Re: [PLUG] Excellent talk on preferential voting at PLUG North Tue 12/11...

[brainbuz via plug <plug@lists.phillylinux.org>]

I'm really glad that people enjoyed the talk and are talking about it.

The slides are up on https://techinfo.brainbuz.org

For the record STV (Single Transferable Vote) refers to multi-member 
methods that use preferential ballots and try to equalize the impact 
that each ballot has on the final result.

My main thrust for current development on Vote::Count is implementation 
of Multi-Member methods, and I may offer a follow up talk on them.

STV sets a threshold based on the number of ballots and then elects the 
highest choice that is above the threshold and then determines a surplus 
that is available for transfer. There are a lot of different sub methods 
for STV.

On 2019-12-11 11:02, Fred Stluka via plug wrote:
> PLUG folks,
>
> John Karr gave an excellent talk on "preferential voting" at PLUG
> North Tue 12/11.
>
> I had heard of "Single Transferable Vote" aka "Ranked Choice Voting",
> and had concluded that it was a pretty good idea.  I had written this
> short summary of it:
> - http://bristle.com/Vote/#single_transferable_vote
>
> After hearing John's talk and chatting with a few very knowledgeable
> attendees like Rich Freeman and John Ashmead (and others whose
> names I didn't catch), I now know a lot more detail.
>
> As I now understand it...
>
> There are 2 basic forms of ballots for preferential voting:
> - "Rank" (aka "Ordinal") - Voter picks 1st, 2nd, 3rd choice, etc.
> - "Range" (aka "Cardinal" - Voter assigns preference score from
>    a specified range like 1-5.  May give any score to each
>    candidate, including multiple with the same score.  Not giving
>    a score is the same as giving score 0.
>
> There are several different ways to count the votes.  Mostly, they
> say that a "Majority Winner" wins, if there is one.  For example, a
> candidate who gets more than 50% of the 1st choice votes when a
> a Rank ballot is used.  They differ mostly in how to proceed when
> there is no such clear winner.
>
> The simplest (and the only one I'd ever heard of before) is "Instant
> Runoff Voting" (IRV).  If no candidate has more than 50% of the
> 1st choice votes, you drop the candidate with the fewest 1st
> choice votes, convert the 2nd choice on those ballots to 1st
> choice, and re-count.  If still no winner, drop the candidate with
> the next fewest 1st choice votes, etc., until you have a winner.
>
> This generally works MUCH better than our current system of
> voting ("Plurality" winner) because it solves the "Spoiler" problem
> (aka "Favorite Betrayal").  That is, voters can safely vote for a
> long-shot 3rd-party candidate without risk of "throwing away"
> their vote.  They're not missing out on the chance to vote for
> their preference among the 2 major parties, to prevent the
> strongly undesired other major party candidate from winning.
>
> However, in certain cases, especially when a long-shot candidate
> is not such a long-shot and actually has a real chance to beat
> one of the major party candidates, it can still go wrong.  Rich
> Freeman explained this very well before the talk started.  Here's
> a short video that explains it like he did:
> - "Favorite Betrayal in Plurality and Instant Runoff Voting"
>     https://www.youtube.com/watch?v=JtKAScORevQ
>
> Since IRV is not perfect, there are various other techniques that
> can be used to count the ballots, discard weaker candidates, and
> choose a single winner.  Unfortunately, none of them is perfect.
> There are pros/cons to each of them.  But they pretty much ALL
> work better than our current "Plurality" system.
>
> John Karr discussed various criteria for evaluating such techniques
> (Complexity, Consistency, Later Harm, etc.) and various techniques
> (Condorcet, Smith Set, Borda, etc.).  He also showed some sample
> data sets and how the different techniques chose different winners.
> He used the open source Vote::count software that he's written in
> Perl in his demos.
>
> Be sure to catch his talk if he gives it again at another PLUG
> location.  Was the talk video taped?  If so, someone please post
> the video.  Also, are the slides available on-line?
>
> Thanks for an excellent talk, John!
> --Fred
> ------------------------------------------------------------------------
> Fred Stluka -- Bristle Software, Inc. -- http://bristle.com
> #DontBeATrump -- Make America Honorable Again!
> ------------------------------------------------------------------------
>
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