P3 manipulated — the mild version: three adjacent swaps, no burial, same result¶

Generated from p3_manip_compromise_rr.yaml — do not edit by hand. Regenerate: python STARVote_LH_tabulation_engine/tools_adam/scripts/build_yaml_pages.py.

Method: Ranked Robin (RCV-RR / Copeland) · 1 seat · Expected winner: Dublin

Official tie-break (lot) order: Athens > Bergen > Cork > Dublin > Edinburgh — consulted only if every deterministic tiebreaker stays tied (how the ladder works).

Scenario¶

The manipulation that should worry us more than the book's. The complete reversal is a curiosity — no real voter submits their preferences backwards. But the SAME voter can achieve the SAME outcome with ordinary compromising: submit Dublin>Athens>Bergen>Cork>Edinburgh. That is three adjacent swaps. Nothing is buried, the sincere last choice Edinburgh stays last, and only the compromise candidate Dublin is lifted. Dublin goes 4-0 and wins outright. Exhaustively, 52 of the 119 alternative rankings available to this voter strictly improve their result (44 decided outright or by margin, 8 more only after the lot). Note this is COMPROMISING, not burial — Ranked Robin's documented resistance to burial is untouched and remains true, which makes this worse news rather than better, because compromising is the strategy ordinary voters actually reach for.

Ballots¶

Each row is one voter's ranking, most-preferred first (N: prefix = N identical ballots).

2:Edinburgh>Cork>Athens>Dublin>Bergen
3:Dublin>Edinburgh>Bergen>Cork>Athens
1:Athens>Bergen>Cork>Dublin>Edinburgh
1:Dublin>Athens>Bergen>Cork>Edinburgh

What the engine says¶

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

--- Ranked Robin (RCV-RR / Copeland) Method (single winner) ---
 Tabulating 7 ballots (ranked ballots).

Ballots:
     2 × Edinburgh > Cork > Athens > Dublin > Bergen
     3 × Dublin > Edinburgh > Bergen > Cork > Athens
     1 × Athens > Bergen > Cork > Dublin > Edinburgh
     1 × Dublin > Athens > Bergen > Cork > Edinburgh

Round-Robin — every pair, head-to-head (For – Against):
   Edinburgh  beats Cork        5 – 2
   Edinburgh  beats Athens      5 – 2
   Dublin     beats Edinburgh   5 – 2
   Edinburgh  beats Bergen      5 – 2
   Cork       beats Athens      5 – 2
   Dublin     beats Cork        4 – 3
   Bergen     beats Cork        5 – 2
   Dublin     beats Athens      4 – 3
   Athens     beats Bergen      4 – 3
   Dublin     beats Bergen      6 – 1

--- Pairwise (Round-Robin) Matrix ---
Head-to-head / pairwise comparison — the Ranked Robin tally
Legend: For - Equal Support - Against   (row vs column)
              |  Edinburgh  |   Cork     |  Athens    |  Dublin    |  Bergen    |
---------------------------------------------------------------------------------
  Edinburgh > |     ---     | 5 - 0 - 2  | 5 - 0 - 2  | 2 - 0 - 5  | 5 - 0 - 2  |
       Cork > |  2 - 0 - 5  |    ---     | 5 - 0 - 2  | 3 - 0 - 4  | 2 - 0 - 5  |
     Athens > |  2 - 0 - 5  | 2 - 0 - 5  |    ---     | 3 - 0 - 4  | 4 - 0 - 3  |
     Dublin > |  5 - 0 - 2  | 4 - 0 - 3  | 4 - 0 - 3  |    ---     | 6 - 0 - 1  |
     Bergen > |  2 - 0 - 5  | 5 - 0 - 2  | 3 - 0 - 4  | 1 - 0 - 6  |    ---     |

Win–loss record — Copeland score = wins + ½·ties (highest score wins; ties broken by total margin, then lot order):
    #  Candidate  W–L–T  Copeland  Margin  Beats
    1  Dublin     4–0–0         4     +10  Edinburgh, Cork, Athens, Bergen
    2  Edinburgh  3–1–0         3      +6  Cork, Athens, Bergen
    3  Cork       1–3–0         1      -4  Athens
    4  Athens     1–3–0         1      -6  Bergen
    5  Bergen     1–3–0         1      -6  Cork

Winner — Ranked Robin (RCV-RR): Dublin
   beats every opponent head-to-head — the Condorcet winner.

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

--- 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 5): Dublin
   Outside (4):        Edinburgh, Cork, Athens, Bergen
   One member ⇒ Dublin is the Condorcet winner, beating every rival head-to-head.
   Ranked Robin (RCV-RR) winner Dublin is INSIDE the Smith set. ✓
      Guaranteed: Ranked Robin (Copeland) is Smith-efficient — every member of
      the set outscores every outsider, so the top of the win–loss table is
      always inside the set, however the tie among them is then broken.
   More: 07_Concepts/topics/smith_set.md

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 method_comparisons/manipulability_p3/cases/p3_manip_compromise_rr.yaml

P3 manipulated — the mild version: three adjacent swaps, no burial, same result¶

Scenario¶

Ballots¶

What the engine says¶

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

See also¶