Endorsement for STAR voting
Hi folks
I was asked to provide a quote supporting STAR voting by the Equal.Vote
Coalition (equal.vote). The following paragraph is a slightly modified
version of what I wrote to them:
Our "choose-one" electoral system gets a passing grade in democracy, but
just barely. It gets a "D". We can do better. We have the technology. There
are no PERFECT systems, but there are systems that are better than the
systems used in most single-winner, gerrymandered districts. STAR does much
better than passing; it may even get an A or an A+.
I wrote the endorsement because I believe that STAR is a much better
ranking/rating system than "RCV" as currently promoted by FairVote. It's
pretty clear from recent discussion on this mailing list that there are
some folks here that don't believe what the simulations say about approval,
STAR, and other cardinal-flavored voting systems. They don't believe those
simulations, but haven't provided compelling simulations of their own that
show how STAR, approval, or even score voting would be a disaster over the
long haul.
I don't feel comfortable with the strategy burden imposed on voters by
plain "score voting" (a.k.a. "range voting"). Most of us agree that the
best strategy for "score/range" is a "min/max" strategy....basically, turn
the election into an approval election. It doesn't seem fair to have a
system that requires voters who want to maximize the utility of their
ballot to know enough about the system to know the "min/max" strategy.
Even worse, all of the "cardinal" systems (except for approval) require a
much more complicated ballot, just so that people who don't have the
"min/max" decoder ring can give partial credit to some candidates. That's
an awful burden to put on voters for the added complexity of numerical
ballots, when "smart" voters will only vote some variation of "0" or "1".
STAR is not perfect by any stretch of the imagination (c.f. Arrow,
Gibbard). From a complexity perspective, it's tougher than choose-one
voting, since it presents "0" through "5" stars. I suspect SOME of the
strategy problems with plain score/range cause it to be beneficial to
voters to min/max their ballots. But I can't think of any CREDIBLE
electoral scenarios where that would happen. Given that a 5-star STAR
ballot only allows voters to sort candidates into six tiers (gotta love the
fencepost problem),
And this is where the "political science" behind this goes from being
numeric to human and inexact. I think approval voting (with "0" or "1")
presents voters with a choice. Which candidate do I REALLY REALLY want?
Well, I should vote "1" for that candidate. How about another really good
candidate? Well....only if their approval polling is above 20% might I
even risk that. How about a compromise candidate that seems like they have
a good chance of winning? Well, yes, definitely vote for them, since all
of the candidates that I like have only 20% approval (if that) and almost
certainly wouldn't win anyway. Are voters going to get everything they
want? NO. Voters will need to figure out how to compromise with their
neighbors (and housemates, and spouses). There may be some "collusion"
that occurs, but let's not talk about what goes on in peoples' bedrooms.
Let's keep this mailing list clean, okay? :-)
STAR allows for voters to express some nuance, but not too much. "What if I
really really don't like a candidate?", you may ask. Well, don't give them
any stars! Only give stars to candidates you "approve" of (i.e. candidates
you would vote for in an approval-voting election). "Who should I approve
of?" Well, perhaps everyone that you can barely tolerate, such that you
prevent a bad candidate you most fear from winning. If you're not afraid
of the bad candidate (because polling suggests they are under 20% approval
and they seem like a crackpot that has 0% chance of winning), then don't
let that candidate guide your voting.
I think both STAR voting and approval voting in single-winner elections
would have similar effects on the electorate in the long term, and I'm
hoping that at least one of them truly catches on. 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.
Given that approval is in use in two American cities building a track
record (Fargo and St. Louis), and STAR is close to getting approved for use
in Eugene Oregon, I feel like I'm kinda done waiting around for a better
system. I think both STAR and approval voting get an "A" or an "A+" (maybe
93 or 96 on a scale of 0 to 100). I feel like RCV/IRV gets maybe a 61 or a
62 (i.e. barely above choose-one/FPTP, and it may not be better than
choose-one). Since moving to San Francisco (a city which uses RCV/IRV),
I've become MORE afraid of electoral fraud, not less. I've seen what a
goat rodeo the vote counting process has been in SFBay jurisdictions that
use RCV/IRV, so the "precinct summability" argument has had more sway with
me now than it once did.
So, the second paragraph of this email is my endorsement of STAR. I
reserve the right to change my mind, though, so convince me I'm wrong.
Please.
Rob
So I referred to an r/EndFPTP post, but I'll repeat it here.
So the STAR folks make claims of "STAR Voting eliminates vote-splitting and the spoiler effect so it’s highly accurate with any number of candidates in the race." It's just a falsehood.
It's also a falsehood to claim: "With STAR Voting it's safe to vote your conscience without worrying about wasting your vote."
While it's a simple head-to-head election between the two STAR finalists in the runoff (the "R" in "STAR"), the issue is who are those finalists. Same problem as IRV.
So I derived a demonstration case from the Burlington 2009 election. I just scaled it from 8900 voters to 100 and made very reasonable assumptions for how voters would score the candidates. Remember with STAR, the maximum score is 5 and the minimum is 0. To maximize their effect, a voter would score their favorite candidate with a 5 and the candidate they really don't want elected with a 0. The big tactical question is: What to do with the third candidate that is neither my favorite nor my most hated candidate?
L => Left candidate (who was Kiss in 2009)
C => Center candidate (Montroll)
R => Right candidate (Wright)
100 voters:
-
34 Left supporters:
--- 23 ballots: L:5 C:1 R:0
--- 4 ballots: L:5 C:0 R:1
--- 7 ballots: L:5 C:0 R:0 -
29 Center supporters:
--- 15 ballots: L:1 C:5 R:0
--- 9 ballots: L:0 C:5 R:1
--- 5 ballots: L:0 C:5 R:0 -
37 Right supporters:
--- 17 ballots: L:0 C:1 R:5
--- 5 ballots: L:1 C:0 R:5
--- 15 ballots: L:0 C:0 R:5
Now, in the final runoff, the Center candidate will defeat either candidate on the Left or Right, head-to-head.
Score totals:
Left = 34x5 + 15 + 5 = 190
Center = 29x5 + 23 + 17 = 185
Right = 37x5 + 9 + 4 = 198
So who wins? With Score or FPTP, Right wins. With STAR or IRV, Left wins. With Condorcet, Center wins.
Now let's look more closely at STAR. Right and Left go into the final runoff. 49 voters prefer Left over Right, 46 voters prefer Right over Left, so Left wins STAR by a thin margin of 3 voters. But remember, head-to-head more voters prefer Center over either Left (by a 7 voter margin) or Right (by an 11 voter margin). Then what would happen if Center was a finalist in the runoff?
Now those 17 Right voters that had a 2nd-choice preference of Center over Left, what if 6 of them had scored Center a little higher? Like raised the score from 1 to 2? Or if 3 of them raised their scores for Center from 1 to 3? Or if 2 of them raised their scores for Center from 1 to 4? How would they like that outcome?
Or, more specifically, what if the 15 Center voters that had a 2nd-choice preference for Left, what if 6 of them had buried their 2nd-choice and scored that candidate (Left) with 0? How would they like that outcome?
This demonstrates (especially with very realistic election conditions in a close 3-way race) that, because of the Score aspect of STAR, voters need to be thinking tactically whenever there are 3 or more candidates. They must worry about how high to score their 2nd-favorite candidate (or maybe a candidate they dislike less than the candidate they hate). If they score that candidate wrong, they can cause their own candidate to lose or they can cause their hated candidate to win.
But with the ranked ballot, we know what to do with our 2nd-favorite candidate; We rank them #2.
BTW, Approval Voting (used in Fargo North Dakota despite a ruling from the ND Supreme Court in 1911 that would apparently prohibit it) is also a Cardinal method (Approval Voting is a degenerate case of Score Voting with only 0 and 1 as scoring levels). The same tactical voting issue exists when there are 3 or more candidates: Does a voter serve their political interests best by Approving their 2nd-favorite candidate or not approving them?
Lastly, the question I can't get either the STAR or Approval proponents to answer, if the ranked ballots are enough to tell us that and how IRV failed in Burlington 2009 and Alaska 2022 (by not electing the Condorcet winner), why not just use the information provided in these ranked ballots to not fail to elect the Condorcet winner. Why throw the baby out with the bathwater and bring in a completely different system that is also not guaranteed to elect the CW when one exists? It doesn't make sense to me.
--
r b-j . _ . _ . _ . _ rbj@audioimagination.com
"Imagination is more important than knowledge."
.
.
.
Hi Robert,
I've seen you post this example before, but this is the first time I put
some serious brainpower into it. It's good food for thought; I kinda see
how this example results in a form of center-squeeze and how it would
choose a different result than Condorcet methods. My hunch is that there's
"two-dimensional polarization" going on; that is, three tribes of voters in
a triangle rather than "left", "center", and "right", with lots of mutual
distrust between all three. I'm not saying this is unlikely; far from it.
One doesn't need to spend too much time paying attention to global politics
to imagine such a situation.
I'm going to need to get STAR voting implemented in my abiftool software
before I spend much more time thinking about this particular case. I'll
also have to dig up the reddit thread(s) where you posted this, and . Are
you (or anyone on this list) aware of any web software with reasonably
intuitive election markup that implements STAR and a true Condorcet method
or two? I'm probably just going to power through and implement STAR (since
it wouldn't be that tough to add to abiftool), but it's worth knowing who
has implemented both STAR and something Condorcet-y.
Rob
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
I think Kris is mostly correct when he says this:
Over time, this incentive to entry could reduce STAR to Range.
but I see this as intentional. Score and approval are great systems on
their own. They elect Condorcet winners in the presence of strategy, but
score does better than Condorcet if voters are honest. They satisfy
sincere favorite, IIA, and rarely incentivize order reversal. It's hard to
design something better that won't hurt the average voter's brain.
I expect that as soon as STAR is a thing, parties will start nominating
candidates in pairs. This is good; it gives voters more choices. STAR is a
two-step procedure, where first you hold a score vote to pick the
frontrunners (because the first round is score), and then you hold what's
effectively an approval vote to pick the single best candidate.
It's fun to imagine more complex voting systems, but I've come to recognize
an iron law of voting systems: every sufficiently well-designed voting
system converges to score. We have an impossible trilemma:
- 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!) - 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). - 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@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
Election-Methods mailing list - see https://electorama.com/em for list
info
On Tue, Mar 19, 2024 at 14:07 Closed Limelike Curves <
closed.limelike.curves@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:
- 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!) - 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). - 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@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
Election-Methods mailing list - see https://electorama.com/em for list
info
Election-Methods mailing list - see https://electorama.com/em for list
info
I emphasize that I only propose RP(wv) to people & jurisdictions who insist
on ranking, or to political parties who have been offering “RCV” because
progressives want ranking.
Approval is my main proposal.
On Tue, Mar 19, 2024 at 19:54 Michael Ossipoff email9648742@gmail.com
wrote:
On Tue, Mar 19, 2024 at 14:07 Closed Limelike Curves <
closed.limelike.curves@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:
- 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!) - 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). - 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@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
Election-Methods mailing list - see https://electorama.com/em for list
info
Election-Methods mailing list - see https://electorama.com/em for list
info
On 2024-03-19 22:06, Closed Limelike Curves wrote:
I think Kris is mostly correct when he says this:
Over time, this incentive to entry could reduce STAR to Range.
but I see this as intentional. Score and approval are great systems on
their own.
In the mail I responded to, Rob said:
I don't feel comfortable with the strategy burden imposed on
voters by plain "score voting" (a.k.a. "range voting"). Most of
us agree that the best strategy for "score/range" is a "min/max"
strategy....basically, turn the election into an approval
election. It doesn't seem fair to have a system that requires
voters who want to maximize the utility of their ballot to know
enough about the system to know the "min/max" strategy.
So if you agree that STAR will reduce to Range, that's fine, because my
point then stands: if Rob's not comfortable with the strategic burden of
Range, and STAR reduces to Range, then that's a problem for STAR.
They elect Condorcet winners in the presence of strategy, but
score does /better/ than Condorcet if voters are honest. They satisfy
sincere favorite, IIA, and rarely incentivize order reversal. It's hard
to design something better that won't hurt the average voter's brain.
IIA is a means to an end, and that end is that the outcome shouldn't
change if candidates who don't win enter or leave. For Range, although
it passes IIA, we still don't get that end unless the voters' ratings
are calibrated to a scale or scales that don't depend on the candidates
who are present.
How would you suggest that such a calibration be done?
If it can't be done, then Range's IIA compliance, while nice in a
box-ticking way, doesn't really do what it implies it does.
There's a flipside to Range passing all these criteria as well. Since
Range has opportunities for strategy in a large proportion of elections
(see JGA's papers), yet passes a bunch of strategy-related criteria like
pariticipation, weak FBC, etc., that implies that a very large amount of
its strategic potential is concentrated into the question "where do I
put the Approval cutoff" or "how do I set the max and min candidate
ratings". And that's something that even honest voters will have to
contend with, since there are multiple honest ballots.
I expect that as soon as STAR is a thing, parties will start nominating
candidates in pairs. This is good; it gives voters more choices. STAR is
a two-step procedure, where first you hold a score vote to pick the
frontrunners (because the first round is score), and then you hold
what's effectively an approval vote to pick the single best candidate.
It's not so good if you want STAR to be substantively different from
Range, though. And with max-min being the optimal strategy in Range, the
second round would become redundant.
The whole rationale for STAR, as I've understood from its creators, is
to mitigate problems with other methods like Range's max-min strategy.
To quote from the STAR voting paper[1]:
STAR Voting was invented in 2014 with the objective of better
delivering on the underlying goals of voting reform advocates, while
addressing serious issues with Plurality Voting and limitations with
leading reform proposals like Top Two Runoff, Score Voting, and Instant
Runoff Voting (IRV).
It's difficult to "address limitations with ... Score Voting" if the
method is made to reduce to Range itself. So to the degree that is what
it's for, its clone incentive compromises its logic.
It's fun to imagine more complex voting systems, but I've come to
recognize an iron law of voting systems: every
sufficiently well-designed voting system converges to score. We have an
impossible trilemma:
- 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!) - 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). - 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.
You should probably say "cardinal voting theorists have". To pick a few
names, neither Woodall nor Schulze has converged on cardinal voting.
Your observation also ignores, or looks like it ignores the effect of
imperfect information. Suppose that you know that you're going to be a
pivotal voter, and your preferences are A>B>C. You're dropped either
into a universe where A is one full vote short of being the CW
(currently being pairwise tied with B), or into one where B is one full
vote short of being the CW (currently tied with C). The method used to
call the election passes Condorcet, and any ties are broken at random.
If it's the former universe, then your A>B>C vote will make A the CW. If
it's the latter, then it will make B the CW. It's true that in the
former universe, you would want the method to not penalize A if you
compress your A>B>C vote into A>B=C; and in the latter, that it not
penalize B if you compress your A>B>C vote into A=B>C.
However, with imperfect information, you don't know which universe
you're in, so you would want to be able to express your preference both
for A>B and B>C at the same time. Approval doesn't do that. And so
imperfect informaton keeps methods from converging to Approval.
In this veil of ignorance setting, if the method were Approval, you'd
have to gamble and hope you got it right. Since the candidates are a
full vote short, partial rating in Range will have no effect.
Of course, since Condorcet methods are manipulable, this isn't free. You
get funny business in the cycle regime in return for being able to both
maximally support A against B and B against C in the transitive regime.
Methods that fully pass Condorcet fail FBC (though it's possible to pass
Condorcet in the no-truncation case while passing FBC).
I think that shows that the matter isn't as clear cut as the argument
would have it. If invariance to compression destroys this ability to
make an effective vote under imperfect information, that invariance has
a cost, and thus it's not a dominating property in the Pareto sense.
There's no inevitable convergence.
In short, good ranked methods let you direct your voting power
contingent on the state of the election. The cost is that when there's
no obvious way to do so, it can go wrong. Rated methods lack the former
and thus can also do away with the latter.
Strategies like "determine if you should do A=B>C or A>B=C by looking at
the polls" are then workarounds where the voter gets contingent voting
power by estimating the state of the election himself. Manual DSV.
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!
You might be interested in James Green-Armytage's Dodgson-Hare method
which goes outside the box by allowing candidates to withdraw from the
count.[2]
Alternatively, if you really want to go outside the box, drop elections
entirely and do sortition. Do away with the problem. The assembly would
still have to vote on issues, but the participants in an assembly can
discuss among themselves, which would contribute to stability.
There's also Heitzig's randomized consensus methods[3]. These try to
solve the "tyranny of the majority" by using randomness, incentivizing
the voters to find a consensus option. IMHO, they have some problems
with repeated games, and can't be used for big one-shot decisions like
"who should be President this term" due to variance of the outcome; but
they could still be of interest.
Although I don't know enough about the subject to be sure, I suspect
that group strategyproof auction mechanisms would at least be
inefficient.[4] They might not even be possible.
Voting with money would in any case be a bad idea due to income effects,
and even in a generalized sense (if you use "time until you can next
vote" as a proxy for money, say), it could lead to initially successful
voters using their accumulated gains to tilt the playing field. That
voting itself isn't rational may also be a problem: if voters are
incentivized by something else than the chance of being a pivotal voter,
then compensating would-be pivotal voters with near infinitesimal
amounts may not make much of a difference.
-km
[1] WOLK, Sara; QUINN, Jameson; OGREN, Marcus. STAR Voting, equality of
voice, and voter satisfaction: considerations for voting method reform.
Constitutional Political Economy, 2023, 34.3: 310-334.
https://link.springer.com/content/pdf/10.1007/s10602-022-09389-3.pdf
[2] GREEN-ARMYTAGE, James. A Dodgson-Hare Synthesis. Constitutional
Political Economy, 2023, 34.3: 458-470.
https://link.springer.com/article/10.1007/s10602-023-09392-2
[3] https://www.pik-potsdam.de/members/heitzig/maxparc
[4] I'm mostly going on a hunch by analogy to budget neutral
individually strategy-proof mechanisms and one-sided strategy-proof
stable matching mechanisms, none of which are Pareto efficient.
Thinking about IIA, it seems to me that STAR deliberately fails it in a way other methods do not. Condorcet methods fail it because it's unavoidable. Score and approval fail it in practice even if they pass in some theoretical sense, as people would change their scores/approvals with different candidates standing. However, with STAR, say candidate A scores highest followed by B. B then beats A head-to-head and wins the election. But let's say that C enters the race and all the other candidates' scores remain the same. C's total score is between A and B. A then beats C in the head-to-head and wins the election. Also we can imagine that B beats both A and C head-to-head and is the Condorcet winner. In this case, STAR has decided that B need not be compared to A head-to-head because another candidate has an intermediate score. But nothing has materially changed between A and B. This is a failure of IIA caused by a decision to make it happen.
Also on STAR's clone failure - I think Chris Benham previously talked about having an approval cut-off and having the run-off between the most approved candidate and the candidate approved on most ballots that don't approve the most approved candidate (he called it approval opposition). You could also do something similar with the scores. The run-off would be between the highest scoring candidate and the candidate with the greatest "score excess" over that candidate. To measure candidate A's score excess over candidates B, you add up the differences in score between A and B on all the ballots where A outscores B. This is arguably a simple enough change to STAR to make it cloneproof.
Toby
On Sunday, 24 March 2024 at 19:04:05 GMT, Kristofer Munsterhjelm km_elmet@t-online.de wrote:
IIA is a means to an end, and that end is that the outcome shouldn't
change if candidates who don't win enter or leave. For Range, although
it passes IIA, we still don't get that end unless the voters' ratings
are calibrated to a scale or scales that don't depend on the candidates
who are present.
Sorry, I think I gave the wrong impression by mentioning score. Score does
happen to be my favorite system, but a better way to word my comment is
that at some point, if we're comparing score vs. STAR vs. anything Tideman
built, we're talking about methods that can pick the best candidate maybe
95% of the time. It's not about score itself; the point is we're running up
against the limits of what clever mechanism design can really do.
On payment systems: I'm looking at generalized-sense payments. I don't
expect any of these mechanisms to be Pareto-efficient, but the question is
whether we can improve on the status quo of "no trade at all" in a way
that's not catastrophically vulnerable to group strategy, at least.
Here's an example of what I'm talking about: take every race or election on
the ballot. Have people specify their marginal utility of casting an
additional vote, e.g. "I'm willing to give away 1 presidential vote in
exchange for 3 congressional votes." We can use linear programming to find
the market-clearing price for trading votes across races, subject to the
constraint that the total number of votes in each race must equal the total
number of voters, and each voter must have at least 0 votes in each race.
Elect winner by highest score, where each ballot is weighted by the number
of votes they ended up with.
This is a large market with many buyers/sellers of an indistinguishable
good (votes), so the trading prices on votes should end up Pareto
efficient+honest (by the usual welfare-economic theorems about perfect
competition). If I had to take a guess, this is probably a more substantial
improvement in social welfare than the difference between score and ranked
pairs (even though I haven't touched the way we choose winners within each
race).
On Sun, Mar 24, 2024 at 12:03 PM Kristofer Munsterhjelm <
km_elmet@t-online.de> wrote:
On 2024-03-19 22:06, Closed Limelike Curves wrote:
I think Kris is mostly correct when he says this:
Over time, this incentive to entry could reduce STAR to Range.
but I see this as intentional. Score and approval are great systems on
their own.
In the mail I responded to, Rob said:
I don't feel comfortable with the strategy burden imposed on
voters by plain "score voting" (a.k.a. "range voting"). Most of
us agree that the best strategy for "score/range" is a "min/max"
strategy....basically, turn the election into an approval
election. It doesn't seem fair to have a system that requires
voters who want to maximize the utility of their ballot to know
enough about the system to know the "min/max" strategy.
So if you agree that STAR will reduce to Range, that's fine, because my
point then stands: if Rob's not comfortable with the strategic burden of
Range, and STAR reduces to Range, then that's a problem for STAR.
They elect Condorcet winners in the presence of strategy, but
score does /better/ than Condorcet if voters are honest. They satisfy
sincere favorite, IIA, and rarely incentivize order reversal. It's hard
to design something better that won't hurt the average voter's brain.
IIA is a means to an end, and that end is that the outcome shouldn't
change if candidates who don't win enter or leave. For Range, although
it passes IIA, we still don't get that end unless the voters' ratings
are calibrated to a scale or scales that don't depend on the candidates
who are present.
How would you suggest that such a calibration be done?
If it can't be done, then Range's IIA compliance, while nice in a
box-ticking way, doesn't really do what it implies it does.
There's a flipside to Range passing all these criteria as well. Since
Range has opportunities for strategy in a large proportion of elections
(see JGA's papers), yet passes a bunch of strategy-related criteria like
pariticipation, weak FBC, etc., that implies that a very large amount of
its strategic potential is concentrated into the question "where do I
put the Approval cutoff" or "how do I set the max and min candidate
ratings". And that's something that even honest voters will have to
contend with, since there are multiple honest ballots.
I expect that as soon as STAR is a thing, parties will start nominating
candidates in pairs. This is good; it gives voters more choices. STAR is
a two-step procedure, where first you hold a score vote to pick the
frontrunners (because the first round is score), and then you hold
what's effectively an approval vote to pick the single best candidate.
It's not so good if you want STAR to be substantively different from
Range, though. And with max-min being the optimal strategy in Range, the
second round would become redundant.
The whole rationale for STAR, as I've understood from its creators, is
to mitigate problems with other methods like Range's max-min strategy.
To quote from the STAR voting paper[1]:
STAR Voting was invented in 2014 with the objective of better
delivering on the underlying goals of voting reform advocates, while
addressing serious issues with Plurality Voting and limitations with
leading reform proposals like Top Two Runoff, Score Voting, and Instant
Runoff Voting (IRV).
It's difficult to "address limitations with ... Score Voting" if the
method is made to reduce to Range itself. So to the degree that is what
it's for, its clone incentive compromises its logic.
It's fun to imagine more complex voting systems, but I've come to
recognize an iron law of voting systems: every
sufficiently well-designed voting system converges to score. We have an
impossible trilemma:
- 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!) - 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). - 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.
You should probably say "cardinal voting theorists have". To pick a few
names, neither Woodall nor Schulze has converged on cardinal voting.
Your observation also ignores, or looks like it ignores the effect of
imperfect information. Suppose that you know that you're going to be a
pivotal voter, and your preferences are A>B>C. You're dropped either
into a universe where A is one full vote short of being the CW
(currently being pairwise tied with B), or into one where B is one full
vote short of being the CW (currently tied with C). The method used to
call the election passes Condorcet, and any ties are broken at random.
If it's the former universe, then your A>B>C vote will make A the CW. If
it's the latter, then it will make B the CW. It's true that in the
former universe, you would want the method to not penalize A if you
compress your A>B>C vote into A>B=C; and in the latter, that it not
penalize B if you compress your A>B>C vote into A=B>C.
However, with imperfect information, you don't know which universe
you're in, so you would want to be able to express your preference both
for A>B and B>C at the same time. Approval doesn't do that. And so
imperfect informaton keeps methods from converging to Approval.
In this veil of ignorance setting, if the method were Approval, you'd
have to gamble and hope you got it right. Since the candidates are a
full vote short, partial rating in Range will have no effect.
Of course, since Condorcet methods are manipulable, this isn't free. You
get funny business in the cycle regime in return for being able to both
maximally support A against B and B against C in the transitive regime.
Methods that fully pass Condorcet fail FBC (though it's possible to pass
Condorcet in the no-truncation case while passing FBC).
I think that shows that the matter isn't as clear cut as the argument
would have it. If invariance to compression destroys this ability to
make an effective vote under imperfect information, that invariance has
a cost, and thus it's not a dominating property in the Pareto sense.
There's no inevitable convergence.
In short, good ranked methods let you direct your voting power
contingent on the state of the election. The cost is that when there's
no obvious way to do so, it can go wrong. Rated methods lack the former
and thus can also do away with the latter.
Strategies like "determine if you should do A=B>C or A>B=C by looking at
the polls" are then workarounds where the voter gets contingent voting
power by estimating the state of the election himself. Manual DSV.
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!
You might be interested in James Green-Armytage's Dodgson-Hare method
which goes outside the box by allowing candidates to withdraw from the
count.[2]
Alternatively, if you really want to go outside the box, drop elections
entirely and do sortition. Do away with the problem. The assembly would
still have to vote on issues, but the participants in an assembly can
discuss among themselves, which would contribute to stability.
There's also Heitzig's randomized consensus methods[3]. These try to
solve the "tyranny of the majority" by using randomness, incentivizing
the voters to find a consensus option. IMHO, they have some problems
with repeated games, and can't be used for big one-shot decisions like
"who should be President this term" due to variance of the outcome; but
they could still be of interest.
Although I don't know enough about the subject to be sure, I suspect
that group strategyproof auction mechanisms would at least be
inefficient.[4] They might not even be possible.
Voting with money would in any case be a bad idea due to income effects,
and even in a generalized sense (if you use "time until you can next
vote" as a proxy for money, say), it could lead to initially successful
voters using their accumulated gains to tilt the playing field. That
voting itself isn't rational may also be a problem: if voters are
incentivized by something else than the chance of being a pivotal voter,
then compensating would-be pivotal voters with near infinitesimal
amounts may not make much of a difference.
-km
[1] WOLK, Sara; QUINN, Jameson; OGREN, Marcus. STAR Voting, equality of
voice, and voter satisfaction: considerations for voting method reform.
Constitutional Political Economy, 2023, 34.3: 310-334.
https://link.springer.com/content/pdf/10.1007/s10602-022-09389-3.pdf
[2] GREEN-ARMYTAGE, James. A Dodgson-Hare Synthesis. Constitutional
Political Economy, 2023, 34.3: 458-470.
https://link.springer.com/article/10.1007/s10602-023-09392-2
[3] https://www.pik-potsdam.de/members/heitzig/maxparc
[4] I'm mostly going on a hunch by analogy to budget neutral
individually strategy-proof mechanisms and one-sided strategy-proof
stable matching mechanisms, none of which are Pareto efficient.