[EM] Endorsement for STAR voting

[Michael Ossipoff]

On Tue, Mar 19, 2024 at 14:07 Closed Limelike Curves <
closed.limelike.curves at gmail.com> wrote:

>  *every sufficiently well-designed voting system converges to score*.
>

???

:-D
———
Someone in this conversation said that he simplifies the definition of RP
for simplicity. What???

There’s no need to dumb-down or make vague the RP definition. When
proposing RP, I state its actual definition, which is simple, & powerfully,
obviously & intuitively motivated.



We have an impossible trilemma:
> 1. If your voting system doesn't respond to strategic exaggeration, it's
> not responsive to voters. (If you rank a candidate 1st, they damn well
> *should* do better than if you put them in the middle!)
> 2. If it responds to exaggeration but penalizes compression (ranking
> several candidates first makes them less likely to win, compared to ranking
> them all), it's Duvergerian (favorite-betrayal incentive).
> 3. If it responds to exaggeration but doesn't penalize compression, it's
> approval voting (at least if you have strategic voters).
>
> Of these, it seems like voting theorists have converged on #3 being the
> least-bad option, although some systems try to compromise.
>
> STAR tries to compromise between 2 and 3, but mostly sticks close to 3. It
> has a favorite-betrayal incentive, but it's negligible. (Only possible if
> the score-runner-up without your vote would win the runoff, but the
> score-runner-up with your vote would lose). It also gives slight
> decompression at the top end (sometimes you'll want to rate 4 stars instead
> of 5, to make sure your favorite beats your second-favorite).
>
> The only way I can see us moving past this trilemma is if we have some
> outside-the-box mechanism. We can't *just* look at vanilla voting systems
> that pick the best candidate from a pool. We need to look at mechanisms
> that make support costly *across *races or decisions. Voters need to be
> on the hook if they try to just top-rate all their favorites, but that
> incentive has to come from paying a cost somewhere *other* than inside
> the race. If you try to make it costly to support multiple candidates at
> once (like cumulative voting does), you just get favorite-betrayal and
> plurality again.
>
> Improvements on approval voting will probably come from some direction
> like working out how to make the VCG mechanism more resistant to coalitions
> and letting voters rate candidates across multiple races. Most decent
> voting systems are already up against the brick wall of top-shelf methods
> labeled Score/Approval/STAR/RP/Tideman alternative—notice that all of these
> except STAR were proposed more than 30 years ago, all give similar results
> in practice, and we *still* haven't figured out a way to beat them!
>
> On Tue, Mar 19, 2024 at 5:31 AM Kristofer Munsterhjelm <
> km_elmet at t-online.de> wrote:
>
>> On 2024-03-19 02:05, Rob Lanphier wrote:
>> > Hi folks
>> >
>> > I was asked to provide a quote supporting STAR voting by the Equal.Vote
>> > Coalition (equal.vote <https://equal.vote>).
>>
>> [snip]
>>
>> > I think the Condorcet winner criterion (CWC) matters a lot more than
>> > "cardinal" advocates often suggest, but it's almost impossible for me
>> > to imagine a credible election scenario where the STAR winner and a
>> > strictly CWC-compliant method would differ.   More to the point, with
>> that final
>> > pairwise comparison, STAR virtually guarantees that a majority of
>> voters
>> > prefer the winner to the runner up.  And it's 1000% better than RCV/IRV
>> > as promoted by FairVote.
>>
>> The obvious thing that comes to mind that could make STAR fail Condorcet
>> is the clone problem. It doesn't even have to be a deliberate strategy:
>> it could just emerge from the incentives. Suppose that there are three
>> parties: Left, Center, and Right. Say that Left often is the Range
>> winner, but the Left-first voters is a minority so Center comes in
>> second and wins the runoff.
>>
>> Then a second near-Left party has an incentive to grow, because if it
>> can get strong enough, it knows that the left voters will also give it a
>> high rating, so that the runoff now consists of two left-wing
>> candidates, and thus one of them will win. If the rules permit a party
>> to field multiple candidates, then it's even easier: the existing Left
>> party can just field two.
>>
>> Over time, this incentive to entry could reduce STAR to Range.
>>
>> I agree that if we are to take strength of preference seriously (in the
>> vNM sense, as I described in my other post), then it should, as you put
>> it, take nuance into account, but not too much of it. I have some
>> thoughts about how that could be done (I've written posts about it), but
>> the methods would be considerably more complex.
>>
>> Or if you're on the ordinal side of the divide,
>> Smith//Range(renormalized) would fix the clone problem for rated clones.
>> But it wouldn't be monotone.
>>
>> The clone problem and entry incentive could be detected by simulation by
>> replicating James Green-Armytage's work in the paper where he showed
>> that IRV has an exit incentive. To my knowledge, nobody has done so yet,
>> which would explain why you haven't seen any simulations of that form.
>>
>> -km
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