if the process through which the electoral system is arrived at is as inclusive as possible, both the process and the system may benefit as legitimacy and ownership increase, and as more stakeholders are able to bring suggestions and participate in the process of finding the most appropriate system for the society in question.
Systems analyzed by ACE

ACE provides a detailed description and commentary on 5 plurality/majority systems and 2 proportional representation systems.

ACE notes that the principle of plurality/majority systems is simple:

After votes have been cast and totalled, those candidates or parties with the most votes are declared the winners (there may also be additional conditions). However, the way this is achieved in practice varies widely. Five varieties of plurality/majority systems can be identified:

  • First Past The Post (FPTP),
  • Block Vote (BV),
  • Party Block Vote (PBV),
  • Alternative Vote (AV), and
  • the Two-Round System (TRS).

“In an FPTP system (sometimes known as a plurality single-member district system) the winner is the candidate with the most votes but not necessarily an absolute majority of the votes. When this system is used in multi-member districts, it becomes the Block Vote. Voters have as many votes as there are seats to be filled, and the highest-polling candidates fill the positions regardless of the percentage of the vote they achieve. This system – with the change that voters vote for party lists instead of individual candidates – becomes the Party Block Vote.

“Majoritarian systems, such as the Alternative Vote and the Two-Round System, try to ensure that the winning candidate receives an absolute majority (i.e., over 50 per cent). Each system in essence makes use of voters’ second preferences to produce a winner with an absolute majority if one does not emerge from the first round of voting.”

ACE describes the rationale behind proportional representation (PR) systems:

“The rationale underpinning all PR systems is to consciously reduce the disparity between a party’s share of the national vote and its share of the parliamentary seats; if a major party wins 40 per cent of the votes, it should win approximately 40 per cent of the seats, and a minor party with 10 per cent of the votes should also gain 10 per cent of the legislative seats. This congruity between a party’s share of the vote and its share of the seats provides an incentive for all parties to support and participate in the system.

“PR requires the use of electoral districts with more than one member: it is not possible to divide a single seat elected on a single occasion proportionally. There are two major types of PR system

  • List PR
  • Single Transferable Vote (STV)

“Proportionality is often seen as being best achieved by the use of party lists, where political parties present lists of candidates to the voters on a national or regional basis, but preferential voting can work equally well: the Single Transferable Vote, where voters rank-order candidates in multi-member districts, is another well-established proportional system.

“There are many important issues which can have a major impact on how a PR system works in practice. The greater the number of representatives to be elected from a district, the more proportional the electoral system will be. PR systems also differ in the range of choice given to the voter – whether the voter can choose between political parties, individual candidates, or both.”

Advantages and disadvantages of different electoral systems

ACE summarizes the advantages and disadvantages of five variations in its Table 7, reproduced below.

Atlas topic, subject, and course

Electoral Systems and Democratic Reform (core topic) in Governance and Institutions and Atlas100 Governance and Institutions.


ACE Electoral Knowledge Network, Electoral Systems, at http://aceproject.org/ace-en/topics/es/onePage, accessed 25 August 2016. The ACE article notes that it was Reproduced by permission of International IDEA from Electoral System Design: The New International IDEA Handbook © 2005 International Institute for Democracy and Electoral Assistance The electronic version of this publication is made available under a Creative Commons Attribute-NonCommercial-ShareAlike 3.0 (CC BY-NC-SA 3.0) licence.

Page created by: Ian Clark, last modified on 25 August 2016.

Image: ACE Electoral Knowledge Network, Electoral Systems, at http://aceproject.org/ace-en/topics/es/onePage, accessed 25 August 2016.