Split Cycle vs. Schulze — a spoiler nobody voted for¶
The tabulatable evidence behind Split Cycle — the method that hands the tie back, claim-checked. Holliday & Pacuit (arXiv:2004.02350; Public Choice 197, 2023) claim that among clone-independent methods only Split Cycle is immune to spoilers, and that Schulze is not. This is that claim, run.
| Case (source) | Ballots | What it shows |
|---|---|---|
page · split_cycle_schulze_spoiler_c5_b40.yaml |
40 | Cascade beats Bryce 40–0 — not one voter prefers Bryce. Bryce wins nothing, ever. Yet Schulze elects Cascade without her on the ballot and Everglade with her on it. Split Cycle keeps Cascade in both fields. |
Reproduced independently (this is not the paper's own profile — it's the smallest one a pref_voting search turned up), and LH-only: neither the LH engine nor BetterVoting implements Schulze or Split Cycle, and LH's Copeland result here is a tie.
Running it¶
uv run STARVote_LH_tabulation_engine/tools_adam/pref_voting_tabulation_engine/cycle_resolution_report.py method_comparisons/split_cycle/cases/split_cycle_schulze_spoiler_c5_b40.yaml
uv run STARVote_LH_tabulation_engine/tools_adam/pref_voting_tabulation_engine/cycle_resolution_report.py method_comparisons/split_cycle/cases/split_cycle_schulze_spoiler_c5_b40.yaml --drop Bryce
| Copeland (Ranked Robin) | Minimax | Ranked Pairs | Schulze | Split Cycle | |
|---|---|---|---|---|---|
| Without Bryce | Arches, Cascade, Denali | Everglade | Cascade | Cascade | Cascade |
| With Bryce | Cascade, Denali | Everglade | Cascade | Everglade | Cascade, Everglade |
Read it fairly — the lesson page states the limits, and they're real: this needs a five-candidate election with no Condorcet winner and a Smith set of everyone; Ranked Pairs isn't convicted by this particular profile; Split Cycle's escape is to return two winners, which a public election would then have to break somehow; and the criterion is narrower than IIA — it wouldn't flag this library's own STAR spoiler case. Nothing here is evidence about STAR or Ranked Robin.
Concept pages: Split Cycle, claim-checked · cycle resolution · Condorcet reading list · up: method_comparisons