Exercise 14 — The transfer machine: a book club buys two novels (STV)¶

Generated from ex14_two_novels.yaml — do not edit by hand. Regenerate: python STARVote_LH_tabulation_engine/tools_adam/scripts/build_yaml_pages.py.

Method: STV (proportional, ranked ballots) · 2 seats · Expected winners: Austen, Camus

▶ Live on BetterVoting: vote · results ↗ (election tk776t · test BV2201).

Scenario¶

A nine-member book club buys TWO novels by ranked ballot, counted with STV (the proportional cousin of RCV-IRV). Round 1: Austen has 5 first choices — over quota — and is elected; her surplus transfers, as fractions of the five ballots that elected her, to their next choice, Bronte. From there STV fills the second seat the way it always does — moving surpluses, and eliminating from the bottom if nobody is over the line — and Camus takes it. Seats: Austen + Camus. The drill follows one ballot through the whole journey — how much of it elected Austen, and where the remainder came to rest — to see how STV keeps a vote moving until it lands. How large that surplus is, and whether any elimination is needed, depends on which of the two published Droop quotas the count applies; the report below names the one it uses, and part (f) of the exercise works these same ballots both ways. Exercise: ex14_transfer_machine.md. Ballots and cast (novelists as candidates) are this repo's own. Live on BetterVoting (Test ID BV2201): https://bettervoting.com/tk776t — the vote page works, but BV's STV tabulator currently returns a server error on /results for this election, and for its fully-ranked probe twin BV2202 (bj8dfc, ex14_two_novels_fullranks.yaml) — a live BV bug, since DIAGNOSED: the count ends with Camus reaching quota as the sole remaining hopeful, and BV's IRV.ts redistributes his surplus over an empty candidate list ([].reduce with no initial value throws). Full bisection (BV2203-2205) and ready-to-file issue: 06_Other/STV/bv_stv_sole_survivor_crash/. The seats above are the LH engine's; BV STV races whose endgame leaves a hopeful standing (ywckmg, kcf8vf, 39py93) compute fine.

Ballots¶

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

5:Austen>Bronte>Camus>Dickens
1:Bronte>Camus
3:Camus>Dickens

What the engine says¶

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

--- STV / Single Transferable Vote (multi-winner — 2 seats) ---
  Exercise 14 — The transfer machine: a book club buys two novels (STV)
 Tabulating 9 ballots (ranked ballots).
 2 seats; quota = 3.00 (exact Droop, votes/(seats+1)) — 33.3% of 9.
 Elected at >= quota, and every surplus is measured from it.
 (Hand-count Droop, floor(9/3)+1 = 4, is a different but equally standard rule.)

ROUND 1
Candidate      Votes  Status
-----------  -------  --------
Austen             5  Elected
Camus              3  Hopeful
Bronte             1  Hopeful
Dickens            0  Hopeful

FINAL RESULT
Candidate      Votes  Status
-----------  -------  --------
Austen          3.00  Elected
Camus           3.00  Elected
Bronte          3.00  Rejected
Dickens         0.00  Rejected


Winner(s) — STV / Single Transferable Vote (multi-winner — 2 seats)
  Austen
  Camus

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 4): Austen
   Outside (3):        Bronte, Camus, Dickens
   One member ⇒ Austen is the Condorcet winner, beating every rival head-to-head.
   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 01_STAR/05_Practice/cases/ex14_two_novels.yaml

Exercise 14 — The transfer machine: a book club buys two novels (STV)¶

Scenario¶

Ballots¶

What the engine says¶

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

See also¶