Exercise 6 — Bullet voting backfires: the strategic ballots¶

Generated from ex06_bullet_backfire.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: Cash

▶ Live on BetterVoting: vote · results ↗ (election 7f4f7q · test BV2194).

Scenario¶

The same nine voters as ex06_bullet_honest.yaml, but Ari's four fans now bullet vote — Ari 5, Bree 0, Cash 0 — hoping to drag Ari past the compromise candidate. It works halfway: Bree crashes from 25 points to 13 and out of the runoff, and Ari (20) becomes a finalist. But the runoff Ari inherits is against Cash (21) — and Ari loses it 5-4, because zeroing Bree never manufactured any Ari-over-Cash preferences. The bullet voters demoted their sure second choice and elected their nightmare. STAR's runoff is exactly the feature that makes this gamble costly. Exercise: ex06_bullet_backfire.md. Ballots and cast are this repo's own. Live on BetterVoting (Test ID BV2194): https://bettervoting.com/7f4f7q/results — with RCV-IRV and Ranked Robin races: on the bullet ballots all three methods elect Cash.

Ballots¶

The ballots as marked — the filled bubble is the score given, and the score is the number in its column:

#	Ari	Bree	Cash
1	5	0	0
2	5	0	0
3	5	0	0
4	5	0	0
5	0	2	5
6	0	2	5
7	0	2	5
8	0	2	5
9	0	5	1

The same ballots as the file records them:

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

Ari,Bree,Cash
5,0,0 # Ari fan 1 of 4 — BULLET: Bree zeroed (honest was 5,3,0)
5,0,0 # Ari fan 2 of 4 — BULLET: Bree zeroed
5,0,0 # Ari fan 3 of 4 — BULLET: Bree zeroed
5,0,0 # Ari fan 4 of 4 — BULLET: Bree zeroed
0,2,5 # Cash fan 1 of 4 — unchanged
0,2,5 # Cash fan 2 of 4 — unchanged
0,2,5 # Cash fan 3 of 4 — unchanged
0,2,5 # Cash fan 4 of 4 — unchanged
0,5,1 # The lone Bree fan — unchanged, and she decides the runoff

What the engine says¶

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

[Divergence from STAR]
  STAR                   = Cash
  Choose-One (Plurality) = Ari   (differs from STAR)
  Approval               = Ari   (differs from STAR)

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

[STAR Voting]
 Tabulating 9 ballots.
Count × Ari,Bree,Cash
    4 ×   5,   0,   0
    4 ×   0,   2,   5
    1 ×   0,   5,   1

[STAR Voting: Scoring Round]
 The two highest-scoring candidates advance to the next round.
   Cash          -- 21 -- First place
   Ari           -- 20 -- Second place
   Bree          -- 13
 Cash and Ari advance.

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

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

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
               |   * Ari    |    Bree   |  * Cash   |
-----------------------------------------------------
       * Ari > |    ---     |4 - 0 - 5  |4 - 0 - 5  |
        Bree > | 5 - 0 - 4  |   ---     |1 - 4 - 4  |
      * Cash > | 5 - 0 - 4  |4 - 4 - 1  |   ---     |

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

[Condorcet Loser]
  Condorcet Loser: Ari — loses every head-to-head matchup — elected by Choose-One (Plurality), Approval!

[Score Distribution] (how many ballots gave each star rating)
                Score
Candidate  5  4  3  2  1  0  | Total   Avg
Ari        4  0  0  0  0  5  |    20   2.2
Bree       1  0  0  4  0  4  |    13   1.4
Cash       4  0  0  0  1  4  |    21   2.3

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/ex06_bullet_backfire.yaml

Exercise 6 — Bullet voting backfires: the strategic ballots¶

Scenario¶

Ballots¶

What the engine says¶

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

See also¶