[EM] Quick and Clean Burial Resistant Smith, compromise

[Daniel Carrera]

On Mon, Jan 17, 2022 at 2:48 AM Colin Champion
<colin.champion at routemaster.app> wrote:

> A bit of a side question, but is strategy resistance a good metric to
> quote?
>     FIrstly, you'd never rank methods on it - you'd end up choosing a
> coin toss.
>

It's not my #1 priority, but it seems pretty important to me. Given a
choice between two methods that are equally good in other respects, I would
pick the one where the best strategy is to vote honestly. It's hard to
trust that an otherwise good voting method will produce good results if
people are motivated to lie on their ballots.


    Secondly, voting methods recommended for their resistance to
> tactical voting sometimes have the property that when they go wrong,
> they make larger mistakes than those made by methods targeting sincere
> voting. If you don't take this into account, you can draw misleading
> conclusions.
>

Hmmm... I did not know that. Can you give me an example? Yeah, that sounds
like something we'd really want to avoid.



>     Thirdly, consider a 3-candidate election using IRV. The central
> candidate is the Condorcet winner, but supporters of one of the
> non-central candidates realise that the opposed non-central candidate is
> likely to win owing to the operation of a centre squeeze, and therefore
> compromise on the central candidate. This satifies JGA's definition of
> strategic manipulation but is certainly not an additional fault in IRV;
> on the contrary, it's a mitigation of its weakness under sincere voting.
>

That does sound like a fault in IRV. If the goal is to get the Condorcet
winner (and I agree!) why not use a Condorcet method? The example you cite
is one of my biggest complaints with IRV. If people are driven to vote
dishonestly to compensate for a failure of the system, that tells me that
the method is flawed.



> My own practice has been to measure the performance of methods in the
> presence of tactical voting exactly as I would in its absence, simply
> skipping over any attempted manipulation which doesn't lead to a worse
> result.
>

If two election methods elect the same good candidate, but one of them
achieves that by letting people vote honestly and the other requires people
to learn that they need to manipulate their votes... to me that seems like
a relevant difference.

-- 
Dr. Daniel Carrera
Postdoctoral Research Associate
Iowa State University
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