[EM] PRfavoringracialminorities

[Raph Frank]

On 8/25/08, Kristofer Munsterhjelm <km-elmet at broadpark.no> wrote:
>  The divisor method choice differs not just when you're by the threshold,
> but also at the "discontinuity points" of their respective rounding. Also, I
> think that if you're going to use a divisor method, there's no point in not
> using Webster instead of D'Hondt or Adams -- that is, unless you think the
> large/small party bias is desirable.

Right, I was thinking more about fairness.  If all parties are
expected to get 2+ seats, then there isn't that much of a difference
between the two.

However, for the initial distribution, I think d'Hondt is better as it
rounds downwards, this forces parties to get 2 full seats before being
considered.

This would be more important if the threshold was 1 seat though (as
Webster's would allow parties with 0.5 seats worth of votes to get a
seat, and that is potentially open to abuse).

Websters is fairer as it has much less of a bias between large and
small parties.  There were posts on this list comparing bias in
Webster's and d'Hondt.  The conclusion was very slight bias for
Websters and much larger bias for d'Hondt.

My view would be that as long as all the parties are expected to get a
reasonable number of seats, the Webster's is better.  If there is a
possibility of single seat parties, then d'Hondt is better.

This is what modified Sainte-Lague tries to achieve with its larger
first divisor.  Ofc, that means voting for a small party can be
throwing your vote away.

>  If you want even less bias, you could use Warren's adjusted divisor method,
> since in party list PR,

Is that modified Sainte-Lague?

>  Or, for that matter, if it's 4% and you want to show that the party has
> support. Electoral support numbers can encourage parties by themselves, I
> think - for parties on their own, or for coalitions. If the method has at
> least some strategy, and we know that no method is absolutely free of
> strategy, then knowing that there's support for a party may make others who
> think that "it only has 3% support, voting for it is definitely a waste"
> reconsider when they see that it really has 4.9%.

Another option would be to have 2 votes, one is a 'vote of support'
and the other is your real vote.

However, that is probably better implemented using a ranked party
system, even if only allowing 2 ranks.

>  Part of what I'm trying to achieve when considering MMP methods based on
> PR-STV (not necessarily STV though) is of making the resulting method immune
> from negative campaigns on the basis that the PR-STV base produces an
> effective threshold that's higher than what was the case for the party list
> method, and so one should return to party list.

Have you read about Fair Majority Voting?
http://www.mathaware.org/mam/08/EliminateGerrymandering.pdf

This is similar to MMP, but it doesn't assign any extra seats.  What
happens is that each party gets a multiplier.  This multiplier is
multiplied by the number of votes each party member receives and the
candidate with the highest total wins each constituency.

The multipliers are selected so that each party receives the correct
number of seats nationwide.

If a party gets to many seats, it would receive a low multiplier and
thus would lose a few marginal seats to a party which has to few.

The paper shows that under reasonable conditions, there is also a
solution and it is unique.

I am not sure if it could be applied to multiseat constituencies.
PR-STV would be especially hard as a central office wouldn't be able
to work out who would win as it tries new multipliers.  Also, the
non-monotonic nature of PR-STV could play havoc with the algorithm
even if the central station could recalculate the results on the fly.
Increasing a party's multiplier could result in it getting fewer
seats.

Also, it still has the problem dealing with independent candidates and
also, assumes that parties are primary over voting for individual
candidates.

I still think that PR-STV with the ability to transfer exhausted
ballots to the national count is the best way to go.  This means that
each vote (or fraction of a vote) is either used to elect a local
candidate or to elect a national candidate.  By making the quota the
same in both cases, the count is completely fair.  It also allows
voters who just want to vote party list to do so and ones who want to
rank all their local candidates to do so and both methods give an
equal ratio of representation to vote.

>  20: Left > Center > Right
>  20: Right > Center > Left
>   1: Center > Left = Right
>
>  and a fair scoring function, you'd probably get a center party that (since
> it's the CW) gets somewhat more power than either Left and Right, with the
> Left and Right parties being of equal power and taking the remainder. For
> the case I've given, this may cause a problem with Center being a kingmaker,
> but I think that's more a problem with the assumption that power is directly
> proportional to the number of seats, than with the election method in
> general.

Have you considered PR-STV with Condorcet loser elimination.  Rather
than eliminating the weakest candidate, the condorcet loser is
eliminated.

This has the effect of discriminating against candidates who are not
near the centre.  Also, the condorcet winner is immune from
elimination.

Another option is to directly centre bias the election method.

For example, you could have 5 seater constituencies, and give the
condorcet winner a 'free' seat and then use the ballots to elect 4
using PR-STV.

This would give a centerist party a disproportionally large seat total.

Also, the PR-STV stage would encourage honest voting of the rankings.

If the constituency was split 51 to 49 between 2 parties, then each
party would get 2 seats in the PR-STV stage.  The condorcet seat would
then tip the balance 3-2 in favour of the majority party.

>  If you have PR-STV, you can just "emulate" party list by altering a vote
> for a single party to a vote for the entire list, in the order the list has
> been set up (for closed list) or in the order the voter specified (for open
> list).

True, that is probably easier than trying to make it complex.

>  But that only works for systems in the spirit of divisor methods. For
> instance, for the Condorcet election above, Center is ranked above Left and
> Right in the social order, but I think that the correct assembly of two is
> one of Left and one of Right. Still, it's a step towards understanding
> multiwinner methods.

Well, with a 2 seat assembly, the Droop PR rule says that any faction
with more than 1/3 of the votes must be a seat.  I think this is
almost the definition of a PR method.  If a PR method doesn't meet
that criteria, then it is only semi-PR at best.