[EM] STV - the transferrable part is OK (fair), the sequential round elimination is not

[Raph Frank]

On Mon, Nov 2, 2009 at 8:38 PM, Juho <juho4880 at yahoo.co.uk> wrote:
> On Nov 2, 2009, at 1:53 PM, Raph Frank wrote:
>> Districts with 7+ seats seem reasonable, and give reasonable
>> proportionality.
>
> I guess there is some practical limit to how may candidates the voters are
> willing to evaluate and rank. Districts of 7+ already offer reasonable
> proportionality (approximate quite well the x% of votes => x% of seats
> principle). Also the number of candidates should be small enough in this
> case so that the voters need not rank too many candidates (e.g. 10
> candidates from each party).

Well, even with a larger number of seats, a voter would waste very
little of their vote, even if they only voted for 2-3 candidates.

Assuming you only ranked 3 candidates and they all get elected with
double the quota, only 12.5% of your vote would be exhausted.

In practice it is rare that candidates get much more than 10% above
the quota (except the candidates who are elected on the first count).

A reasonable rule would be to keep ranking until you hit a candidate
who has a reasonable chance of being elected, but isn't so popular
that he will gain much more than a quota in the first round.

> Also the number of districts has an impact here. If there are e.g. 10
> districts of size 7 there could be a party with 10% support and no seats
> although from a nation wide perspective 10% of the votes would justify 7
> seats.

True, however that assumes that the party has very constituent support.

If it varies a little from region to region, then maybe they would win
a few seats at least.

The could also decide to focus their resources from the whole country
on the 7 regions that they are most likely to win a seat in.  (though
that might get a backlash due to using "outsiders").

> Yes, districts with independent elections set similar limitations in all
> systems. In list based systems it is just somewhat easier to extend them
> e.g. so that proportionality will be counted at country level. Candidate
> lists could still be regional if one so wants (the summed up votes would
> determine proportions at the country level, and seats could then be
> propagated back down (as in the Finnish proposal)).

You could also pretend that there is just 1 national constituency and
voters just happened to only vote for local candidates.

Also, you could list local candidates on the ballot, but give a
write-in slot.  The write in could allow voters to vote for a
candidate from other regions.

This reduces the complexity of the ballot for locals, but also allows
voters to vote for a write in candidate if they wish.

> Yes, this is one way to extend STV to offer better proportionality at the
> country level. This method seems to combine some list type features with STV
> voting.
>
> (Btw, did you consider the possibility of parties running their most popular
> candidates (that will be elected in any case) outside the party list. Is
> that a valid strategy in this method?)

It depends on what you mean here.

It doesn't suffer from the same problem as MMP, where you can gain
extra votes by using a decoy list.  Only votes which would otherwise
be exhausted are transferred to the national level.

A voter who votes for an independent doesn't also get to cast a party
vote, so you can't have your supporters support a fake independent
locally while still voting for the party with their party vote.

However, the method would still have the standard issues with vote
management.  This is pretty much inherent to PR-STV.  If party
supporters vote for the weaker party candidates instead of a very
popular candidate, then when the popular candidate is elected, fewer
of the party supporters' votes are used up.