[EM] Plurality Loser Elimination And Trunk Yanking Proposals

[Forest Simmons]

If we emphasize least ranking rather than most truncation, we can call the
method "Ranking Yanking" :-)

El mar., 24 de ago. de 2021 12:08 p. m., Forest Simmons <
forest.simmons21 at gmail.com> escribió:

> While there is no pairwise winner among the remaining alternatives ...
> eliminate from among said remaining alternatives the alternative X with the
> fewest (transferred) votes along with all of the alternatives beaten
> pairwise by X
> EndWhile.
>
> Then elect the pairwise winner among the remaining alternatives (possibly
> the only remaining alternative).
> EndProcedure
>
> The idea is that if the Plurality Loser is a weak alternative deserving
> removal, then so are the alternatives beaten by it pairwise (if any).
>
> In this context "eliminate" means remove from the ballots and transfer the
> Plurality votes to the top remaining alternative on each ballot.
>
> It turns out that this method always elects from a subset of Smith called
> Banks.
>
> Note that the procedure becomes IRV by removal of the phrase, "along with
> all of the alternatives beaten pairwise by X".
>
> If that phrase is too big of a price to pay for Condorcet compliance, then
> there is no hope for tweaking IRV into a decent proposal.
>
> In that case, better to replace Plurality Loser with Implicit Approval
> Loser, and get a monotonic Banks method:
>
> While there is no pairwise winner among the remaining alternatives ...
> eliminate from among the remaining alternatives the alternative X ranked on
> the fewest ballots along with all of the alternatives beaten pairwise by X
> EndWhile.
>
> Then elect the pairwise winner among the remaining alternatives (possibly
> the only remaining alternative).
> EndProcedure
>
> You may recognize this method as a reformulation of TACC (Total Approval
> Chain Climbing) with "total approval" replaced by "implicit approval".
>
> Note that "ranked on the fewest" is the same as "truncated on the most" so
> the method could be called "Truncation Yanking," since the most truncated
> alternative yanks the alternatives it beats pairwise.
>
> As I mentioned, Truncation Yanking (TY) is monotone (unlike any IRV tweak)
> and it is much simpler to tally than any IRV tweak.
>
> Also, since true clones do not straddle truncation boundaries, the method
> is clone independent.
>
> Anybody know of another simple Banks compliant method with these nice
> properties?
>
> Forest
>
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