[EM] Re: [instantrunoff] Drafft of CVD analysis about IRV vs. Condorcet Voting

[Dave Ketchum]

On Fri, 2 Apr 2004 10:11:03 EST democracyusa at aol.com wrote on instantrunoff:

> Greetings,
> 
> As advocates of instant runoff voting, we have tried to focus on the 
> case for instant runoff voting over the plurality and delayed runoff 
> systems already used in the United States. But as many of you may know, 
> some of our most vigorous opponents are supporters of other single 
> winner reform approaches. We wish they would focus their energy on 
> seeking support for their system compared to plurality and runoffs, as 
> we do. Some indeed do that, but it hasn't been the case for others.
> 
> There are good reasons for why we support instant runoff voting over 
> alternatives. The analysis below is in draft form, and Terry Bouricus 
> (tbouricius at verizon.net) is our point-person in finalizing it. If you 
> have any comments or suggestions, please let him know. Note that when we 
> post it on the web, we will have a short summary for those who don't 
> want to get into as much detail.
> 

Others have noticed this post, and written about it on election-methods. 
There Condorcet AND IRV are recognized as better than competitors such as 
Plurality.  I will try for more detail, as a Condorcet backer.


> - Rob Richie
> 
> ########
> Instant Runoff Voting vs. Condorcet Voting
> 
> Among proposals to reform the way we elect single-winner offices, 
> instant runoff voting (IRV) is by far the most popular and has gained 
> significant traction in states and cities around the nation. But there 
> is persistent criticism of IRV by some advocates of other alternative 
> voting methods. This analysis compares IRV with Condorcet voting, a 
> ranked-choice system favored by some mathematicians. We conclude that 
> IRV is better than Condorcet voting both for theoretical and pragmatic 
> reasons.
> 

Certainly IRV has LOUD VOCAL backing.

Note that Condorcet and IRV use identical ballots and usually agree as to 
winner - only cases where they disagree provide ammunition for debate.


> As a first overall point, Kenneth Arrow won the Nobel Prize in part for 
> proving that every single-seat election system inevitably violates some 
> reasonable measure of "fairness," in at least some circumstances. It 
> therefore is possible to find a flaw in every method of voting. That is, 
> there is no such thing as a perfect voting system -- one must assess how 
> harmful and how frequent the "pathological" outcomes will be under each 
> system, and how each system will enhance or worsen campaigns and 
> political discourse.
> 
> A second general point is that there are two fundamental classes of 
> voting systems that fulfill different purposes. IRV, Condorcet voting 
> and all systems for electing offices in which only one person wins (such 
> as a mayor, governor, president or a legislator representing a 
> single-member district) are "winner-take-all" systems. No 
> winner-take-all system is ideal for electing a legislative body, such as 
> a city council, or state or national legislature. In those cases, some 
> form of full representation (also called proportional representation) is 
> more representative. Full representation voting systems assure that the 
> majority of voters will elect the majority of the legislative seats, but 
> also, that significant minorities will be able to elect their fair share 
> of seats (in proportion to their support among the electorate). The 
> discussion below is limited to a comparison of two single-seat 
> majoritarian winner-take-all systems - IRV and Condorcet.
> 
> Turning to single winner elections, then, we believe that there are 
> several voting methods that would better serve the public interest than 
> traditional plurality methods. We focus our reform energies on IRV 
> because we believe it is the best of these systems and one with strong 
> political potential in the United States. See our extensive webpages 
> describing IRV. [LINK ON SITE TO www.fairvote.org/irv]
> 
> Like IRV, Condorcet voting is an "ordinal" system in which voters rank 
> candidates. Candidates are compared on every person's ballot, and the 
> candidate who theoretically could defeat all other candidates in 
> one-on-one races based on these pair-wise comparisons is declared the 
> winner. If there is no such candidate, (such as Candidate A beats 
> Candidate B, Candidate B beats Candidate C, but C beats A) some fallback 
> system, such as IRV, must be used to select a winner.
> 

Condorcet backers recognize this problem and debate as to solutions. 
Usual method is to disqualify the "weakest" of the conflicting pairs, 
rather than involving some other method such as IRV.


> Both IRV and Condorcet provide these improvements:
> 
> 1. They prevent the election of a candidate whom the majority thinks is 
> the worst choice (a quite plausible occurrence under plurality voting in 
> a three-way race).


Time to throw rocks.  Assume 40 like A; 60 like B, seeing A as worst 
choice; and 31 of the 60 are enchanted with C as EVEN BETTER than B.  Laid 
out more formally (note that, as I would expect, these voters ONLY vote 
their serious positive interests):
      40 A
      31 C>B
      29 B

Condorcet will see 60B>40A, 40A>31C. and 31C>29B.  I expect the C>B to be 
discarded as weakest, declaring B as winner.

IRV must discard the 29 B as weakest, after which the unwanted A becomes 
the obvious winner.


> 2. They accommodate more parties and candidates, by eliminating the 
> "spoiler" issue for parties that cannot yet gain enough votes to win. 
> Having more choices from across the spectrum deepens political 
> discussion and allows new parties to disseminate their message and grow 
> (or not) organically over a period of years.
> 

Mostly agreed - note that C becomes a "spoiler" for IRV above.

Also note that multiple candidates competing for the same voters is not 
the disaster that it can be in Plurality.


> Condorcet advocates suggest that it has advantages over IRV. For 
> example, in some rare cases a voter in an IRV election can hurt a 
> candidate by ranking that candidate more highly. Although technically 
> true, its importance is negligible because such a rare mathematical 
> possibility is almost impossible to anticipate before an election and 
> thus of no tactical significance. One would have to know that one of 
> your more favored candidates would be been benefited by the elimination 
> of one of your more disapproved candidates before a later runoff round 
> of counting. In decades of important IRV elections in Australia and 
> Ireland, this alleged flaw in IRV has caused no problems or 
> controversies - and is no different from the Monday morning 
> quarterbacking one can do under any election system.
> 
> IRV critics who prefer Condorcet also point out that in some scenarios, 
> voters in an IRV system could improve the chances of their second 
> favorite candidate defeating their least favorite candidate by 
> strategically ranking their second choice as number one instead of their 
> true favorite candidate (assuring the strongest acceptable candidate 
> makes it into the final runoff count, for example, ahead of a candidate 
> whom many people like better, but does not have enough centrist appeal 
> to win in a runoff). Because of this example they argue incorrectly that 
> Condorcet voting is the only system that escapes 100% from insincere 
> strategic voting and from the spoiler problem.
> 
> In fact Condorcet also creates incentives for insincere voting. All the 
> mathematical elegance of Condorcet Voting is irrelevant when it can be 
> so obviously gamed through insincere strategic voting. Strategic voting 
> occurs when voters have an incentive to rank candidates in an order 
> contrary to their true preferences in order to help a preferred 
> candidate or block another candidate.  Although strategic voting may be 
> possible with any voting system, it is in fact a larger problem with 
> Condorcet than with IRV. 
> 

Huh!


> Suppose four candidates (A, B, C, and D) are running for an office, 
> where candidates A and B are the frontrunners.  Consider a voter whose 
> true preferences are in order of A, B, C, D.  Under Condorcet, by voting 
> insincerely this voter can minimize the chances that candidate B will 
> defeat his or her preferred candidate A. A voter quickly realizes that 
> the best strategy is to punish the strongest competitor to her favorite 
> candidate by ranking the candidates insincerely A, C, D, B. Doing so may 
> block B - and any candidate -- from becoming the Condorcet winner and 
> improve candidate A's chances to win under the fallback rule. Worse yet, 
> if both A and B supporters widely engage in such strategic voting, the 
> winner could be a candidate most voters actually oppose, but didn't 
> realize would benefit from their insincere rankings. With IRV, there 
> rarely is an incentive to engage in strategic voting, since later 
> rankings do not hurt earlier rankings.  In certain unique situations 
> where there is widespread availability of detailed polling information, 
> there are ways to vote strategically with IRV, but strategic voting is 
> greatly limited. There is no rule of general applicability of the value 
> of insincere rankings, as there is with Condorcet.
> 

Huh!  By ranking A first the voter has said as much as possible as to A vs 
B.  Ranking A,C,D,B in Condorcet ONLY indicates liking C and D better than 
B - doing that if you do not dislike B that much is a stupid 
misunderstanding of strategy.


> Condorcet has even more important negatives directly related to its 
> seemingly sensible goal of selecting the candidate who theoretically 
> would beat all others in a one-on-one race. Its biggest flaw is that it 
> can elect a candidate who has too little support to be seen as a good 
> representative of substantial numbers of voters - a candidate so lacking 
> in support to ever be competitive in a traditional plurality or runoff 
> election. At an extreme, the Condorcet winner in a four-candidate race 
> might be unable to win a single vote in our current election system, but 
> could win under Condorcet by avoiding being any voters' last choice. In 
> other words, the Condorcet winner's ability to defeat all other 
> candidates in a one-on-one race is entirely theoretical because in an 
> election held under plurality or runoff rules, their lack of core 
> support would prevent then from ever being opposed by just one candidate.
> 

This is a debate topic.  I like modifying my above case a bit via 29 D>B - 
all of the basically B voters like either C or D better - but those who 
like C see D as an enemy and D voters return the compliment.  In your 
words, B has no core support - BUT - MAJORITIES like A or C or D LESS!

BTW - B might do better in Plurality than in IRV - unable to vote for B 
PLUS C or D, at least some likely would vote for B.


> Here is an election scenario that demonstrates this problematic dynamic 
> in Condorcet voting.
> 
> Imagine a polarized election in which:
> Candidate A is favored by 55% of voters who all disapprove of candidate B,
> Candidate B is favored by 45% of voters who all disapprove of candidate A.
> 
> Now suppose candidate C joins the race and stresses his/her likeability 
> and avoids any controversial issues.
> 
> If 15% of the A supporters are drawn to candidate C's friendly image, 
> the result would now be:
> 
> Candidate A=40% 
> Candidate B=45% 
> Candidate C=15%.
> 
> Under plurality rules, Candidate B wins even though 55% of all voters 
> consider Candidate B the worst choice
> 

NOT fatal - voters are doing the best they can in Plurality - their 
attraction to C has impacted their liking for A..


> Both IRV and Condorcet always avoid this fatal flaw. Under IRV rules, 
> Candidate C is eliminated in the runoff count and Candidate A again wins 
> with 55%.
> 

I accept your desire - BUT  - it does not count unless you say it more 
clearly.


> Under Condorcet rules, however, if Candidate A's supporters rank 
> Candidate C above Candidate B whom they detest, and B supporters also 
> rank C second because of disdain for A, candidate C can win. Because the 
> Condorcet winner may be someone who nobody considers a particularly good 
> candidate, it punishes candidates who take clear stands on controversial 
> issues and rewards candidates who say little of substance.
> 

More clearly, please.  If you say the voters LIKE C, even IRV might agree 
as to winner.


> Theoreticians must understand that the measuring tool (the voting 
> system) can change candidate behavior and the information voters have 
> for assessing them. The logic of Condorcet promotes a campaign strategy 
> that is detrimental to political discourse and voters' ability to get 
> the information needed to assess candidates. It primarily encourages 
> avoiding alienating voters, and discourages taking stands on potentially 
> divisive issues. Over a series of Condorcet elections we believe most 
> major candidates would avoid taking clear policy stands, and in turn 
> thus likely lead to lower voter turnout and less well-informed voters.
> 

Huh!  As I said earlier, IRV and Condorcet USUALLY will agree as to 
winner, meaning that, except for IRV strategy attempts, the same arguments 
apply to both.


> IRV provides a better balance between the competing values of being 
> representative of substantial numbers of voters and of having broad 
> appeal. IRV encourages candidates to distinguish themselves and to have 
> sufficient boldness to win many first-choice rankings, but it also 
> encourages candidates to reach out to supporters of other candidates and 
> avoid vilifying them in overly negative attacks. This is a desirable 
> incentive package.
> 

Ditto.


> A voting system does not just select winners. A voting system shapes the 
> nature of political debate, and largely dictates how well informed most 
> voters are able to be. An inoffensive candidate who studiously avoids 
> taking any controversial stands, but simply campaigns by projecting an 
> image of being friendly and honest can be everybody's acceptable 
> compromise and win with Condorcet even if nobody considered him/her the 
> best candidate. While plurality voting over-values the ability to be a 
> voter's first choice, Condorcet overvalues the value of ability to avoid 
> being voters' last choice. IRV provides a compromise by giving 
> appropriate weight to both values.
> 

Ditto.


> We also believe reformers must weigh pragmatic considerations. We 
> welcome Condorcet voting advocates seeking to persuade voters and 
> elected officials to support their preferred system over plurality 
> elections and runoff elections, just as IRV advocates do. But we believe 
> that efforts to adopt IRV are far more likely to be successful. The fact 
> that Condorcet all too possibly could elect a candidate who would come 
> in dead last in a traditional American plurality or runoff election 
> essentially makes it a political non-starter - both from the perspective 
> of ordinary voters and of elected officials. In contrast, IRV has a 
> widely-accepted analog: the traditional runoff election that Americans 
> use in many elections and that most nations use around the world when 
> electing a president. The fact that many people are familiar with 
> runoffs and appreciate their logic helps IRV advocates fend off attacks 
> by opponents.  Indeed recent wins at the polls, growing support from 
> civic leaders and editorial writers and activity in half of our state 
> legislatures indicate IRV's viability.
> 
Sales pitch.  Agreed that IRV backers talk louder, and have made some 

sales.  Condorcet, more like a tournament, needs better selling.


Do think that, assuming IRV complete vote counts get published, as 
Condorcet backers can easily do, IRV will get its own embarrassment.

BTW - IRV CLAIMS a majority votes for its declared winner.  Given about 
1/3 of voters bullet voting for each of 3 candidates, there IS NO majority.
-- 
  davek at clarityconnect.com    people.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
            Do to no one what you would not want done to you.
                  If you want peace, work for justice.