Voting system

Voting systems are methods (algorithms) for choosing between different options. They are most commonly used in elections, but are also used for many other purposes: to award prizes, to select between different plans of action, or even by computer programs to evaluate which solution is best for a complex problem.

Criteria in evaluating voting systems

Various criteria are used in evaluating voting systems. However, it is impossible for one voting system pass all criteria in common use. For example, Arrow's impossibility theorem demonstrates that the following criteria are mutually contradictory:

• The voting system should always give a result
• If a voter improves the ranking of a particular option, that option should not be disadvantaged (monotonicity criterion)
• Removing a candidate should not change the winner of an election unless that candidate is the winner (independence of irrelevant alternatives)
• Every possible outcome should be achievable
• Non-dictatorship (i.e. more than one person's vote matters)

Other criteria which have been used to judge voting systems include:

• Proportionality
• Simplicity - speed
• Level of strategy
• Reduction of potential for dispute after the fact

Another dilemma in voting systems is whether the system should choose a candidate is intensely popular among most people and intensely unpopular among the rest over a candidate universally but unenthusiastically accepted. This is the tolerances versus preferences problem, and it occurs in economics as well, e.g. in study of monopoly.

List of Systems

Single Winner Systems

• Approval voting
• Borda count
• Condorcet's method
• Coombs' method
• Copeland's method
• First-past-the-post (also called Plurality)
• Preferential or Instant Runoff Voting (also called Alternative Vote)
• Range voting
• Runoff voting

Multiple Winner Systems (not party-list)

• Approval voting
• Block voting
• Borda count
• Cumulative voting
• Single non-transferable vote
• Single transferable vote

Allocation methods for Party-list proportional representation

• d'Hondt method
• least remainders method[?]
• Sainte-Laguë method[?]

Disapproval

In all of these systems, there is a choice about whether to include an option to vote against filling the seat. This is sometimes implemented by erecting a threshold which winning candidates must pass, other times by entering a theoretical "None of the above" candidate into the running.

The public dis/approval of specific ballot measures is called a referendum. Disapproval of a specific candidate in office is representative recall. It is noteworthy that both are means of publicly limiting and directing the powers of public officials or parties, but this aspect of disapproval voting isn't well studied. In the study of consensus decision making, the "blocking" of measures or nominations is a significant concern, and this literature may be of interest to anyone seriously studying disapproval of one or all of the choices.

Famous Theoreticians of Voting Systems

• Kenneth Arrow
• Jean-Charles de Borda
• Andrew Inglis Clark
• Marquis de Condorcet
• Charles Lutwidge Dodgson
• Maurice Duverger
• Thomas Hare
• William H. Riker

See also: political scientists

External Links

• http://www.fairvote.org (Center for Voting and Democracy)
• ODP Category on Voting Systems (http://dmoz.org/Society/Politics/Campaigns_and_Elections/Voting_Systems/)

See also

• Consensus
• Democracy
• Duverger's law
• electoral reform
• Grassroots democracy
• Politics
• Representative democracy
• Spoiler effect
• Table of voting systems by nation
• Tactical voting
• Two-party system