[EM] Free riding

[Raph Frank]

On 9/4/08, Kristofer Munsterhjelm <km-elmet at broadpark.no> wrote:
>  Not necessarily PAV, but a method that's based on Approval and would
> otherwise be as good as STV, if such a beast exists. What kind of strategy
> can be used in PAV?

If a candidate is certain to win, then there is no point in voting for him.

PAV becomes party list PR if everyone approves the candidates from
their party and doesn't approve anyone else.

It also has the same strategic problem that voters who vote for a
party which doesn't win don't get any representation and can't
transfer their vote.

Since PAV is likely to be used in multiseat districts (rather than
nationwide like party list PR).  This is potentially a bigger problem
as the threshold is much higher.

It could also require voting pacts for smaller parties to get
representation.  This effectively strips voters of the ability to pick
who they vote for, if they want to support that party.

Also, if d'Hondt is used, it favours large parties/coalitions in general.

In the case of a coalition, agreeing the number of candidates each
member party would run is critical.  Parties wouldn't be allow run
more than the agreed number of candidates (or at least there would
have to be some way for voters to distinguish between coalition
candidates and party candidates).

Perhaps, the coalition would create a 'party' label for the coalition.
 All members of the coalition would advise their supporters to approve
all members of the coalition.  Ofc, this leads to an incentive to
defect.

>  Allowing voters to pick the candidate to vote for would be very tedious;
> the algorithm would have to run 200 rounds of voting.

It would be automatic based on their ratings.

> If this was a
> single-winner method, you could have used a cardinal ratings (range)
> equivalent of approval strategy A, but I'm not sure how you'd make a
> multiwinner version of that.

Not sure, for multi-winner, there needs to be some kind of mechanism
for deciding who has already obtained representation.

Perhaps, the approval winner is selected, and everyone who voted for
them has their vote decreased as a proportion of how many votes they
voted for that candidate.

This is basically RRV, but when the vote is split over multiple rounds.

>  More generally, this could be considered DSV. Within the category of DSV,
> one cuold probably make a method that vote-manages on behalf of all voters
> more effectively than any party can.

Yeah.

> Parties that run vote-management can't gain more
> seats than they have, proportionally, unless they run some candidates as
> independents. However, to do so would look somewhat dirty and the party
> might lose genuine personal votes as a consequence.

This means that parties are considered primary.  Ofc, if you want to
have a mix of personal and party based votes, vote management might be
unavoidable.

>  To make that method work, you'd have to have a way of counting party
> support, when examining preference orderings, so you know how many seats the
> parties are entitled to. First preference wouldn't work. You could have a
> "you have two votes" ballot, but that could be gamed.

Maybe the voter would indicate if they support the party or the person.

Another option would be Meek's method with max keep values.

For example (blanks assumed 1):

A B party supporter might vote

1) A (0.75)
2) B1
3) B2

This means that they are willing to give 0.7 of their vote at most to
candidate A.  If party A vote manages, they can't get more than 0.7 of
that vote.

In effect, the voter has cast 4 votes

A>B1>B2
A>B1>B2
A>B1>B2
B1>B2

This would mean more 'ordinary' methods would still be usable.

It would allow voters to give a fraction of their vote to a candidate
who helped them (people would feel guilty not helping the candidate in
some way).  Also, having the rule would make people aware of the whole
problem in the first place.