|
|
Voting system(Redirected from Voting systems)
Voting systems are methods (algorithms) 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 (See consensus decision making for disciplined consensus methods and how they relate to voting). Additionally to the basic process of voting in local districts, the forming of a government forms the basics of a democracy.
Aspects of voting systemsThe ballotDifferent 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) sizeA 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 the Republic of 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 systemsIn 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 optionIn 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; typically it will be re-run with a new set of candidates or poll options, all previous ones (having lost to "none of the above") being excluded. The philosophy behind having a "None of the above" option is that all possible alternatives should be considered in a decision; this option represents all of the alternatives not considered explicitly. Write-in candidate - poll optionSome 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 systemsVarious criteria are used in evaluating voting systems. These criteria define potentially desirable properties of voting systems mathematically, so that different systems can be compared using the same criteria. It is impossible for one voting system to pass all criteria in common use. For example, Arrow's impossibility theorem demonstrates that several desirable features of voting systems are mutually contradictory. For this reason, someone implementing a voting system has to decide which criteria are important for the election. These criteria include:
Voting systems are also judged with less-mathematical criteria:
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, or Borda count can be tallied in one distributed step, others such as Instant-Runoff require centralization, and others such as multi-round runoff require multiple polling rounds. List of systemsSingle-winner systemsSingle-winner systems can be classified by ballot type:
They can also be classified on how many times votes can be counted. Methods like Plurality, Borda, and Approval with single counting rounds are simpler since voters can be sure to know how their votes will be applied. Binary voting methods
Ranked voting methods
Rated voting methods
Multiple-winner systems
Related terminology
Famous theoreticians of voting systems
See also
External links
|
|
The contents of this article are licensed from Wikipedia.org under the GNU Free Documentation License. How to see transparent copy
|
BiologyDaily.com 2005. Legal info Privacy |