[EM] IRV and PR-STV Re: examination of plaintiff's memorandum re IRV in Minneapolis

[Raph Frank]

On Tue, Nov 11, 2008 at 2:18 PM, Abd ul-Rahman Lomax
<abd at lomaxdesign.com> wrote:
> At 10:45 AM 11/10/2008, Raph Frank wrote:
>>
>> On Mon, Nov 10, 2008 at 3:32 AM, Abd ul-Rahman Lomax
>> <abd at lomaxdesign.com> wrote:
>> > Is this complicated? Yes. Is it fair? Well, up to the election of the
>> > last
>> > candidate, yes, it is clearly fair. With the last candidate, the
>> > election
>> > effectively becomes the same as an instant runoff voting election, with
>> > the
>> > problems associated with that.
>>
>> I don't see why the last seat being filled is that much different from
>> the others.  The negative effects are always there, though because
>> factions aren't quite solid coalitions in practice, PR-STV doesn't
>> display the effects quite so much (maybe).
>
> Okay, sometimes it isn't the last seat. Rather than saying "last seat," I
> should say, "up until the point where non-election eliminations begin."

I wouldn't consider when a candidate is elected an elimination.

I assume that you mean "until a round where the lowest candidate is eliminated?"

> Raph's approach, by the way, shows the weakness of study through constructed
> examples. As he notes, "because factions aren't quite solid coalitions in
> practice," which is like saying "because people aren't quite like
> stereotypical caricatures of the party of the candidate they choose in a
> single election to vote for," what is usually missing from examples is any
> consideration of how realistic the example is.

Right.  However, examples like this clearly show a given effect.

If there was some random inter-faction preferences, then it would make
it harder to illustrate.

It is a balance between clarity and realism.

Also, another benefit of PR-STV over IRV is that the C faction can
pick which of the A and B factions actually get elected.  Ofc, if they
hold a primary before the election and only run 1 candidate, then this
effect is lost.  However, this incentive is reduced if they think they
might get more than 1 seat.

> There is only one way to study election method performance, with any hope of
> objectivity,, and that is utility analysis, the approach of Warren Smith.
> The same kind of mistake could be made there: an artificial utility profile
> might warp the results, but some of the simulations he's done do attempt to
> generate, at the outset, reasonable utility profiles, perhaps using issue
> distance in n-space.

Ofc, Warren is still looking into make it work for multi-member elections.

> [The A faction winner would] probably [be] A1,
> *though we cannot tell without understanding the
> preference strengths*.)

However, A1 isn't the condorcet winner.  An approval internal vote
would pick A2.

Ofc, in the near term, the primary would likely be plurality, so A1 would win.

>> PR-STV will run as follows
>>
>> Quote = 35 (approx)
>
> The Droop Quota is 34.

Yeah, I know, but the extra vote makes little difference (and I did
say 'approx')

> STV's problem is the same as that of IRV, it is in the candidate
> eliminations. Any candidate elected before eliminations begin is clearly
> legitimate. (This is *certain* if the Hare quota is being used, and quite
> reasonable under the Droop quota.)

Correct, and this is why CPO-STV is superior as it doesn't do any eliminations.

> If the A1 and A3 voters "retaliate" by truncating, themselves, not a
> problem. A1, A2, and A3, all members of the same faction, negotiate, on
> behalf of their supporters, who is to win the faction's votes and thus a
> seat, and, benefit that comes with it, they get to use up their last
> remaining unassigned votes. In Asset systems I'd propose, they might choose
> A4!, someone eligible but not on the ballot.

So, PR-STV with Asset backup.  All unused voting power could go to the
first choice on the ballot.