Independence of Irrelevant Ballots

IIB is equivalent to the Blank Ballot Criterion. It says that a voter who has no preference between any candidates should not impact which of them wins or loses by voting.

A generalization of this concept is to treat an irrelevant ballot as simply being a ballot with no preference between the candidates in a set of candidates, and the requirement as being that that ballot shouldn't impact who wins or loses among that set of candidates.

In general, Largest remainder methods violate this criterion because an irrelevant voter will change the size of the quota. See the Quota rule#Notes for an example.

Blank Ballot Criterion

Definitions

A blank ballot is a ballot that fails to indicate any preference between any of the candidates.

Statement of Criterion

The addition of one or more blank ballots cannot change the winner.

Complying Methods

• Complies: Approval voting, Cardinal Ratings, Schulze
• Fails: Median Ratings