# [EM] So I got an email... / Binomial STV

Richard Lung voting at ukscientists.com
Mon Apr 11 12:53:17 PDT 2022

```Thank you, Kevin,

I would not expect to see exactly the same result with Binomial STV as
traditional STV, especially in the single member case. This is because
single memer preference voting, in all its variations, does not have a
rational count, but only a less accurate ordinal count of more or less.
BSTV uses keep value ratios, for both an election count and an exclusion
count (of preferences in reverse). In the case of (multi-member) STV
there is a rational election count but not a rational exclusion count,
so there is less dearth of preference information, there, but still a
dearth, compared to BSTV.

The difference this makes to the voters (for whom the systenm is for) is
that they are informed:   Vote for the candidates, in order of greatest
choice. Vote also for the candidates in reverse order of least choice.
Your last preference (according to the number of candidates) counts as
much against a candidate as your first preference counts toward a candidate.

In short, the more preferential information obtained gives voters more
power of choice.

In test elections, I would look for the onset of an entropy effect: In
Irish STV elections, the use of preferences rapidly falls off. This
might be less marked with BSTV because of the power to express dislikes,
as well as likes. The comparison I am thinking of is the arrow of time
(pun not intended). Laws of physics make time reversible. Just as BSTV
makes preferences reversible. But times arrow prevails, and this is
accounted for by entropy. Some BSTV elections might not have this
"entropic" effect, so it  might be necessary to use significance tests
of how far candidates are from a quota, without solely relying on an
over-all BSTV result based on a geometric mean candidate keep values of
the election count and the exclusion count.

Regards,

Richard Lung.

On 10/04/2022 23:03, Kevin Venzke wrote:
>   Hi Richard,
>
> Le dimanche 10 avril 2022, 03:21:38 UTC−5, Richard Lung <voting at ukscientists.com> a écrit :
>> As recently written in my Winners or representation thread, I don't think the
>> failure to achieve a Condorcet winner, as in Burlington justifies calling the
>> preference voting system used, a mistake. It is an adverse consideration but not
>> a definitive mistake. And as a 1 in 135 occurence, it is not highly significant
>> -- not significant enough, in my opinion, to justify over-loading RCV with a CW
>> veto on the result. I might compare it to leaving the scaffold on a building as
>> a permanent feature.
> This is a reasonable stance, but the "1 in 135" argument can be questioned given
> that every RCV election is conducted under RCV's specific voting and nomination
> incentives. That is, we can't be sure that the candidate selection would be the
> same between different methods, or that voters would vote the same way after
> accounting for strategic incentives.
>
> Compare the argument that every known FPTP election also elects the Condorcet
> winner, as far as anyone can really tell.
>
>> RCV could be improved. -- I invented such a system, Binomial STV that works in
>> single districts as well as multi-member districts (tho single districts do not
>> work nearly as well as  [STV] multi-member districts). However I would not dream
>> of employing an improved system (BinomialSTV) without test elections, which I
>> would naturally like it to receive, before official employment.
> You recently shared how to solve Binomial STV ("BSTV") for the three-candidate
> one-winner case. Based on winner agreement rates, BSTV seems to be about as
> different from RCV as possible. I wouldn't say all methods sit squarely between
> them, but it's almost true that RCV and BSTV are closer to any other method than
> each other.
>
> This makes it hard for me to imagine what properties there could really be in
> common between these two methods.
>
> So I wonder, if you were to have the opportunity to conduct test elections for
> Binomial STV, what standards would you use to assess whether the tests were
> successful?
>
> Kevin
```