Criteria of voting systems

At the time of the choice of a Voting system, it is important to determine the advantages and the disadvantages of this system. This is why were developed criteria of voting systems . No voting system can fill totality of these criteria. The Theorem of impossibility of Arrow, for example, affirms that it is not possible to find a voting system satisfying the first five criteria quoted here. It is thus at the organization organizing the elections to determine which are the criteria which the voting system must absolutely respect and which are those which can be put aside.

Criteria of Arrow

Criterion of totality

All the possible proposals must be likely to be adopted.

Criterion of universality

The procedure must give a result on the whole of the configurations: one must always be able to deduce a collective will starting from the individual wills.

Criterion of unanimity

If a candidate is preferred by the totality of the voters, it must be gaining it.

Criterion of independence

The introduction of an additional candidate should not modify the existing relative order between the other candidates in each bulletin.

Criterion of not-dictatorship

The preferences of an individual alone should not determine the collective choice.

Criterion of Condorcet

In bulletins with classification of the candidates, if there exists a gaining of Condorcet, i.e. a candidate which, confronted with any other candidate, is always gaining it then this candidate must be elected.

Respects this criterion: the Method Black, the method of elimination of Bordered, the method of Dodgson, the method of Kemeny-Young, the method Nanson, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the sum of the defeats.
does not respect this criterion: the Méthode Bordered, the method Bucklin, the Méthode of Coombs, the alternative Vote.

Criterion of the loser of Condorcet

In bulletins with classification of the candidates, if there exists losing of Condorcet, i.e. a candidate which confronted with any other candidate is always losing then this candidate should not be elected.

Respects this criterion: the Méthode Bordered, the Méthode Black, the method of elimination of Bordered, the Méthode of Coombs, the alternative vote, the method of Kemeny-Young, the method Nanson, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the method of the min-max of Smith.
does not respect this criterion: the Bucklin method, method of Dodgson, method of the min-max, the sum of the defeats.

Criterion of consistency

If the bulletins are divided in two groups and if a candidate is gaining it in each group, it must be gaining it of the elections.

Respects this criterion: the Vote by approval, the Méthode Bordered, the Vote balanced.
does not respect this criterion: the Method Black, the method of elimination of Bordered, the method Bucklin, the Méthode of Coombs, the method of Dodgson, the method of Kemeny-Young, the alternative Vote, the method of Kemeny-Young, the method of the min-max, the method Nanson, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the method of the min-max of Smith, the sum of the defeats.

Criterion of the clones

a whole of clones is a whole of candidates (at least two) such as any other candidate is located, or before all the clones, or after all the clones. A whole of clones cannot contain all the candidates .

Criterion of the clones : so in a whole of clones, one eliminates a candidate, if the old one gaining were in this whole of clones, the new one gaining must remain there and if the old one gaining were not in the whole of clones, it must remain gaining it.

Respects this criterion: the Vote by approval, the Vote balanced, the alternative Vote, method of elimination per pair, the Condorcet Method with arrangement of the pairs per decreasing order, the Method Schulze.
does not respect this criterion: the Method Black, the Méthode Bordered, the method of elimination of Bordered, the method Bucklin, the Méthode of Coombs, the method of Dodgson, the method of Kemeny-Young, the method of the min-max, the method Nanson, the method of the min-max of Smith, the sum of the defeats.

Criteria of independence

total

If, in an election where X is gaining, one adds a new candidate Y, the new one gaining can be only X or Y.

local

or indifference with the least relevant English options (: Irrelevant room alternate independence from).

the whole of Smith is the smallest whole of candidates who gain against all the candidates out of the unit.

Criterion of local independence : gaining does not change if one adds a candidate who is not in the whole of Smith.

Respects this criterion: method of Kemeny-Young, method of elimination per pair, the Condorcet Method with arrangement of the pairs per decreasing order, the Method Schulze, method of the min-max of Smith.
does not respect this criterion: the Method Black, the Méthode Bordered, the method of elimination of Bordered, the method Bucklin, the method of Coombs, the method of Dodgson, the alternative vote, the method of the min-max, the method Nanson, the sum of the defeats.

Criterion of participation

If X is gaining and that one adds bulletins in which X is placed always better than Y, Y should not be the new winner.

Criterion of the majority

If a candidate is placed first in more half of the bulletins, it must be elected.

Respects this criterion: the Method Black, the method of elimination of Bordered, the Méthode of Coombs, the method of Dodgson, the alternative Vote, the method of Kemeny-Young, the method Nanson, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the method of the min-max of Smith, the sum of the defeats.
does not respect this criterion: the Méthode Bordered.

Criterion of monotony

If a candidate is not gaining and if one retrogresses it in certain bulletins without then modifying the relative order of the other candidates it does not have to be able to gain.

Respects this criterion: the Vote by approval, the Vote balanced, the Method Black, the Méthode Bordered, the method Bucklin, the method of Kemeny-Young, the method of the min-max, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the method of the min-max of Smith, the sum of the defeats.
does not respect this criterion: the method of elimination of Bordered, the Méthode of Coombs, the method of Dodgson, the alternative Vote, the method of the min-max, the method Nanson, the method of elimination per pair.

Criterion of mutual majority

If there exists a whole of candidates who are placed before the others in more half of the bulletins, gaining it must belong to this unit.

Respects this criterion: the method of elimination of Bordered, the method Bucklin, the Méthode of Coombs, the alternative Vote, the method of Kemeny-Young, the method Nanson, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the method of the min-max of Smith.
does not respect this criterion: the Method Black, the Méthode Bordered, the method of Dodgson, the method of the min-max, the sum of the defeats.

Criterion of Paréto

If candidate X is placed, in all the bulletins, behind the candidate Y then it cannot gain.

Respects this criterion: the Méthode Bordered, the method Black, the method Bucklin, the method of elimination of Bordered, the Méthode of Coombs, the method of Dodgson, the method of Kemeny-Young, the alternative Vote, the method Nanson, the method of the min-max, the method of the min-max of Smith, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the sum of the defeats, the Vote by approval, the Vote balanced.
does not respect this criterion:

Criterion of symmetry per inversion

If a candidate is gaining and if one arranges, in each bulletin, the candidates in the inverse order, this same candidate must lose.

Respects this criterion: the Vote by approval, the Vote balanced, the Method Black, the Méthode Bordered, the method of Kemeny-Young, the method Nanson, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze.
does not respect this criterion: the method of elimination of Bordered, the method Bucklin, the Méthode of Coombs, the method of Dodgson, the alternative Vote, the method of the min-max, the method of elimination per pair, the method of the min-max of Smith, the sum of the defeats.

Criterion preferably secret

If a candidate gains and that one preferably modifies the orders in the bulletins behind the gaining candidate, this one must remain gaining.

Respects this criterion: the alternative Vote.
does not respect this criterion: the Method Black, the Méthode Bordered, the method of elimination of Bordered, the method Bucklin, the Méthode of Coombs, the method of Dodgson, the method of Kemeny-Young, the method of the min-max, the method Nanson, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the method of the min-max of Smith, the sum of the defeats.

Criterion of Smith

the whole of Smith is the smallest whole of candidates who gain against all the candidates out of the unit Criterion of Smith : Gaining must belong to the whole of Smith.

Respects this criterion: the method of elimination of Bordered, the method of Kemeny-Young, the method Nanson, the method of elimination per pair, the Méthode Condorcet with arrangement of the pairs per decreasing order, the Méthode Schulze, the method of the min-max of Smith.
does not respect this criterion: the Method Black, the Méthode Bordered, the method Bucklin, the Méthode of Coombs, the method of Dodgson, the alternative vote, the method of the min-max, the sum of the defeats.

Criterion of Schwartz

the whole of Schwartz is in the following way made up

a group of head is a group of candidates who did not lose any confrontation with candidates who are not in the group of head .
a minimal group of head is a group of head which does not contain a smaller group of head .
the whole of Schwartz consists of all the candidates belonging to at least a minimal group of head .

Criterion of Schwartz : Gaining must belong to the whole of Schwartz.

Criteria of invulnerability to the tactical votes

Criterion of not-compromising

A voter should not be able to place a candidate at the top of a candidate whom he actually prefers.

Criterion of not-burial

A voter should not be able to bury a candidate whom it would have normally placed in median position.

Criterion of not-overvaluation

A voter should not be able to overestimate a candidate so as to reserve for his candidate preferred a duel easy to overcome.

See too

Internal bond

Sources

This article contains portions of text resulting from the article in English: Criteria de Black Cretney

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