Exercise 5 — The squeezed bridge-builder (IRV vs STAR)¶

Generated from ex05_center_squeeze.yaml — do not edit by hand. Regenerate: python STARVote_LH_tabulation_engine/tools_adam/scripts/build_yaml_pages.py.

Method: STAR (single winner) · 1 seat · Expected winner: Brook

▶ Live on BetterVoting: vote · results ↗ (election 6bry7c · test BV2192).

Scenario¶

A club presidency with two wings and one bridge-builder. Brook is scored 3+ by every single voter and beats each rival head-to-head (5-4 over Avi, 6-3 over Cole) — the Condorcet winner. But Brook has only 2 first choices, so RCV-IRV eliminates Brook FIRST and elects the wing candidate Avi 5-4: the center squeeze. STAR reads the full scores instead: Brook tops the scoring round 31-23-18 and wins the runoff against Avi 5-4. A drill for the squeeze mechanism (see the center-squeeze topic pages); ballots and cast are this repo's own. Exercise: ex05_center_squeeze.md. Live on BetterVoting (Test ID BV2192): https://bettervoting.com/6bry7c/results — three races on the same opinions: STAR (Brook), RCV-IRV (Avi — the squeeze, live), Ranked Robin (Brook).

Ballots¶

Row 1 = candidate names; each later row is one voter's 0–5 scores (a N × prefix = N identical ballots).

Avi,Brook,Cole
5,3,0 # 4 voters: Avi's wing — Brook acceptable, Cole never
5,3,0
5,3,0
5,3,0
0,3,5 # 3 voters: Cole's wing — Brook acceptable, Avi never
0,3,5
0,3,5
3,5,0 # 1 voter: Brook first, leans Avi
0,5,3 # 1 voter: Brook first, leans Cole

What the engine says¶

The count, step by step — the rounds and how the winner is reached:

[Divergence from STAR]
  STAR                   = Brook
  Choose-One (Plurality) = Avi   (differs from STAR)
  RCV-IRV                = Avi   (differs from STAR)
  Note: no ballots had tied scores, so RCV-IRV vs STAR here is a genuine
        method difference, not a tie-breaking artifact.
  Note: Ranked Robin (RCV-RR) agrees with STAR, so RCV-IRV is the lone
        outlier — the classic center-squeeze signature.
  Full round-by-round reports (generated for review):
  RCV-IRV rounds: cases_tabulated/ex05_center_squeeze_RCV-IRV_tabulated.txt

--- STAR Voting Method (single winner) ---

[STAR Voting]
 Tabulating 9 ballots.
Count × Avi,Brook,Cole
    4 ×   5,    3,   0
    3 ×   0,    3,   5
    1 ×   3,    5,   0
    1 ×   0,    5,   3

[STAR Voting: Scoring Round]
 The two highest-scoring candidates advance to the next round.
   Brook         -- 31 -- First place
   Avi           -- 23 -- Second place
   Cole          -- 18
 Brook and Avi advance.

[STAR Voting: Automatic Runoff Round]
 The candidate preferred in the most head-to-head matchups wins.
   Brook         -- 5 -- First place
   Avi           -- 4
   Equal Support -- 0
 Brook wins.
   Runoff math:
     9  ballots cast
   − 0  Equal Support (no preference between the two finalists)
     ─
     9  voters with a preference  (majority = 5)
           Brook 5 (56%)  ·  Avi 4 (44%)

[STAR Voting: Winner — STAR Voting Method (single winner)]
 Brook

Full audit — preference matrix, Condorcet, and score distribution¶

--- Runoff (Preference) Matrix ---
Head-to-head / pairwise comparison
Legend: For - Equal Support - Against
        * indicates Top 2 Finalist
               |   * Avi    | * Brook   |    Cole   |
-----------------------------------------------------
       * Avi > |    ---     |4 - 0 - 5  |5 - 0 - 4  |
     * Brook > | 5 - 0 - 4  |   ---     |6 - 0 - 3  |
        Cole > | 4 - 0 - 5  |3 - 0 - 6  |   ---     |

[Condorcet Winner]
  Condorcet Winner: Brook — matches the STAR winner

[Condorcet Loser]
  Condorcet Loser: Cole — loses every head-to-head matchup

[Score Distribution] (how many ballots gave each star rating)
                Score
Candidate  5  4  3  2  1  0  | Total   Avg
Avi        4  0  1  0  0  4  |    23   2.6
Brook      2  0  7  0  0  0  |    31   3.4
Cole       3  0  1  0  0  5  |    18   2.0

Everything in one file: the _tabulated mirror (regenerated on every run; every analysis forced on).

Run it yourself:

python STARVote_LH_tabulation_engine/starvote_larry_hastings.py 01_STAR/05_Practice/cases/ex05_center_squeeze.yaml

Exercise 5 — The squeezed bridge-builder (IRV vs STAR)¶

Scenario¶

Ballots¶

What the engine says¶

Full audit — preference matrix, Condorcet, and score distribution¶

See also¶