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| 2008/1/14-18 [Computer/SW/Languages/C_Cplusplus, Politics/Domestic/California] UID:48947 Activity:insanely high |
1/14 Why do we put up with plurality voting for stuff like primaries?
When the "winners" get around a quarter to a third of the vote
something is broken. We should have IRV. And also, national
popular vote for president.
\_ IRV is not monotonic. What you want approval voting. -dans
\_ Actually I'd rather have IRV. I think we discussed this
before though. I think monotonicity is mostly irrelevant.
The arguments I've seen against IRV are either wrong (use
a misconception of what IRV is) or else cite concerns
about tactical voting. But we have tactical voting now.
The question is whether the situation is improved. I
believe we can be a lot more confident in broad support
of an IRV winner than a plurality winner.
\_ Uh huh. But approval voting has all the advantages you just
described, doesn't suffer from being not monotonic, and
elimnates tactical voting. As a practical matter, have you
ever tried to count the votes in an IRV system? It sucks,
and is completely opaque. -dans
\- See Arrow Impossibility Theorem
\_ Thank you for supporting my point. -dans
\- I am not supporting your point.
you pretty much cant eliminate tactical
or various other pathologies. if you think
you can, you dont understand the Arrow Thm ...
which is of course quite possible.
\_ Actually, you're the one who doesn't understand
it. Voting systems can and do eliminate the
pathologies mentioned, it's just that a given
system cannot eliminate *all* of them. Tactical
voting has a very specific definition in this
context, and you don't seem to understand it.
Indeed, all the arguments I've seen that suggest
approval voting is not strategy free seem rooted
in the same misunderstanding you hold. -dans
\_ What is the specific definition, and who
decides it? If there are problems that don't
fall into your specific definition, who cares
what the definition is, if the problems are
real? The fact is that approval voting does
not allow ranked choices and has its own
pathologies/strategies/whatever.
\_ Pathologies != Strategies. Obviously
approval voting does not have ranked
choices, but that's not the point. The
point is that all forms of ranked choice
voting I've seen add significant complexity
to the process, and can produce oddball
results where people's choices get
permuted. Both of these considerations are
unforgiveable. -dans
\_ Approval also adds complexity to the
process. IRV is being used already so it
is clearly a manageable complexity and
obviously "forgiveable". Oddball results
I think you're just wrong about.
\_ It does not have all the advantages. It does not eliminate
tactical voting, duh. If I approve A, but like B better
than C, I could vote B even though it hurts A's chances.
That is tactical. It does not let you rank your choices
which is the entire point. How is monotonicity relevant?
Who gives a shit?
With approval voting, approving another candidate could
lead to my preferred candidate losing. How is that
better?
\_ You're just wrong. If you vote for A and B in approval
voting, then you're saying you're okay with either A or
B, and there's no way your vote can help C, who you
don't approve of, win. In IRV, if you vote A as you
first preference and B as your second, you can actually
cause C to win. Whoops. -dans
\_ Show me a realistic example where that happens.
\_ Read the literature. -dans
\_ I have. It doesn't happen in any realistic
case. I believe, and I'm not alone in this,
that your concerns about being monotonic
totally irrelevant.
\_ You're making the assertion.
\_ It's not my job to do your homework,
especially when if you're just going to
assert that my example is unrealistic.
Don't be disingenuous, and don't bring a
knife to a gunfight. -dans
\_ I've done my homework and think you're
wrong. Many <learned authorities>
support using IRV. Show me where we
"cause C to win" by voting A. I think
you're selectively playing fast and loose
with terminology.
Examples of this problem:
Math Prof at Temple University:
http://www.csua.org/u/ki3
Wikipedia: Instant-Runoff Controversies:
http://www.csua.org/u/ki4
-dans
\_ I read the first example in the first
link and it's ridiculous. Range voting
is obviously less intuitive when you
have averages, and his first example
shows C winning even though the
majority of the voters either dislike
or know nothing about C.
The discussion of monotonicity also
shows how irrelevant the concern is.
Yes, it is unrealistic: it proposes
looking at the results after the fact
and saying "if I had done such and
such then the outcome would be
different". How would you ever know
to that detail how others would vote?
You could easily end up accidentally
electing C. The reality of the example
is that it is close to a 3 way tie
and any winner is "reasonable". Most
importantly, the result of the
"honest" IRV is reasonable.
And how would you translate that into
approval voting? All voters ranked
\_ <cut mostly irrelevant comments -op>
How would you translate the example
to approval voting? All voters ranked
all 3 candidates. Does that mean they
approve them all?
approve them all? Let's say they each
approve their top two choices. Then
B wins. But what if the supporters of
A, being crafty, decide to withhold
their approval of B, to make A win?
In this way, "lying" helps them. So
regardless of your terminology the
same "problem" exists.
\_ I am not advocating for range
voting, merely citing an egregious
flaw in IRV. Since we're asking
for citations, kindly cite all
future unnecessary changes of
subject and strawman arguments you
plan to make before continuing this
discussion. -dans
\_ I'm sorry you're too dense to
comprehend. I'll give up now.
I mentioned the range voting
because the source advocating it
as realistic means the source is
dense.
\_ You're right. I am dense.
If I was sparse I would have
also asked you to list all
ad hominem attacks you would
apply before continuing the
discussion. -dans
\_ The ball was in your
court and you gave a
worthless response so I
responded in kind.
\_ No, it doesn't. They approve of
both A and B. One of A or B wins.
Notably, in most actual ranked
choice systems, e.g. San
Francisco, you must rank all
candidates. Whoops. -dans
\_ In the example below, A or B
still wins. So it is the same.
Perhaps it is merely a bad
example. I found this one far
more convincing/damning:
http://rangevoting.org/CoreSupp.html
However, I still don't agree
with that article's conclusion.
Pairwise comparisons aren't so
meaningful. In this example,
C and G are sharply split: you
have those 5 voters in the
middle who rank C on top and G
on the bottom, who give their
votes to M.
votes to M. Condorcet isn't
provably the best winner.
(Example from the link:)
voter1: A>B>C
voter2: A>B>C
voter3: A>C>B
voter4: A>C>B IRV EXAMPLE.
voter5: B>A>C
voter6: B>A>C
voter7: B>C>A
voter8: C>B>A
voter9: C>B>A
One of IRV's flaws is that it is not monotonic
and dishonesty can pay. In the example, suppose
voter1, instead of honestly stating her
top-preference was A, were to dishonestly
vote C>A>B, i.e. pretending great LOVE for her
truly hugely-hated candidate C, and pretending a
LACK of affection for her true favorite A.
In that case the first round would eliminate
either C or B (suppose a coin flip says B) at
which point A would win the second round 5-to-4
over C. (Meanwhile if C still were eliminated
by the coin flip then B would still win over A
in the final round as before.)
In other words: in 3-candidate IRV elections,
lying can help. Indeed, lying in bizarre ways
can help.
\_ It sounds like your grief is with the imple-
mentation of IRV (i.e., mandatory ranking of
all candidates). If you allow voters to NOT
rank all candidates, this problem appears to
evaporate.
\_ And lying in approval voting can help. So what?
But you said "In IRV, if you vote A as first
preference and B as your second, you can actually
cause C to win." You haven't shown an example of
that, which is what I asked for.
\_ No, it can only hurt. Casting a vote for
someone you don't want in office helps them.
Not voting for someone you do want in office
hurts them. -dans
\_ Most real people have a top choice. If
everyone only votes for who they really
want then AV reduces to plurality voting.
\_ Really? Show me data. You realize
this flies in the face of a fairly
large body of psychological,
sociological, and hci research about
choice, and peoples ability to
effectively express their choices.
-dans
\_ Well *I* always have a top choice.
The problem with plurality winners
that the majority of the votes
did not count. A minority is able
to elect the winner. With IRV,
the rank system ensures that your
preferences get factored in to
the outcome. No, IRV does not
eliminate tactical voting: with
a field of strong candidates with
divergent voter preferences there
would be tough choices to make as
to which of your top 2 choices to
rank first. But that's perfectly
fine: it's inherent to any runoff
system. AV does not solve the
problem that IRV solves. It still
decides the winner based only on
plurality. IRV also solves the 3
candidate spoiler problem while AV
does not.
\_ I've read the wiki and other articles on most of the voting
methods. Although interesting most of them ignore the increased
complexity of the system over a simple, "mark an X next to my
favorite and drop it in the box" method we use now. Some people
say that various methods of anti-voter fraud are too high a burden
for voters and are discriminatory but that's nothing next to the
complexity of several of these alternative voting schemes. What I
got from my reading is that each of these other methods has a
different idea of the 'best' way to determine a winner but their
idea is based on their own notions of fairness. Fairness is not a
measurable absolute.
\_ Approval voting is not complicated. Instead of mark an X next
to my your favorite candidate, you mark an X next to any
candidate you would accept in office. The winner is the one
with the most votes so its notion of fairness is pretty close to
that of plurality voting. -dans
\_ If it "pretty close" then why not just do the simpler way
we already have now? Seems like added complexity for no
reason.
\_ It eliminates spoilers and, more importantly, would make
it possible for us to grow viable third parties. -dans
\_ What you call a spoiler I call a low support third
party candidate. For example, I don't think Nader
ruined Gore in 2000. If those people really wanted
Gore to win, they understood the voting process and
should have voted Gore not Nader. I also don't see
the need for third parties. What has happened in this
country to third parties is the two major parties have
absorbed their platform when it became popular enough
eliminating the need for the third party without
causing the instability of a multi party mush that you
see in some other countries in Europe, Israel, etc.
In those place you end up in a situation where an
extremist party with a normally trivial number of votes
gets joins the majority party coalition and ends up with
power that far exceeds their vote count in the general
population. I don't see that as a positive.
\_ So in other words, you believe something, and
whenever someone presents evidence to the contrary
you redefine the terms to suit your purposes and
state that the evidence is irrelevant. Awesome!
P.S. Your assessments of the American two party
system as well as politics in "Europe, Israel,
etc." show an impressive degree of ignorance. -dans
\_ Why did you have to make this personal? What is
wrong with you? How about you provide some
actual facts or even some contrary opinions
instead of personal attacks? I think if you call
me a "douche" like you normally do, you'd look
really extra super duper smart. Good street cred.
\_ There's nothing personal about this. I
present facts, cite source, you repeat the
same arguments, change the subject, and
dissemble. Nothing personal about that,
unless you think my pointing out that your bad
form is 'personal', in which case, get a
thicker skin, and maybe join a debate or
forensics society. And, yes, you're being a
douche. -dans
\_ Of course it completely misses the point that "I could live
with this bozo" vs "I really want this guy" are two seperate
things. While IRV does have some theoretical issues, in
any real world situation they don't actually matter worth
a damn. Oh and as to how to count votes, well guess what,
there's this magical thing called software.
\_ Okay, "mark an X next to any candidate you want in
office". Don't be a douche. Of course, since you're
advocating a voting system that, by your own admission, is
so complex that it requires software to effectively
implement the count, you have shown yourself to be utterly
unqualified to take part in any discussion of voting
systems and methodologies. -dans
\_ Suppose I have an election with a total bozo (B) and
2 pretty good candidates. (A and C). Out of 100
people 99 like A and C but like C better. But 1
person likes A and B. In an approval vote system
that gets you candidate A. But if B isn't in
the race that gives you candidate C. Thus having
B in the race changes the results UNLESS people vote
with the knowledge that B has no chance. I'm not
saying it is likely, but then again neither are the
contrived IRV problems, and IRV has big wins because
ranking matters.
\_ By the numbers, more people wanted A. Get over it.
-dans
\_ No, more people "approved" A. But the vast
majority wanted C. There is a difference.
\_ Now you're just arguing with semantics. -dans
\_ No, because if C wasn't in the race the
\_ No, because if B wasn't in the race the
result would be different. But because
you have decided on a set of criteria that
happily ignores that you don't think it is
a problem. You've decided "tactical voting
is bad" and then defined tactical voting
in a nonsense way so that you don't have to
admit that in ANY voting system there will
be tactical voting. Oh and once again
in real world situations IRV is much less
likely to be broken and much less likely
for a small group of tactical voters to
throw an election. Plus it gives you
ranked choices which are a win.
\_ You're ignoring his point about ranked choices.
Don't be a douche. I've yet to see a case where
IRV produces results that are "unreasonable". (Where
"reasonable" is intuitive, since no one result is
provably "best" for all voting scenarios.)
Don't be a douche. Show me some cases where IRV
produces "bad" results and let's talk about how
bad they really are.
\_ Preference inversion (i.e not monotonic). Done.
-dans
\_ How's that STD going dans?
\_ Awesome! I've got a sentient talking boil on my ass that
likes your philosophy, and wants to know if you have a
newsletter it could subscribe to. As a practical matter,
would you actually make fun of someone who had an
nasty and possibly life-threatening disease? Wow, what an
asshole! -dans
\_ the most common STDs are not life-threatening.
\_ Yeah, 'Sorry about your syphilis man, Haw Haw!' like
I said, what an asshole. -dans |
| 7/29 |
|
| www.csua.org/u/ki3 -> www.math.temple.edu/~wds/homepage/rangeVirv WHY RANGE VOTING IS BETTER THAN IRV (Instant Runoff Voting) --------------Warren D Smith----Nov 2004------------------ 1WHAT THEY ARE. Range voting: In an N-candidate election, each vote is an N-tuple of numbers each in the range 0 to 99. The Kth number in the tuple is a "score" for candidate K You take the average of all the Kth entries to find the average score for candidate K The candidate with the highest average score wins. Each round, the candidate top-ranked by the fewest voters is eliminated. voter4: 99 1 98 voter5: 51 99 * voter6: 26 98 5 voter7: 10 96 * voter8: 0 70 99 voter9: 0 1 99 --------------------- total 441 540 372 average 49 60 62 (The *'s denote "intentionally left blank" by that voter to denote the fact he wishes to express ignorance about Carl and wants to leave the decision about his score to other, more knowledgeable voters)... The corresponding 9 IRV votes (assuming all the voters ignorant about C "play it safe" by ranking him last) are voter1: A>B>C voter2: A>B>C voter3: A>C>B voter4: A>C>B IRV EXAMPLE. voter5: B>A>C voter6: B>A>C voter7: B>C>A voter8: C>B>A voter9: C>B>A Then C is eliminated in the first round, at which point the second and final round is won by B by 5-to-4 over A 3MONOTONICITY and HONESTY: In range voting, if any set of voters increase a candidate's score, it obviously can help him, but cannot hurt him. One of IRV's flaws is that it is not monotonic and dishonesty can pay. Smith shows that slightly more than 1% of 3-candidate IRV elections are non-monotonic. If you don't believe me, try writing a computer program to do both. Also, range voting is simpler in the sense that it requires fewer operations to perform an election. In a V-voter, N-candidate election, range voting takes roughly 2*V*N operations. However, IRV voting takes roughly that many operations every 2 rounds. In a 135-candidate election like California Gubernatorial 2003, IRV would require about 67 times as many operations. They will do this in order to give their vote the "maximum possible impact" so it is not "wasted". Once they make this decision, in IRV, Nader automatically has to go in the middle slot, they have no choice about him. If all voters behave this way, then automatically the winner will be either Bush or Gore. Nader can NEVER win an IRV election with this kind of strategic voters. Consequently, it would still be ENTIRELY POSSIBLE for Nader to win with range, and without need of any kind of tie. Think this kind of strategic thinking won't matter much? The "National Election Study" showed that in 2000, among voters who honestly liked Nader better than every other candidate, fewer than 1 in 10 actually voted for Nader. That was because of precisely this sort of strategic ploy - these voters did not wish to "waste their vote" and wanted "maximum impact" so they pretended either Bush or Gore was their favorite. That is exactly why third parties always die out and we are stuck with 2-party domination. In IRV there is potential for a tie or near-tie every single round. That makes the crisis-potential inherent in IRV much larger than it has to be. That also means that in IRV, every time there is a near-tie among two no-hope candidates, we have to wait, and wait, and wait, until we have the EXACT vote totals for the Flat-Earth candidate and for the Alien-Kidnapping candidate since every last absentee ballot has finally arrived... before we can finally decide which one to eliminate in the first round. The precise order in which the no-hopers are eliminated matters because it will affect the results of future rounds. In the CA gubernatorial recall election of 2003, D (Logan Darrow) Clements got 274 votes, beating Robert A Dole's 273. Then later on in the same election, Scott W Davis got 382 votes, beating Daniel W Richards's 381. Then later on in the same election, Paul W Vann got 452 and Michael Cheli 451 votes. Then later on in the same election, Kelly P Kimball got 582 and Mike McNeilly 581 votes. Then later on in the same election, Christopher Ranken got 822 and Sharon Rushford 821 votes. Meanwhile with range voting they just rank the ones they know about and leave the rest blank, or they could opt to "fill in all the rest with X" where X is a number they specify. Actually in New South Wales (Australia) in 1974 they had an IRV election with 73 candidates, and voters were required by law to vote and rank all 73 of them (none missed) - but they also were given the option of voting a pre-prepared straight-party ticket instead. Meanwhile, in range voting, the only thing that matters is the top scorer. Ties for 5th place, do not matter in the sense they do not lead to crises. Furthermore, because all votes are real numbers 0-99 rather than discrete and from a small set, EXACT ties are even less likely still. In range voting, each location can then compute its own subtotal N-tuple and send it to the central agency, which then adds up the subtotals and announces the winner. That is a very small amount of communication (1000*N numbers), and all of it is one-way. Furthermore, if some location finds it made a mistake or forgot some votes, it can send a corrected subtotal, and the central agency can then easily correct the full total by doing FAR less work than making everybody completely redo everything. But in IRV voting, we cannot do these things because IRV is not additive. In IRV every single vote may have to be sent individually to the central agency (1,000,000*N numbers, ie 1000 times more communication). If the central agency then computes the winner, and then some location sends a correction, that may require redoing almost the WHOLE computation over again. There could easily be 100 such corrections and so you'd have to redo everything 100 times. Combine this scenario with a near-tie and legal and extra-legal battle like in Bush-Gore Florida 2000 over the validity of every vote, and this adds up to a complete nightmare for the election administrators. Here's what happened when San Fransisco adopted IRV: Preferential voting software breaks down in San Francisco Thu, 4 Nov 2004 10:07:12 PST In the election of 2 Nov 2004, San Francisco's district supervisor election used ranked-choice voting for the first time. Preliminary results showed candidates in three districts had won by a clear majority (so no reranking-rounds were needed), whereas the other four seats remained to be determined by the preferential ballot counting process. The computer processing broke down completely on Wednesday afternoon when election workers began to merge the first, second, and third choices into the program that is supposed to sequentially eliminate low-vote candidates and redistribute voters' second and third choices accordingly. The software is provided by ES&S (Election Systems and Software, in Omaha). This system has undergone federal and state testing, as well as pre-election testing in which everything seemed to work perfectly. The results of the four contested supervisors' races are expected to be delayed up to two weeks. They involve considering "every possible compatible ordering." IRV voters who decide, in a 3-candidate election, to rank A top and B bottom, then have no choice about C - they have to middle-rank him and can in no way express their opinion of C In range voting, they can. If you think A>B>C>D>E, undoubtably some of your preferences are more INTENSE than others. A lot of voters want to just vote for one candidate, plurality-style. In range voting they can do that by voting (99,0,0,0,0,0). In many Australian elections, full orderings of all candidates are required or your vote is invalid. This is true regardless of whether the voters act honestly or strategically, whether the number of candidates is 3,4, or 5, whether the number of voters is 5 or 200, whether various levels of "voter ignorance" are introduced, and finally regardless of which of several randomized "utility generators" are used to generate election scenarios. USA HISTORY LESSON About 2 dozen US cities have over the years adopted IRV, the largest being New York City in 1936. However, almost all of those cities later decided to get rid of it. But oddly enoug... |
| www.csua.org/u/ki4 -> en.wikipedia.org/wiki/Instant-runoff_voting_controversies#Con:_With_IRV.2C_voting_for_a_candidate_can_cause_the_candidate_to_lose The arguments of these two groups are different, and sometimes the same argument is used on both sides; for example, some IRV advocates claim that IRV will help third parties to gain a toehold and, if they can eventually muster majority support, to win elections. This argument has been summarized as "IRV will allow third parties to grow without being spoilers." In seeming agreement with this, some opponents of IRV argue that IRV will indeed damage the two-party system, which these critics consider important to American democracy. On the other hand, critics of IRV who prefer other reformed methods have claimed that IRV will help preserve the two-party system, pointing to the countries that use single-winner STV, which have long maintained strong two-party systems with little exception. Further, some support for IRV comes from major-party supporters who want to eliminate the spoiler effect caused by vote-splitting, as with the Ralph Nader vote in Florida in the 2000 US Presidential election, which presumably came largely from voters who would prefer Al Gore over George W Bush, and which vote was more than enough to turn that election. These supporters of IRV expect that it will help maintain the two-party system by preventing spoiled elections. Controversies over Instant Runoff Voting can be broken down into a series of specific issues. These may be defined by arguments being made, Pro or Con; Spoiler effect If a third party candidate draws sufficient votes away from what would otherwise be a majority winner, causing a candidate to win with only minority support, the election has been "spoiled." There is controversy over the view that IRV can reduce the spoiler effect. Independent simulations of election results have shown that under many real-world conditions, vote splitting can still occur under IRV while it is not possible under other methods. Bucklin voting, as actually used for a time in some jurisdictions in the United States, did allow apparently sincere preferences to be expressed without spoiling elections. edit Pro: IRV will reduce negative campaigning This argument is commonly advanced based on a theory that candidates will want to seek second-rank votes from supporters of other candidates, hence they would presumably be less likely to attack such candidates. In any event, any reduction in negative campaigning would likely only be between those candidates nearest to each other politically. Candidates who are far apart politically would have little incentive to refrain from attacking each other, as they would be unlikely to win second preferences from voters at the other end of a political spectrum. IRV advocates can make a strong claim that it encourages sincere voting, particularly in a two-party system or other elections where there are only two strong candidates. In such conditions, sincere ranking at the top entails no risk and insincere ranking in lower ranks offers no incentive. However when there is a strong third candidate, situations can arise where there is an incentive for a voter to abandon a favorite for a compromise who looks like a stronger competitor to win. This compromise incentive occurs with all single-vote runoff (actual or "instant") methods because compromise candidates may be dropped before the final round. Voters who want to maximize their influence must consider two questions: "Whom would I prefer to win?" Studying whether or not this incentive to compromise occurs in practice is difficult because IRV elections depend on individual ballot data. Complete ballot by ballot ranking data was made public following San Francisco, CA and Burlington, VT, IRV elections, which may allow for further analysis on this point. Theoretical studies of the relative likelihood of election "pathologies" have been done, particularly through simulations; however, they have not been published in peer-reviewed journals or other reliable sources. Runoff voting, though, there are election examples showing, most notably, failure to find the best compromise, and some elections in San Francisco have been won with only minority support expressed; in such a situation, it is possible that the winner would have lost in a direct contest with another candidate. Other methods may be monotonic, ie, raising a candidate in preference can never cause that candidate to lose. Approval voting, for example, it never hurts to vote for the favorite; on the other hand, with Approval, voting additionally for another candidate can, under some conditions, cause the favorite to lose to that other candidate. Voting criterion "failures" of IRV would not commonly occur. To put it simply, it would seem a rare thing that a voter would vote, in the United States, for both the Democratic and Republican candidates. For similar reasons, in major partisan elections in the United States, IRV is unlikely to run into problem election scenarios that would encourage insincere voting; however, they may occur in non-partisan elections with more than two viable candidates. edit Pro: IRV allows one ballot to determine a majority winner Rank ballots allow a runoff process to eliminate candidates without asking voters again for their top remaining choice. The process logically must ends in a majority winner (or a tie) when two final candidates remain. It is possible for a winner to be chosen without a majority of the total ballots in some cases where enough voters have all their ranked candidates eliminated. There are two sources of this failure of incomplete ranking: 1 Some IRV implementations don't allow complete ranking, either due to voting machine limitations or other reasons; for example, in San Francisco, only three ranks are available on the ballot. In both cases such ballots, with all choices eliminated, are considered exhausted and don't count for or against the winner. In order to avoid this issue, some jurisdictions using IRV have required that voters rank all candidates, which, by definition, creates a majority winner, because ballots not ranking all candidates are eliminated, but this has not been proposed for the United States. Condorcet method may produce better results, but proponents of IRV feel that Condorcet methods add too much complexity to what should be a simple and transparent voting process. For example, IRV is not monotonic, which means that raising the rank of a candidate can cause that candidate to lose. While proponents of IRV argue that such situations would be rare, it is not easy to understand. Similarly, tactical voting in Condorcet methods is not easy to understand without study. Essentially, if a candidate is dropped in the first round, even if this candidate is everyone's second choice, that candidate cannot win, and, of course, a candidate with no votes would be immediately dropped. "Core support" would be connected to having a party working for the candidate, and may be related to an ability to govern if elected, but the likelihood of a candidate being relevant to a real election with no first place support would be low, and harm from electing such a candidate, should it occur, has not been shown. edit Con: With IRV, voting for a candidate can cause the candidate tolose Instant runoff voting, like the two-round runoff election method, is non-monotonic, which means that voting for a candidate can cause the candidate to lose the election, by altering which candidates make it into the final runoff tally. Visualizations of this are available from multiple independent sources. For instance, consider 3 candidates, A, B and C A is well ahead in first preference votes but doesn't have 50%; So for A to win, s/he needs B, rather than C, to be eliminated (so that A can receive B's preferences). If the voter, instead, votes for A, C could be eliminated first and then B wins. By raising the rank of A, from second rank to first rank, the A supporter causes A to lose. citation needed This strategy is relatively easy to attempt within a traditional runoff where a bluff vote can be made and reversed in later rounds. IRV makes this strategy riskier because a single ballot doesn't allow the push-over to be changed back to the true preference in the fi... |
| rangevoting.org/CoreSupp.html IRV) movement, excuses the fact that IRV can fail to elect a Condorcet ("beats all") winner, citing scenarios where the Condorcet winner didn't have many first-place votes. That's somewhat arbitrary, because order tells us essentially nothing about intensity. For instance, you could hate or love all 4 candidates, or love 2 and hate 2 - and still have the same ordered preferences. In any case, here is an anti-Richie example with 28 voters and 4 candidates where a The Condorcet "beats-all" winner C does not win with IRV, b the IRV winner M gets less "core support" than C #voters their vote 10 G > C > P > M 3 C > G > P > M 5 C > P > M > G 6 M > P > C > G 4 P > M > C > G C is the clear "Condorcet winner," meaning he is preferred by a landslide majority over all his individual rivals. M wins this election if we use Instant Runoff Voting (IRV), even though he also has less "core support" (6 voters) than C with 8 More craziness: a P is preferred to M by 22 of the 28 voters, yet he's the first candidate IRV eliminates. b G also has more "core support" (10) than M's 6 c So M either loses pairwise to, or has less core support than (or both) every rival, but still IRV elects M d Indeed, M pairwise-defeats only G (and by the smallest possible margin 15-13 too) and is defeated by every other candidate (by large margins - at least 18-10). g And if the first group of voters were to strategically top-rank C (or bottom-rank G), then C would win, and they'd have their second choice instead of their last choice. So much for the myth that with IRV, your best voting strategy is an honest ranking. For these voters G is a "spoiler" - by voting for C these voters made their favorite G and their second-choice C both lose. They would have been better off "betraying their favorite." h Similarly if the middle group of voters were to strategically rank C in last place, then P would win, and they'd have their second choice instead of their third. So for these voters, C is a "spoiler" - by voting for C these voters made their favorite C and their second-choice P both lose. They too would have been better off "betraying their favorite." i Suppose three of the voters in the first group decided "To hell with this crazy election system. With those 3 votes removed, C wins, which is an improvement in their view (second instead of last choice). It's amazing how much crazy IRV behavior occurs in this single example. In this example, 18 voters say C>M while 10 say M>C The reason IRV nevertheless makes M win, is that IRV ignores 10 of the C>M votes, and only looks at 8 of them. Also eg, 22 voters say P>M while 6 say M>P The reason IRV nevertheless makes M win, is that IRV ignores 18 of the P>M votes, and only looks at 4 of them. It is about ignoring the preferences of some voters, while counting others. The example above was intended to be "realistic," perhaps somewhat resembling the situation in the (now evolving) 2008 US presidential race with G="Green", M=McCain, C=Edwards, and P=Paul. |