[EM] Free riding

[Raph Frank]

On Wed, Sep 3, 2008 at 10:51 PM, Kristofer Munsterhjelm
<km-elmet at broadpark.no> wrote:
> In general then, any method that acts like Z had never run (when Z is
> eliminated) would be resistant to Woodall free-riding.

Right, you can get that benefit from alot of methods.  For example,
you could do hand counted PR-STV with the following changes

- restart the count if someone is eliminated (excluding them from consideration)
- the quota is recalculated at each restart

This gets almost all the benefit from Meek's method.
>> There's a risk to the Hylland strategy, of course, if I make a mistake in
>> judging that A will be elected without my help. Other than that, though, I
>> don't offhand see a way of defending against Hylland free riding.
>
> Hmm.. what could be done here? We could try to find out methods that resist
> Hylland free-riding, or find methods where there are few honest reasons to
> use the vote management version.

Ultimately, the problem is that you cannot meet Droop proportionality
without allowing it to some extent.

> For instance, for a 6 candidate case, there's no way the party
> could arrange 720 different pseudo-bailiwicks.

I can't imagine them trying in that case, they likely to just try to
manage first choice vote management.  Maybe, more seats would protect
against vote management.

> There's nothing stopping them
> from doing so, technically, though, and the equal-rank property would make
> it easier for those who actually want to do vote management to do so, as
> they can get the majority to equal rank and then just have a small subgroup
> vote opposite the ordering of the personal voters.

I think if voters were aware of it, they may react by not giving
personal votes to that party.

>
> For the former, I think that Approval methods would have some inherent
> safety against this (simply because you can't reorder the candidates).

You mean proportional approval voting ?

I think that has strategy issues too.

> Schulze's STV is one
> example of such a method. Perhaps one could make a method based on DSC or
> DAC in a similar vein (but not PSC-CLE, it scores badly in my simulations),
> since DAC/DSC works based on sets of candidates.

I wonder if a range ballot would be useful.  The algorithm then
optimally converts it into a ranked ballot.

For example,

1) Each voter submits a range ballot
2) Each voter's algorithm votes for 1 candidate
3) Vote totals are published
4) Repeat step 2,3 say 200 times

Each candidate's score is the sum of votes received in the last 100 rounds.

This allows voters decide if they want to risk it.  If their favourite
is ahead, they might decide to stop voting for him.  However, if they
have rated him much higher than 2nd, they might continue to vote for
that candidate.

I am not sure what algorithms to use in 2), one option is to allow
voters to pick.