Condorcet meeting
I notice that RP is the only election method mentioned by name in the
Virginia agenda.
A while ago I ran some simulations on elections with truncated ballots.
Something I noticed was that the presence of RP in the list of methods
made the software unacceptably slow. I didn't look into the cause, but
there's a natural explanation, which is the fact that RP is known to be
NP-complete when it deals correctly with tied margins, i.e. by
exhausting over all their permutations. Presumably if some candidates
are unpopular and ballots are extensively truncated, then tied margins
are much likelier than with complete ballots.
I gather that practical implementations of RP choose a random
permutation rather than exhausting. This seems to me to bring a danger.
The presence of a few vanity candidates (truncated off almost all
ballots) may lead to ties, and this may lead to a comfortable winner
looking as though he owes his victory to a coin-toss. Obviously this
undermines the legitimacy of his win.
CJC
On 9/13/23 09:18, Colin Champion wrote:
I notice that RP is the only election method mentioned by name in the
Virginia agenda.
A while ago I ran some simulations on elections with truncated ballots.
Something I noticed was that the presence of RP in the list of methods
made the software unacceptably slow. I didn't look into the cause, but
there's a natural explanation, which is the fact that RP is known to be
NP-complete when it deals correctly with tied margins, i.e. by
exhausting over all their permutations. Presumably if some candidates
are unpopular and ballots are extensively truncated, then tied margins
are much likelier than with complete ballots.
I gather that practical implementations of RP choose a random
permutation rather than exhausting. This seems to me to bring a danger.
The presence of a few vanity candidates (truncated off almost all
ballots) may lead to ties, and this may lead to a comfortable winner
looking as though he owes his victory to a coin-toss. Obviously this
undermines the legitimacy of his win.
Since RP passes LIIA and Smith, it should be possible to answer such
suspicion by first doing RP, then eliminating every candidate ranked
below the lowest ranked Smith set candidate, and then showing that the
ranking between the remaining candidates does not change.
-km
That's neat. (But... )
CJC
On 13/09/2023 11:35, Kristofer Munsterhjelm wrote:
On 9/13/23 09:18, Colin Champion wrote:
I notice that RP is the only election method mentioned by name in the
Virginia agenda.
A while ago I ran some simulations on elections with truncated
ballots. Something I noticed was that the presence of RP in the list
of methods made the software unacceptably slow. I didn't look into
the cause, but there's a natural explanation, which is the fact that
RP is known to be NP-complete when it deals correctly with tied
margins, i.e. by exhausting over all their permutations. Presumably
if some candidates are unpopular and ballots are extensively
truncated, then tied margins are much likelier than with complete
ballots.
I gather that practical implementations of RP choose a random
permutation rather than exhausting. This seems to me to bring a
danger. The presence of a few vanity candidates (truncated off almost
all ballots) may lead to ties, and this may lead to a comfortable
winner looking as though he owes his victory to a coin-toss.
Obviously this undermines the legitimacy of his win.
Since RP passes LIIA and Smith, it should be possible to answer such
suspicion by first doing RP, then eliminating every candidate ranked
below the lowest ranked Smith set candidate, and then showing that the
ranking between the remaining candidates does not change.
-km
Is that RP(wv), or RP(margins) ?
RP(wv) would thwart & deter offensive strategy, an important property in
public elections.
…&, actually, it seems to me that MinMax(wv) would do that better.
That’s because, choosing only from the Smith Set RP, limits it’s choice to
the strategic top-cycle that created by the offensive strategists.
Suppose that the CW’s preferrers don’t do defensive truncation (never rank
anyone you wouldn’t approve in Approval, or whose preferrers you regard as
likely to offensively order-reverse) ?
Knowing that RP will limit its choice to their small strategic top-cycle,
it would be easier for the strategists to be fairly sur that their
candidate would win in that top-cycle.
But, with MinMax, the winner is chosen more broadly, & could be anywhere in
the candidate-set. …making it more difficult & risky to confidently do
offensive order/reversal.
RP(margins) might the best choice for a completely honest electorate, but
MinMax(wv) seems better for public elections, due to its better thwarting &
deterrence of offensive strategy.
Yes, MinMax doesn’t meet the luxury cosmetic look-good criteria that RP
meets.
But for one thing, I remind you that natural ( sincere) top-cycles are
vanishingly-rare.
So do you want to have less strategy-protection, in order for the result to
maybe look better in a vanishingly rare natural top/cycle?
…& how bad is a violation of Condorcet-Loser anyway. “Beaten by all the
other alternatives” sounds like some kind of unanimity, but of course it
isn’t. It isn’t like a Pareto-violation. I remind you that the MinMax
winner has fewer voters preferring some particular candidate over him than
anyone else does.
Clone-Criterion violation? How bad that really in MinMax, especially when
we’re talking about a vanishingly rare natural top-cycle?
RP(margins) for a completely honest electorate.
MinMax(wv) for public elections.
..& about a primary to reduce the candidates to 5: Forget the primary. If
you think people will have trouble rank-ordering lots of candidates, I
remind you that, to vote among them in a primary, they’d still have to
examine & choose among the initial many candidates.
…harder than ranking only the ones you know & regard as deserving &
definitely in your accepts& preferred set.
On Wed, Sep 13, 2023 at 00:18 Colin Champion colin.champion@routemaster.app
wrote:
I notice that RP is the only election method mentioned by name in the
Virginia agenda.
A while ago I ran some simulations on elections with truncated ballots.
Something I noticed was that the presence of RP in the list of methods
made the software unacceptably slow. I didn't look into the cause, but
there's a natural explanation, which is the fact that RP is known to be
NP-complete when it deals correctly with tied margins, i.e. by
exhausting over all their permutations. Presumably if some candidates
are unpopular and ballots are extensively truncated, then tied margins
are much likelier than with complete ballots.
I gather that practical implementations of RP choose a random
permutation rather than exhausting. This seems to me to bring a danger.
The presence of a few vanity candidates (truncated off almost all
ballots) may lead to ties, and this may lead to a comfortable winner
looking as though he owes his victory to a coin-toss. Obviously this
undermines the legitimacy of his win.
CJC
Election-Methods mailing list - see https://electorama.com/em for list
info
Michael - I don't think I understand everything you're saying. I was
referring to RP (margins), which I believe is the form in which Tideman
specified it, and I assumed that truncation was a mixture of laziness
and ignorance. (Actually the simulation I referred to assumed mandatory
truncation, which I think is common in the US.) I don't hold any brief
for RP; on the contrary I much prefer minimax (also margins).
I do indeed think that voters will have difficulty in rank-ordering
lots of candidates, or even in examining and choosing between them. I
hoped that the primary I proposed would make the best of voters who were
unable to assess the entire field, since if they voted for someone
they'd heard of, and that candidate got eliminated, then their vote
would be transferred to someone they might like, even if they didn't
realise it.
Colin
On 17/09/2023 06:42, Michael Ossipoff wrote:
Is that RP(wv), or RP(margins) ?
RP(wv) would thwart & deter offensive strategy, an important property
in public elections.
…&, actually, it seems to me that MinMax(wv) would do that better.
That’s because, choosing only from the Smith Set RP, limits it’s
choice to the strategic top-cycle that created by the offensive
strategists.
Suppose that the CW’s preferrers don’t do defensive truncation (never
rank anyone you wouldn’t approve in Approval, or whose preferrers you
regard as likely to offensively order-reverse) ?
Knowing that RP will limit its choice to their small strategic
top-cycle, it would be easier for the strategists to be fairly sur
that their candidate would win in that top-cycle.
But, with MinMax, the winner is chosen more broadly, & could be
anywhere in the candidate-set. …making it more difficult & risky to
confidently do offensive order/reversal.
RP(margins) might the best choice for a completely honest electorate,
but MinMax(wv) seems better for public elections, due to its better
thwarting & deterrence of offensive strategy.
Yes, MinMax doesn’t meet the luxury cosmetic look-good criteria that
RP meets.
But for one thing, I remind you that natural ( sincere) top-cycles are
vanishingly-rare.
So do you want to have less strategy-protection, in order for the
result to maybe look better in a vanishingly rare natural top/cycle?
…& how bad is a violation of Condorcet-Loser anyway. “Beaten by all
the other alternatives” sounds like some kind of unanimity, but of
course it isn’t. It isn’t like a Pareto-violation. I remind you that
the MinMax winner has fewer voters preferring some particular
candidate over him than anyone else does.
Clone-Criterion violation? How bad that really in MinMax, especially
when we’re talking about a vanishingly rare natural top-cycle?
RP(margins) for a completely honest electorate.
MinMax(wv) for public elections.
..& about a primary to reduce the candidates to 5: Forget the primary.
If you think people will have trouble rank-ordering lots of
candidates, I remind you that, to vote among them in a primary, they’d
still have to examine & choose among the initial many candidates.
…harder than ranking only the ones you know & regard as deserving &
definitely in your accepts& preferred set.
On Wed, Sep 13, 2023 at 00:18 Colin Champion
<colin.champion@routemaster.app
mailto:colin.champion@routemaster.app> wrote:
I notice that RP is the only election method mentioned by name in the
Virginia agenda.
A while ago I ran some simulations on elections with truncated
ballots.
Something I noticed was that the presence of RP in the list of
methods
made the software unacceptably slow. I didn't look into the cause,
but
there's a natural explanation, which is the fact that RP is known
to be
NP-complete when it deals correctly with tied margins, i.e. by
exhausting over all their permutations. Presumably if some candidates
are unpopular and ballots are extensively truncated, then tied
margins
are much likelier than with complete ballots.
I gather that practical implementations of RP choose a random
permutation rather than exhausting. This seems to me to bring a
danger.
The presence of a few vanity candidates (truncated off almost all
ballots) may lead to ties, and this may lead to a comfortable winner
looking as though he owes his victory to a coin-toss. Obviously this
undermines the legitimacy of his win.
CJC
----
Election-Methods mailing list - see https://electorama.com/em
<https://electorama.com/em> for list info
On 9/17/23 10:25, Colin Champion wrote:
Michael - I don't think I understand everything you're saying. I was
referring to RP (margins), which I believe is the form in which Tideman
specified it, and I assumed that truncation was a mixture of laziness
and ignorance. (Actually the simulation I referred to assumed mandatory
truncation, which I think is common in the US.) I don't hold any brief
for RP; on the contrary I much prefer minimax (also margins).
I do indeed think that voters will have difficulty in rank-ordering
lots of candidates, or even in examining and choosing between them. I
hoped that the primary I proposed would make the best of voters who were
unable to assess the entire field, since if they voted for someone
they'd heard of, and that candidate got eliminated, then their vote
would be transferred to someone they might like, even if they didn't
realise it.
Colin
Here's a thought: does there exist a method that is Condorcet,
cloneproof, yet does not pass Smith? It's probably doable to create one,
but the least contrived ways of getting clone independence do seem to
generate Smith as a "side effect" of sorts. E.g. Schulze and RP.
-km
Hi Colin,
Michael - I don't think I understand everything you're saying. I was
referring to RP (margins), which I believe is the form in which Tideman
specified it, and I assumed that truncation was a mixture of laziness
and ignorance.
I would note, there's another motivation reachable by a simulation, which is quite
reasonable with such methods. Suppose an election is believed to be primarily
between two frontrunners. Then voters might want to resist ranking the worse
frontrunner over anyone else, for the reason that they might be assisting that
candidate, which clearly shouldn't be able to occur if only two candidates are
contenders.
(With WV such truncation solves the issue for the voter. With margins, the savvy
voter cannot conclude truncation is the optimal (or even safe) way to achieve the
same result, and actually this is meant to be a selling point. Though I would argue
that this uncertainty invites the savvy voter to play a dangerous game.
The likely response to my view is that the savvy voter doesn't have enough
information to play the dangerous game. And that's completely right, he doesn't. Yet
he still has to make a decision. Supposedly we should trust that the savvy voter
just votes sincerely and risks handing an advantage to the worse frontrunner. But
that's not at all obvious to me. Something I've said before is that my own
inclination to vote sincerely in a margins Condorcet election would have an inverse
relationship to how robust the method has proven to be in practice.)
(Actually the simulation I referred to assumed mandatory
truncation, which I think is common in the US.) I don't hold any brief
for RP; on the contrary I much prefer minimax (also margins).
I have to say, if a real entity were to enact margins Condorcet with mandatory
truncation, I would find it baffling. One of the few arguments that can be made for
margins is the truncation item above, that a savvy voter can't conclude they should
use it. But with mandatory truncation all voters literally must use it.
[earlier]
I notice that RP is the only election method mentioned by name in the
Virginia agenda.
A while ago I ran some simulations on elections with truncated ballots.
Something I noticed was that the presence of RP in the list of methods
made the software unacceptably slow. I didn't look into the cause, but
there's a natural explanation, which is the fact that RP is known to be
NP-complete when it deals correctly with tied margins, i.e. by
exhausting over all their permutations. Presumably if some candidates
are unpopular and ballots are extensively truncated, then tied margins
are much likelier than with complete ballots.
I gather that practical implementations of RP choose a random
permutation rather than exhausting. This seems to me to bring a danger.
The presence of a few vanity candidates (truncated off almost all
ballots) may lead to ties, and this may lead to a comfortable winner
looking as though he owes his victory to a coin-toss. Obviously this
undermines the legitimacy of his win.
I guess that a real election can tolerate a slow calculation, more than simulations
would want to.
The coin-toss concern is legitimate to me. It might suggest using Schulze instead,
but only on the practical matter, or for transparency (no issues of permutations of
defeats), given that Schulze can still have ties in the final result.
Needless to say, methods should be designed so that vanity candidates (including
even a weak third candidate) don't affect the outcome. The outcome of the most
important single question of the election should be "locked" as quickly as possible
to prevent mischief.
Kevin
votingmethods.net
On Sat, Sep 16, 2023, 9:42 PM Michael Ossipoff email9648742@gmail.com
wrote:
Is that RP(wv), or RP(margins) ?
RP(wv) would thwart & deter offensive strategy, an important property in
public elections.
…&, actually, it seems to me that MinMax(wv) would do that better.
That’s because, choosing only from the Smith Set RP, limits it’s choice to
the strategic top-cycle that created by the offensive strategists.
Suppose that the CW’s preferrers don’t do defensive truncation (never rank
anyone you wouldn’t approve in Approval, or whose preferrers you regard as
likely to offensively order-reverse) ?
Knowing that RP will limit its choice to their small strategic top-cycle,
it would be easier for the strategists to be fairly sur that their
candidate would win in that top-cycle.
But, with MinMax, the winner is chosen more broadly, & could be anywhere
in the candidate-set. …making it more difficult & risky to confidently do
offensive order/reversal.
RP(margins) might the best choice for a completely honest electorate, but
MinMax(wv) seems better for public elections, due to its better thwarting &
deterrence of offensive strategy.
Yes, MinMax doesn’t meet the luxury cosmetic look-good criteria that RP
meets.
But for one thing, I remind you that natural ( sincere) top-cycles are
vanishingly-rare.
This is the same conclusión I have come around to.
And methods that break a three member top cycle at the weakest link tend to
reward the burier faction.
So do you want to have less strategy-protection, in order for the result
to maybe look better in a vanishingly rare natural top/cycle?
…& how bad is a violation of Condorcet-Loser anyway. “Beaten by all the
other alternatives” sounds like some kind of unanimity, but of course it
isn’t. It isn’t like a Pareto-violation. I remind you that the MinMax
winner has fewer voters preferring some particular candidate over him than
anyone else does.
Clone-Criterion violation? How bad that really in MinMax, especially when
we’re talking about a vanishingly rare natural top-cycle?
RP(margins) for a completely honest electorate.
MinMax(wv) for public elections.
..& about a primary to reduce the candidates to 5: Forget the primary. If
you think people will have trouble rank-ordering lots of candidates, I
remind you that, to vote among them in a primary, they’d still have to
examine & choose among the initial many candidates.
…harder than ranking only the ones you know & regard as deserving &
definitely in your accepts& preferred set.
On Wed, Sep 13, 2023 at 00:18 Colin Champion <
colin.champion@routemaster.app> wrote:
I notice that RP is the only election method mentioned by name in the
Virginia agenda.
A while ago I ran some simulations on elections with truncated ballots.
Something I noticed was that the presence of RP in the list of methods
made the software unacceptably slow. I didn't look into the cause, but
there's a natural explanation, which is the fact that RP is known to be
NP-complete when it deals correctly with tied margins, i.e. by
exhausting over all their permutations. Presumably if some candidates
are unpopular and ballots are extensively truncated, then tied margins
are much likelier than with complete ballots.
I gather that practical implementations of RP choose a random
permutation rather than exhausting. This seems to me to bring a danger.
The presence of a few vanity candidates (truncated off almost all
ballots) may lead to ties, and this may lead to a comfortable winner
looking as though he owes his victory to a coin-toss. Obviously this
undermines the legitimacy of his win.
CJC
Election-Methods mailing list - see https://electorama.com/em for list
info
Election-Methods mailing list - see https://electorama.com/em for list
info
Any clone proof method that starts out with ... "Lacking an undefeated
candidate, elect the ..."
For a simple, seamless clone proof, Condorcet Method that fails Smith my
favorite is
Gross Loser Elimination i.e. MinMinPS Elimination:
While two or more candidates remain, eliminate the one with the smallest
Min Pairwise Support.
fws
On Sun, Sep 17, 2023, 3:40 AM Kristofer Munsterhjelm km_elmet@t-online.de
wrote:
On 9/17/23 10:25, Colin Champion wrote:
Michael - I don't think I understand everything you're saying. I was
referring to RP (margins), which I believe is the form in which Tideman
specified it, and I assumed that truncation was a mixture of laziness
and ignorance. (Actually the simulation I referred to assumed mandatory
truncation, which I think is common in the US.) I don't hold any brief
for RP; on the contrary I much prefer minimax (also margins).
I do indeed think that voters will have difficulty in rank-ordering
lots of candidates, or even in examining and choosing between them. I
hoped that the primary I proposed would make the best of voters who were
unable to assess the entire field, since if they voted for someone
they'd heard of, and that candidate got eliminated, then their vote
would be transferred to someone they might like, even if they didn't
realise it.
Colin
Here's a thought: does there exist a method that is Condorcet,
cloneproof, yet does not pass Smith? It's probably doable to create one,
but the least contrived ways of getting clone independence do seem to
generate Smith as a "side effect" of sorts. E.g. Schulze and RP.
-km
Election-Methods mailing list - see https://electorama.com/em for list
info