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BV2133 — Pet poll II: four methods, four winners

The sequel to BV2132, tuned harder: add a fourth pet and every method elects a different one. The sharpest possible "the method chooses the winner" demonstration — 32 voters, one ballot set, four winners.

▶ Live on BetterVoting: vote · results ↗ (election dyxrbr, Test ID BV2133).

Frozen export: bv2133_dyxrbr_pet_poll_four_winners_bv_export.json.

The electorate

Four pets (Dog, Cat, Fish, Bird), 32 voters in four blocs:

 9 voters:  Bird > Cat > Fish > Dog       scores  Dog0 Cat2 Fish1 Bird4
10 voters:  Fish > Cat > Bird > Dog       scores  Dog2 Cat4 Fish5 Bird3
 7 voters:  Dog  > Cat > Fish > Bird      scores  Dog3 Cat2 Fish1 Bird0   (mild Dog fans)
 6 voters:  Dog  > Cat > Fish > Bird      scores  Dog5 Cat2 Fish1 Bird0   (die-hard Dog fans)

Four methods, four winners

Race Winner Our engine BetterVoting Why Read · run
Plurality Dog Dog Dog most first choices (13) — but 19 rank Dog last page · .yaml
RCV-IRV Fish Fish Fish Bird then Cat eliminated; transfers pile on Fish (19–13) page · .yaml
Approval Bird Bird Bird widely approved (19) at the 3+ threshold page · .yaml
STAR Cat Cat Cat score leaders Cat (84) & Fish (72) advance; Cat wins runoff 22–10 page · .yaml

Every race is cross-checked LH engine = BetterVoting. Four methods, four different pets — nobody wins twice.

Why every method picks someone else

  • Plurality → Dog. Dog owns the biggest first-choice bloc (13) from two tiers of Dog fans, so choose-one crowns it — despite 19 of 32 voters ranking Dog dead last.
  • RCV-IRV → Fish. Dog can't grow (everyone else ranks it last). Bird (9) is eliminated first, lifting Cat; then Cat is squeezed out and its transfers land on Fish, which passes Dog 19–13.
  • Approval → Bird. At a "3-or-more = approve" bar, Bird collects the 9 Bird-firsts plus the 10 Fish-firsts (who also approve Bird) = 19 — more than anyone. Broad acceptability, not first-place passion.
  • STAR → Cat. Cat is nobody's favorite but everyone's solid second — top score total (84), and it wins the head-to-head runoff against Fish 22–10. The consensus candidate.

Provenance

Created via create_bv_test_election.py as one multi-race BV election (dyxrbr) with made-up ballots tuned for a four-way split. BetterVoting's four race results match our engines exactly.

The pets set

See also