[EM] Simple Acceptable Ranked Choice Voting

[Forest Simmons]

Very Good!

I have another more elaborate application of max gradient in mind, but I
was hoping that some choice of seed would be good enough for a simple
stand-alone max gradient.

Too bad Brenham's Gross Loser Elimination is not monotone.






On Fri, Jan 13, 2023, 5:39 AM Kevin Venzke <stepjak at yahoo.fr> wrote:

> Hi Forest,
>
> Let's tackle this question first:
>
> > Also how does DSC do with regard to Chicken Defense?
>
> I'm glad you asked. DSC is a ""great"" CD method, maybe the only one.
>
> I have complained before that the CD criterion allows the larger faction
> in a fragmented
> majority to truncate without issue. That seems like a problem both
> philosophically (i.e.,
> what is the significance of faction size in a chicken game?) and also
> practically (i.e. a
> faction might truncate out of an erroneous belief that their faction is
> the large one).
>
> Consider this election:
>
> 40 A
> 35 B
> 25 C>B
>
> IRV and Condorcet methods go soft and let B win. Maybe B was driving a
> truck and C was
> driving a car. But with DSC justice is blind. It stands its ground and
> elects A, handing
> the fragmented majority a well-earned punishment!
>
> And it goes much further:
>
> 100 A>B
> 99 B
> 98 C>B
> 97 D>B
> ... etc
> 50 Z>B
>
> DSC will still elect A.
>
> > I wonder how this DSC-with-max-gradient-finisher would do:
> >
> > Initialize X as the DSC winner. Then ...
>
> I tried this with a few methods (DSC, DAC, FPP, approval) as I felt unsure
> you really meant
> to pick DSC for this. However, I seem to find that generally, no matter
> the seed method,
> this approach is violating monotonicity. Maybe this is creating ways to
> rig the initial
> chain head.
>
> > While X is covered, replace X with the candidate X' with the strongest
> defeat against X
> > among those candidates that cover X.
> >
> > Elect the last value of X... i.e. the first X that turns out to be
> uncovered.
> >
> > Does any of the DSC burial resistance flavor make it through this
> afterburner?
>
> DSC isn't particularly burial-resistant. Its significance is in lacking
> truncation
> incentive. But since it likes to agree with FPP, that might moderate the
> burial issue.
>
> As far as simulations:
>
> Seeding with FPP or DSC made it a lot worse with minimal defense, so I
> can't say I like
> those ones.
>
> Some best-to-worst rankings for each seed type, and also C//A, with four
> candidates:
>
> Compromise:
> DAC > Approval > C//A > Gross score > DSC > FPP
>
> Truncation:
> FPP > DSC > DAC > Gross score > Approval > C//A
>
> Burial:
> C//A > FPP > Approval > DAC > DSC > Gross score
>
> For burial, FPP is the best seed probably because you can't manipulate the
> initial chain
> head through adjusting your lower preferences.
>
> In general it seems like the covering rule will introduce burial, because
> it gives voters
> some levers to indirectly attack a potential chain head.
>
> Kevin
> votingmethods.net
>
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