Instant-Runoff Voting (IRV)

For reference, this is what many people assume when they see “Preferential Ballot,” but it is NOT what Condorcet/Ranked-Pairs is about.

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© James Hamblin, YoutTube
  1. One voting round: The voter marks the candidates on a single ballot in the order of his or her preference.
  2. First counting round: All the ballots are counted, considering their first-preference candidates; if this results in a candidate receiving a majority of ballots, then that candidate is elected, and we’re done; otherwise
  3. Subsequent counting rounds: We eliminate the candidate having the lowest number of ballots, reallocating these ballots in terms of their next-preference choices … until a majority candidate is determined.

Issues

Two CandidatesThree or more Candidates
  • Works well.
  • Chooses the candidate who is preferred by the majority.
  • Voters’ full preferences do not come into play. Lesser preferences have no effect until all higher-preference candidates on a given ballot have been eliminated, and then only if that candidate is not already eliminated. (See Why not IRV/AV?”)
  • Sensitive to the order of elimination, which can affect which other candidates are eliminated.
  • Spoiler Effect: A candidate can still lose due to similarity of other candidates, though the effect is not as severe as with FPTP.
  • Chooses a winner on a better majority basis than FPTP, but a most-preferred candidate can still be eliminated, not elected, and it’s possible, in fact, that the least-preferred candidate is elected, not eliminated.  This is NOT a Condorcet method.
  • Candidates/parties must appeal-to and be accountable beyond their first-preference supporters.

This system is indeed an improvement over plurality/first-past-the-post: it is easy to understand, and only slightly more complex to do, but we can easily do significantly better with Condorcet/Ranked-Pairs, as proposed here. If this is the most we can achieve, however, it’s still a worthwhile improvement over plurality/first-past-the-post.

Ranked-Pairs and other Condorcet methods do NOT operate by “eliminating” candidates – all ballot preferences for all valid ballots come into play in determining the outcome.

Next: Mixed-Member PR Voting

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