Condorcet ranking

A Condorcet ranking is an ordering of candidates such that:

• The Condorcet winner, if one exists, is ranked first.
• The secondary Condorcet winner (the new Condorcet winner if the Condorcet winner is eliminated), if one exists, is ranked second.
• The tertiary Condorcet winner (the new Condorcet winner if the Condorcet winner and the secondary Condorcet winner are eliminated), if one exists, is ranked third.
• etc.

and

• The Condorcet loser, if one exists, is ranked last.
• The secondary Condorcet loser (the new Condorcet loser if the Condorcet loser is eliminated), if one exists, is ranked next-to-last.
• The tertiary Condorcet loser (the new Condorcet loser if the Condorcet loser and secondary Condorcet loser are eliminated), if one exists, is ranked third-to-last.
• etc.

Smith set ranking

A Smith ranking (Smith set ranking) is the same as a Condorcet ranking, except instead of being defined in terms of the Condorcet winner and Condorcet loser, it is defined in terms of the Smith set and Smith loser set, and when there is a multi-member Smith set, the candidates in the Smith set may be ranked in any order so long as they are all ranked above non-Smith set candidates, with the same applying for the Smith loser set candidates with regards to being ranked lower than non-Smith loser set candidates. When there is a Condorcet ranking (one doesn't always exist), the Smith ranking will be the same as the Condorcet ranking. There will always be at least one Smith ranking, and it is possible to have more than one (each of which will differ only on the order in which Smith or Smith loser candidates are ranked).

The generalized Smith ranking is a Smith ranking where all candidates in the Smith set are equally ranked and the same holds for the Smith loser set; for example:

2 A

2 B

1 C

The generalized Smith ranking is A=B>C, meaning A and B are tied for 1st place, and C is in 2nd place. Note that any of A>B=C, B>A=C, or A=B>C would be valid Smith rankings, but only the third is a generalized Smith ranking; this is because the generalized Smith ranking assumes neutrality as to who is superior within the Smith and Smith loser sets. This may make it an appropriate tool to demonstrate how various groups of candidates would compare across all Smith-efficient methods. There will always be one and only one generalized Smith set ranking.

Note that a variant of generalized Smith rankings can be created to address the unanimity/Pareto criterion. For example:

34 A>B>C>D

33 B>C>D>A

33 C>D>A>B

A pairwise beats B pairwise beats C pairwise beats D pairwise beats A, so all candidates here are in the Smith set. However, C is unanimously preferred to D, so the Pareto-satisfying generalized Smith ranking would be A=B=C>D, whereas the regular generalized Smith ranking would be A=B=C=D.

Notes

Methods that produce Condorcet rankings include Kemeny-Young and Ranked Pairs; methods that produce Smith rankings include Pairwise Sorted Methods.