====================================================================== SOURCE FILE: coombs_ex20_district2.yaml TABULATED FILE: coombs_ex20_district2_tabulated.txt ====================================================================== election_title: "Coombs Ex.20 — District II: 7 voters, B wins outright" scenario_description: |- District II of Felsenthal's Coombs reinforcement example. Source: Dan S. Felsenthal (2010), Appendix A7, Example 20. Seven voters, three candidates: 1×(A>B>C), 6×(B>A>C). B is ranked first by 6 of 7 — an absolute majority on the first count — so Coombs elects B immediately and never reaches its deletion step. No paradox here; this is the second clean district whose combination with the first produces one. The source prints this district as "6 voters" while listing 7, and its amalgamated table sums to 41, which only works with 7. We take the tables as authoritative and flag the typo rather than quietly choosing. District I (coombs_ex20_district1.yaml) also elects B. Together they elect A (coombs_ex20_amalgamated.yaml) — the reinforcement paradox. Labels are Felsenthal's own A/B/C so the case can be read side by side with the paper's table. Tabulated as RCV-IRV, the mirror-image count Coombs inverts; with a first-round majority both methods elect B by the same step. For the Coombs count run tools_adam/pref_voting_tabulation_engine/coombs_report.py. paradoxes: [multiple-districts] voting_method: RCV_IRV num_winners: 1 ballots: |- 1:A>B>C 6:B>A>C expected_winners: - B # file: coombs_ex20_district2.yaml ====================================================================== TABULATION RESULTS ====================================================================== --- RCV / Instant-Runoff Voting (single winner) --- Coombs Ex.20 — District II: 7 voters, B wins outright Tabulating 7 ballots (ranked ballots). FINAL RESULT Candidate Votes Status ----------- ------- -------- B 6 Elected A 1 Rejected C 0 Rejected Winner(s) — RCV / Instant-Runoff Voting (single winner) B --- Smith Set (the generalized Condorcet winner) --- The smallest group whose every member beats every candidate outside it — the honest answer to "who is even in contention?". Smith set (1 of 3): B Outside (2): A, C One member ⇒ B is the Condorcet winner, beating every rival head-to-head. RCV-IRV winner B is INSIDE the Smith set. ✓ Not guaranteed — RCV-IRV is not Smith-efficient — but it holds here. More: 07_Concepts/topics/smith_set.md