Glossary

amendment procedure

A voting procedure that pairs a proposal under consideration with the status quo. If a variation on the proposal is introduced it is paired with the proposal and voted on as an amendment prior to the final vote. If the amendment succeeds, then the amended proposal is eventually paired with the status quo in the final vote.

approval voting

A voting procedure in which voters may vote for (approve of) as many of the alternatives as they wish.

Borda count

A voting procedure in which each voter forms a preference ranking for all alternatives. Given n alternatives, each voter casts n votes for his or her most preferred alternative, n-1 votes for his or her second most preferred alternative, etc. The alternative that receives the most votes wins.

cardinal utility

A preference expressed in terms of intensity on a finite scale.

Condorcet criterion

Holds for a voting system if it selects the Condorcet winner whenever one exists.

Condorcet efficiency

Percentage of elections in which the Condorcet winner is selected (assuming there is a Condorcet winner).

Condorcet winner

An alternative that beats or ties all others in a series of pairwise contests.

consistency

Holds for a voting system if when the electorate is divided arbitrarily into two parts and separate elections in each part result in the same alternative being selected, an election of the entire electorate also selects that alternative.

coordinated macromanipulation

Manipulation by coalitions.

cumulative vote

A semiproportional voting system in which each voter is alloted a number of votes equal to the number of candidates to be elected. The voters may give one vote each to that number of candidates or accumulate their votes, allocating two or more to one candidate.

declared-strategy voting

(DSV) A novel group decision-making procedure in which preference is specified using voting strategies.

deterministic

Holds for a voting system if it always produces an election winner.

effectiveness

The power of a ballot to influence the election outcome.

expressiveness

The extent to which a voting system allows voters to voice their honest opinions without sacrificing the power of their votes.

independence from irrelevant alternatives

Holds for a voting system if it always produces the same results given the same profile of ordinal preferences.

insincere vote

A vote that is not sincere.

limited vote

A semiproportional representation system similar to plurality voting, except voters are limited to casting a number of votes that is less than the number of candidates to be elected.

list proportional representation

(list PR) A proportional representation system in which political parties prepare lists that include as many candidates as there are seats to be filled. The voters select the list for the party they support and deposit it in their ballot envelopes. After the votes are counted and the seats are allocated, each party selects from the top of its list the number of candidates corresponding to the number of seats won. Some variations on this procedure allow voters the option of crossing out candidates or selecting particular candidates from a party list.

majoritarian voting method

A voting method that selects a winner based on pairwise comparisons between alternatives.

majority rule

A voting system in which the alternative receiving more than half the votes wins.

manipulability

Holds for a voting system in which voters may sometimes obtain a more preferred outcome by casting ballots not reflective of their true preferences.

micromanipulation

Manipulation by individuals.

monotonicity

Holds for a voting system if when a voter raises the valuation for a winning alternative it remains a winning alternative, and when a voter lowers the valuation for a losing alternative it remains a losing alternative.

multi-stage voting method

A voting procedure that uses either different choice functions at different stages of the procedure, or one choice function iteratively on diminishing sets of alternatives.

neutrality

Holds for a voting system if the system does not favor any alternative.

non-dictatorial

Holds for a voting system if the election outcome is not determined entirely by a single individual.

NP-hard

Cannot be solved in polynomial time.

ordinal utility

A preference expressed in terms of relative position in a list of alternatives ordered according to preference.

Pareto optimality

Holds for a voting system if when every voter prefers alternative x to alternative y, alternative y is not selected.

pivot probability

The probability that a voter will be decisive in creating or breaking a first-place tie between two candidates (or for elections that select M alternatives, the probability that the voter will be decisive in creating or breaking an -place tie).

plurality voting

A voting procedure in which each voter votes for his or her single most preferred alternative (or when n alternatives are to be selected, voters vote for their n most preferred alternatives). The alternative that receives the most votes wins.

positional voting method

A voting method that selects a winner based on information about individuals' preference orderings.

proportional representation system

(PR) A voting system that promotes close correspondence between the proportion of supporters of each party (or other interest group) in the electorate and the proportion of seats held by each party in a governing body.

rational

Holds for voters that take actions they believe are most likely to lead their preferred outcome -- regardless of whether it is reasonable for them to prefer that outcome.

runoff election procedure

A two-stage voting procedure in which the alternatives are first considered together, and then if no alternative receives the majority of votes, a majority rule election is held between the two alternatives receiving the largest numbers of votes.

semiproportional voting system

A voting system with similar properties as the proportional voting systems, but resulting in somewhat less proportional representation.

sincere vote

A vote such that for any two alternatives under consideration, the voter has given greater or equal weight to the more preferred of those alternatives.

single-stage voting method

A voting method that selects a winner in a single round of vote tabulation.

single non-transferable vote

(SNTV) A special case of the limited vote in which voters may specify only a single candidate on their ballots, regardless of how many seats are to be filled.

single transferable vote

(STV) A voting procedure in which voters submit a preference raking over all the candidates. Any candidate that receives more than a certain number of first-place votes is elected. If the elected candidates receive more votes than necessary for election, their excess votes are distributed to the other candidates in accordance with the second-choice preferences of the voters. Once again, any candidate that receives more than a certain number of votes is elected and the redistribution procedure continues. If the redistribution procedures reaches a point where there are no more votes to be redistributed and there are still more elected positions to be filled, the candidate with the least votes is eliminated and the votes for that candidate are redistributed.

sophisticated vote

A vote determined to be optimal through game theoretic analysis, which takes into account the likely strategies of the other voters; a type of strategic vote.

stability

Producing the same outcome from a given set of ballots each time it is counted.

strategic vote

A vote such that for any two alternatives under consideration, the voter has given greater or equal weight to the more preferred of those alternatives.

utilitarian voting method

A voting method that requires voters to assign utility values to each alternative. These utilities are aggregated to determine the election outcome.

utility

A preference; a measure of personal value or satisfaction.

voting strategy

A plan made prior to an election that prescribes the course of action a voter should take given any contingency that can arise.