Approval voting is a single-winner electoral system in which voters mark all the candidates they support, instead of just choosing one. The candidate with the highest approval rating is elected. Approval voting is currently in use for government elections in St. Louis, Missouri and Fargo, North Dakota.
Score voting, sometimes called range voting, is an electoral system for single-seat elections. Voters give each candidate a numerical score, and the candidate with the highest average score is elected. Score voting includes the well-known approval voting, but also lets voters give partial (in-between) approval ratings to candidates.
A Condorcet method is an election method that elects the candidate who wins a majority of the vote in every head-to-head election against each of the other candidates, whenever there is such a candidate. A candidate with this property, the pairwise champion or beats-all winner, is formally called the Condorcet winner or Pairwise Majority Rule Winner (PMRW). The head-to-head elections need not be done separately; a voter's choice within any given pair can be determined from the ranking.
Disapproval voting is any electoral system that allows many voters to express formal disapproval simultaneously, in a system where they all share some power. Unlike most electoral systems, it requires that only negative measures or choices be presented to the voter or representative. If used to select candidates for an office, or for continuation to a next round of voting or play, it is either single- or multi-winner, as everyone who is not disapproved of is in effect a winner, for that round.
A protest vote is a vote cast in an election to demonstrate dissatisfaction with the choice of candidates or the current political system. Protest voting takes a variety of forms and reflects numerous voter motivations, including political apathy. Where voting is compulsory, casting a blank vote is available for those who do not wish to choose a candidate, or to protest. Unlike abstention elsewhere, blank votes are counted.
"None of the above" (NOTA), or none for short, also known as "against all" or a "scratch" vote, is a ballot option in some jurisdictions or organizations, designed to allow the voter to indicate disapproval of the candidates in a voting system. It is based on the principle that consent requires the ability to withhold consent in an election, just as they can by voting "No" on ballot questions. It must be contrasted with "abstention", in which a voter does not cast a ballot.
The majority favorite criterion is a voting system criterion that says that, if a candidate would win more than half the vote in a first-preference plurality election, that candidate should win. Equivalently, if only one candidate is ranked first by a over 50% of voters, that candidate must win. It is occasionally referred to simply as the "majority criterion", but this term is more often used to refer to Condorcet's majority-rule principle.
In single-winner voting system theory, the Condorcet loser criterion (CLC) is a measure for differentiating voting systems. It implies the majority loser criterion but does not imply the Condorcet winner criterion.
Majority judgment (MJ) is a single-winner voting system proposed in 2010 by Michel Balinski and Rida Laraki. It is a kind of highest median rule, a cardinal voting system that elects the candidate with the highest median rating.
Rated, evaluative, graded, or cardinalvotingsystems are a class of voting methods which allow voters to state how strongly they support a candidate, which involves giving each one a grade on a separate scale. Cardinal methods and ordinal methods are the two categories of modern voting systems.
Ranked voting is any voting system that uses voters' orderings (rankings) of candidates to choose a single winner or multiple winners. More formally, a ranked rule is one that depends only on which of two candidates is preferred by a voter, and as such does not incorporate any information about intensity of preferences. Ranked voting systems vary dramatically in how preferences are tabulated and counted, which gives them very different properties.
Satisfaction approval voting (SAV), also known as equal and even cumulative voting, is an electoral system that is a form of multiwinner approval voting as well as a form of cumulative voting. In the academic literature, the rule was studied by Steven Brams and Marc Kilgour in 2010. In this system, voters may approve a number of candidates, and each approved candidate receives an equal fraction of the vote. For example, if a voter approves 4 candidates, then each candidate receives a 0.25 fractional vote. The election winners are those candidates that receive the highest fractional vote count.
Proportional approval voting (PAV) is a proportional electoral system for multiwinner elections. It is a multiwinner approval method that extends the highest averages method of apportionment commonly used to calculate apportionments for party-list proportional representation. However, PAV allows voters to support only the candidates they approve of, rather than being forced to approve or reject all candidates on a given party list.
Sequential proportional approval voting (SPAV) or reweighted approval voting (RAV) is an electoral system that extends the concept of approval voting to a multiple winner election. It is a simplified version of proportional approval voting. It is a special case of Thiele's voting rules, proposed by Danish statistician Thorvald N. Thiele in the early 1900s. It was used in Sweden from 1909-1921, when it was replaced by a cruder "party-list" style system as it was easier to calculate, and is still used for some local elections.
An approval ballot, also called an unordered ballot, is a ballot in which a voter may vote for any number of candidates simultaneously, rather than for just one candidate. Candidates that are selected in a voter's ballot are said to be approved by the voter; the other candidates are said to be disapproved or rejected. Approval ballots do not let the voters specify a preference-order among the candidates they approve; hence the name unordered. This is in contrast to ranked ballots, which are ordered. There are several electoral systems that use approval balloting; they differ in the way in which the election outcome is determined:
A major branch of social choice theory is devoted to the comparison of electoral systems, otherwise known as social choice functions. Viewed from the perspective of political science, electoral systems are rules for conducting elections and determining winners from the ballots cast. From the perspective of economics, mathematics, and philosophy, a social choice function is a mathematical function that determines how a society should make choices, given a collection of individual preferences.
Combinatorial participatory budgeting, also called indivisible participatory budgeting or budgeted social choice, is a problem in social choice. There are several candidate projects, each of which has a fixed costs. There is a fixed budget, that cannot cover all these projects. Each voter has different preferences regarding these projects. The goal is to find a budget-allocation - a subset of the projects, with total cost at most the budget, that will be funded. Combinatorial participatory budgeting is the most common form of participatory budgeting.
The sincere favorite or no favorite-betrayal criterion is a property of some voting systems, that says voters should have no incentive to vote for someone else over their favorite. It protects voters from having to engage in lesser-evil voting or a strategy called "decapitation".
The highest median voting rules are a class of graded voting rules where the candidate with the highest median rating is elected.
In political science and social choice theory, the spatialmodel of voting is a mathematical model of voting behavior. It describes voters and candidates as varying along one or more axes, where each axis represents an attribute of the candidate that voters care about. Voters are modeled as having an ideal point in this space, and preferring candidates closer to this point over those who are further away; these kinds of preferences are called single-peaked.
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