Hello,
Since I regard "IRV" (the Alternative Vote, unlimited strict
ranking "version") as
one of the good methods, the best in my judgement of the methods that meet
Later-no-Harm, I am encouraged to respond to Kathy Dopp's anti-IRV propaganda
piece.
Some Fairness Principles for Voting MethodsConditions have been proposed to
judge
whether or not voting and vote-counting methods result in fair or in non-fair,
paradoxical
election results.
1. The addition of an alternative (candidate) who does not win should not
affect the outcome.
If you have an election contest where candidate A wins, and you introduce a new
candidate C,
then either candidate A should still win, or candidate C should now win. In
other words, spoilers
should not be possible or the addition of an alternative (or candidate) that
doesn't win should not
affect the outcome.
This is some times called "independence of irrelevant alternatives" that says
that the collective
preference order of any pair of alternatives x and y must depend solely on the
individual voters'
preferences between these alternatives and not on their preferences for other
irrelevant (nonwinning)
alternatives.
IRV does
elections where "spoilers" determined who won, neither does the existing
plurality voting
method meet this condition.
do seem to meet this fairness condition.not meet this condition of fairness.
(See appendix A.) As we’ve seen from prior U.S.ix Other alternative voting
methods, such as approval or range voting
In practical effect *no* method meets this.Approval and Range can be said to
meet
Independence of Irrelevant Alternatives (IIA) only if the votes are interpreted
as the voters giving
ratings on some fixed scale that is independent of the actual candidates.
On this perverse interpretation Approval and Range do not reduce to FPP in the
2 candidate election,
in violation of Dopp's "fairness principle 4":
.Any candidate who is the favorite [first] choice of a majority of voters
should win
I don't see what IIA actually has to do with "fairness". To me it is only about
congruity or
mathematical elegance.
2.
must be preferred to alternative y in the collective preference order
result]. This is some times called the "Pareto condition" that says whenever
all individuals prefer
an alternative x to another y then x must be preferred to y in the collective
preference order. It is
possible to find examples of when IRV and plurality voting violate this
fairness condition.Whenever all individuals prefer an alternative x to another
alternative y then alternative xx [the final election
No it isn't. And why in a single-winner election method do we care about the
whole "collective
preference order" instead of just the winner?
(See appendix B.)
There is no example of IRV or plurality voting failing Pareto in appendix B,
only one of Approval
meeting it.3. The candidate who wins should have received a majority of voters’
votes.Some jurisdictions require winning candidates to have a majority (more
votes than 50% of the
ballots cast by voters).
Maybe so, but should they? I gather that if this requirement isn't met, the
decision on who
fills the office is taken out of the hands of the voters. Some voting methods,
such as plurality voting and IRV
condition. Actual top-two runoff elections do.do not meet this
Only if "voters" means only those who showed up for the second round. Say in a
3 candidate
election, I can't see any justification for making this big distinction between
a "majority" in the
second round of Top-Two Runoff (TTR) and the majority of voters who
participate in the
second round of IRV.
Kathy, do you insist that the election method requires voters to make second
trip to the polls
whenever the first doesn't produce a winner who "receives a majority of voters'
votes"?
Two-round methods can have their plusses, but in general I think it is more
appropriate to
compare IRV only with other decisive single-round methods.
But while we're here, IRV (Alternative Vote, unlimited ranking) dominates TTR
in terms of
criterion compliances, including those that relate to "majority rule". Both
TTR and IRV
meet Condorcet Loser, but IRV (Alt.V, unlimited ranking) has the extra
advantages over
plurality voting (FPP) of meeting Majority for Solid Coalitions (aka Mutual
Majority), Mutual
Dominant Third, and Clone-Winner.
4.
IRV does not always pick a majority winner out of all ballots cast, IRV
proponents emphasize
that
candidate as the winner. However, the existing plurality voting method also
meets this condition,
which IRV proponents call the "majority criteria".Any candidate who is the
favorite [first] choice of a majority of voters should win. Whileif a majority
winner exists among voters’ first choices, then IRV will always select this
I think some call this the "Majority Criterion" ("criteria" is the plural of
*criterion*). I and others
prefer the name "Majority Favorite". It isn't of much idependent theoretical
interest to me. It
is implied by Majority for Solid Coalitions and Mutual Dominant Third, which
are met by IRV
(Alt.V,unlimited ranking) but not TTR. Also it is implied by the Condorcet
Criterion.
It is FPP's one redeeming feature compared to Approval (and more clearly,
Range). It is failed
by Borda.Range and approval voting do
That's right. Obviously this has to be the case to maintain compliance with
Later-no-Harm.
Kathy, is Majority Favorite a "fairness condition" you support or not?
The pair-wise favorite among all voters should be the winner. In other words,
the candidatenot meet this condition.
This is the Condorcet criterion. It is a strict technical pass/fail test. I
agree that it is good for
methods to meet it, but it is incompatible with both Later-no-Harm (as met by
IRV and FPP)
and Favorite Betrayal (as met by Approval, Range, and a version of Bucklin).
In my book a method can fail the Condorcet criterion and still qualify as
"good" if it meets
some useful criterion that is incompatible with it.So, IRV does
methods are available that meet more of these fairness conditions.not meet four
out of the above five fairness conditions and other alternative voting
This is a very weak argument. There are very many
reasonable/interesting/plausible standards/
criteria/properties that have been applied to assessing voting methods one
could select from
to present an arbitrary list of "five fairness conditions". For any method it
is very easy to make
such a list so that the method only scores 2/5.
This particular list is a very unimpressive grab-bag. The first two have been
inappropriately
borrowed from Arrow's Impossibility Theorem. The first is (in practical
effect) met by nothing
and the second is met by every remotely reasonable deterministic method.
The third is something very silly that no decisive one-round method that allows
truncation can
meet. The fourth is is very untaxing, and mainly of some interest to
supporters of IRV and
FPP who dislike Range and Approval.
The fifth is serious. It implies the fourth.
If these five were the only possible "fairness conditions" or clearly the most
important and it
was obvious that they should be given approximately equal weight, then IRV's
low score of 2
(not 1) out of 5 might suggest that it isn't a good method.
Probably more later,
Chris Benham
http://electionarchive.org/ucvAnalysis/US/RCV-IRV/InstantRunoffVotingFlaws.pdf
© 2008 Kathy Dopp/National Election Data Archive. A non
royalty bearing license allowing one time use of this material is granted,
under the condition that a copy of whatever use
is made of this material is sent to [EMAIL PROTECTED] and [EMAIL PROTECTED]
when it is first disseminated,
and full attribution is made to Kathy Dopp/National Election Data Archive along
with this document’s Internet URL
5.
preferred when compared pair-wise over other candidates by the most number of
voters should
win. This is called the Condorcet winner. Both plurality and IRV do
Range and approval voting meet it more often, as in the examples in appendix
A.not meet this criterion. The majority criterion candidate wins in
IRV even if the candidate is the last choice or disapproved of by all other
voters, and even if there
is an alternative candidate who is approved of by all voters.
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