Difference between revisions of "Category:Voting methods"

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Voting systems are also known as election methods.
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'''Voting systems''' or '''election methods''' are methods for groups of people to select one or more options from many, taking into account the individual preferences of the group members.  Voting is often seen as the defining feature of democracy, and is best known for its use in elections — but it can also be used to award prizes, to select between different plans of action, or as a means for computer programs to evaluate which solution is best for a complex problem.
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A key property of voting systems is that, because they are algorithms, they must be formally defined.  Consensus, for example, which is sometimes put forward as a voting system, is more properly a broad way of working with others, analogous to democracy or anarchy.
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== Aspects of voting systems ==
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=== The ballot ===
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''See: [[:Category:Ballot type|Ballot type]]''
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Different voting systems have different forms for allowing the individual to express their [[tolerances versus preferences|tolerances or preferences]].  In [[ranked ballot]] or "preference" voting systems, like [[Instant-runoff voting]], the [[Borda count]], or a [[Condorcet method]], voters order the list of options from most to least preferred.  In [[range voting]], voters rate each option separately.  In [[first-past-the-post]] (also known as plurality voting), voters select only one option, while in [[approval voting]], they can select as many as they want.  In voting systems that allow [[plumping]], like [[cumulative voting]], voters may vote for the same candidate multiple times.
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=== District (constituency) size ===
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A voting system may select only one option (usually a candidate, but also an option that represents a decision), in which case it is called a "single winner system", or it may select multiple options, for example candidates to fill an assembly or alternative possible decisions on the measure the ballot posed.
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Some countries, like Israel, fill their entire parliament using a single multiple-winner district ([[constituency]]), while others, like Ireland or Belgium, break up their national elections into smaller, multiple-winner districts, and yet others, like the United States or the United Kingdom, hold only single-winner elections.  Some systems, like the [[Additional member system]], embed smaller districts within larger ones.
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=== Party-list systems ===
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In [[party-list proportional representation]] systems, candidates can be aligned with, or nominated by, parties, and the party's list of candidates plays a functional role within the system.  These parties may in turn be aligned with other parties, to form [[coalition]]s, which can play roles beyond those played by the party.  These systems are designed to ensure [[proportional representation]], the idea that the candidates selected from a given party (or, in non-party-list systems, informal grouping) should be in proportion to the votes cast for that party.  Some of these systems, however, have [[election threshold]]s--minimum numbers of votes cast for a party to win any seats.  The purpose of an election threshold is generally to keep very small parties from participating in a parliament, in order to maintain stability of governments.
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=== None of the above option===
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In some voting systems, voters may choose to select none of the candidates (or poll options), by voting for a "None of the above" option. If this option wins, the election fails, all candidates or poll options are excluded from a subsequent election.
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=== Write-in candidate - poll option ===
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Some elections allow voters to write in the name of a person (or of the poll option) not on the ballot as their candidate (or as a poll option). Write-in candidates (poll options) rarely win and votes are often cast for ineligible people or fictional characters. This happens because write-in poll options or candidates are not visible to other voters. This is not usually an issue in the case of an e-voting system, where new write-in poll options or candidates can be made visible as the election takes place. Alternatively, some locations require write-in candidates or poll options to be registered before the election.
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== Criteria in evaluating voting systems ==
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Various [[:Category:voting system criteria|critera]] are used in evaluating voting systems.  However, it is impossible for one voting system to pass all criteria in common use. For example, [[Arrow's impossibility theorem]] demonstrates that many mutually desirable criteria are mutually inconsistent.
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Voting systems can be abstracted as mathematical functions that select between choices based on the [[utility]] of each option for each voter.  This greatly resembles a [[social welfare function]] as studied in welfare economics and many of the same considerations can be studied. For aspects such as simplicity, dispute, and fraud, the practical implementation is far more important than the abstract function. However, the choice of abstract function puts some constraints on the implementation. For instance, certain voting systems such as First Past the Post, [[Cloneproof Schwartz Sequential Dropping]] (CSSD), or Borda Count can be tallied in one distributed step, others such as IRV require centralization, and others such as multi-round runoff require multiple polling rounds.
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== See also ==
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*[[Table of voting systems by nation]]
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*[[:Category:Voting theory|Voting theory]]
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{{fromwikipedia}}

Revision as of 05:08, 14 February 2005

Voting systems or election methods are methods for groups of people to select one or more options from many, taking into account the individual preferences of the group members. Voting is often seen as the defining feature of democracy, and is best known for its use in elections — but it can also be used to award prizes, to select between different plans of action, or as a means for computer programs to evaluate which solution is best for a complex problem.

A key property of voting systems is that, because they are algorithms, they must be formally defined. Consensus, for example, which is sometimes put forward as a voting system, is more properly a broad way of working with others, analogous to democracy or anarchy.

Aspects of voting systems

The ballot

See: Ballot type

Different voting systems have different forms for allowing the individual to express their tolerances or preferences. In ranked ballot or "preference" voting systems, like Instant-runoff voting, the Borda count, or a Condorcet method, voters order the list of options from most to least preferred. In range voting, voters rate each option separately. In first-past-the-post (also known as plurality voting), voters select only one option, while in approval voting, they can select as many as they want. In voting systems that allow plumping, like cumulative voting, voters may vote for the same candidate multiple times.

District (constituency) size

A voting system may select only one option (usually a candidate, but also an option that represents a decision), in which case it is called a "single winner system", or it may select multiple options, for example candidates to fill an assembly or alternative possible decisions on the measure the ballot posed.

Some countries, like Israel, fill their entire parliament using a single multiple-winner district (constituency), while others, like Ireland or Belgium, break up their national elections into smaller, multiple-winner districts, and yet others, like the United States or the United Kingdom, hold only single-winner elections. Some systems, like the Additional member system, embed smaller districts within larger ones.

Party-list systems

In party-list proportional representation systems, candidates can be aligned with, or nominated by, parties, and the party's list of candidates plays a functional role within the system. These parties may in turn be aligned with other parties, to form coalitions, which can play roles beyond those played by the party. These systems are designed to ensure proportional representation, the idea that the candidates selected from a given party (or, in non-party-list systems, informal grouping) should be in proportion to the votes cast for that party. Some of these systems, however, have election thresholds--minimum numbers of votes cast for a party to win any seats. The purpose of an election threshold is generally to keep very small parties from participating in a parliament, in order to maintain stability of governments.

None of the above option

In some voting systems, voters may choose to select none of the candidates (or poll options), by voting for a "None of the above" option. If this option wins, the election fails, all candidates or poll options are excluded from a subsequent election.

Write-in candidate - poll option

Some elections allow voters to write in the name of a person (or of the poll option) not on the ballot as their candidate (or as a poll option). Write-in candidates (poll options) rarely win and votes are often cast for ineligible people or fictional characters. This happens because write-in poll options or candidates are not visible to other voters. This is not usually an issue in the case of an e-voting system, where new write-in poll options or candidates can be made visible as the election takes place. Alternatively, some locations require write-in candidates or poll options to be registered before the election.

Criteria in evaluating voting systems

Various critera are used in evaluating voting systems. However, it is impossible for one voting system to pass all criteria in common use. For example, Arrow's impossibility theorem demonstrates that many mutually desirable criteria are mutually inconsistent.

Voting systems can be abstracted as mathematical functions that select between choices based on the utility of each option for each voter. This greatly resembles a social welfare function as studied in welfare economics and many of the same considerations can be studied. For aspects such as simplicity, dispute, and fraud, the practical implementation is far more important than the abstract function. However, the choice of abstract function puts some constraints on the implementation. For instance, certain voting systems such as First Past the Post, Cloneproof Schwartz Sequential Dropping (CSSD), or Borda Count can be tallied in one distributed step, others such as IRV require centralization, and others such as multi-round runoff require multiple polling rounds.

See also

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