Talk:Arrow's impossibility theorem
My removal of the electionmethods.org link
In the edit summary, Psephomancy added a link to an archived version of something posted on electionmethods.org:
...with the summary:
- did you just remove it because it's a dead link?
Well, it was mainly that. The author (Russ Paielli) pulled the website down. It seems to me that we're not doing readers of this wiki much of service by offering an unannotated link to an archive of a webpage from 2005.
I agree with much of what that particular web page says. At some point, I'd like to perform a plagiarism-free restatement of some of the important arguments made on that page, rather than redirecting people to an old archived snapshot of a long defunct website. I think there was plenty of discussion about IIAC on the EM list when this page was first published. If I recall correctly, there was an essay or two on the old electionmethods.org that I contributed some prose to, but I can't remember which ones, and it might even be this essay. I'd have to dig up the very old email backups to find what I wrote.
In general, I've always been careful not to dismiss Arrow's result as irrelevant to my preferred method. As we've seen with w:Gibbard's theorem, the core principle of Arrow's theorem (i.e. there is no "perfect" voting system because many important criteria are mutually exclusive) holds true no matter the system. If I recall correctly, some of Russ's restatement of my writing implied I was dismissive of Arrow, and I didn't want to be associated with a dubious effort to declare Arrow's theorem irrelevant.
So thanks for digging up the archive link to that page. A little bit of annotation around that link would be wonderful. Hopefully an active Electowiki editor can perform the plagiarism-free restatement I was hoping for. -- RobLa (talk) 05:04, 8 January 2020 (UTC)
EPOV on Arrow and cardinal methods
Just a bit ago, I posted a message to the EM list about Arrow's theorem and cardinal methods. I'll quote a little bit of the message here:
Many Score voting[1] activists claim that cardinal methods somehow dodge Arrow's theorem. It seems to me that *all* voting systems (not a mere subset) are subject to some form of impossibility problem. Arrow's impossibility theorem deserved great acclaim for subjecting all mainstream voting systems of the 1950s to mathematical rigor, and it's clear that his 1950 paper and 1951 book profoundly influenced economics and game theory for the better. His 1972 Nobel prize was well deserved. It seems that it has become fashionable to find loopholes in Arrow's original formulation and declare the loopholes important. Even if the loopholes exist, talking up those loopholes doesn't seem compelling, given the subsequent work by other theorists broaden the scope beyond Arrow's version.
I expand on these points quite a bit in my email. The full message is archived here: "(EM) Arrow's theorem and cardinal voting systems". I'm eager to read what the membership there thinks on this topic, since that group of people has frequently been successful at changing my mind on a particular topic. I'm also eager to read your response to my message (privately or publicly, via whatever mode of communication you prefer). -- RobLa (talk) 23:47, 9 January 2020 (UTC)
- I would not say you are wrong but there are a few things you are missing. Most importantly is that Gibbard-Satterthwaite theorem is not Arrows theorem. Yes they are related but Gibbard-Satterthwaite is way more general. Arrows theorem talks about the specific criteria which will be failed. The importance of arrows theorem is that it shows that Ordinal systems must have one of the bad issues. Gibbard-Satterthwaite shows that all systems has some issue with strategy but it may not be a particularly bad issue. I realize that it is tempting to say all systems have issues but I think that is a misguided narrative because it implies that all issues are equally bad. All systems have trade-offs and some of the trade-offs are not worth it. The question is about what is the optimal balance. Most use Arrow as a way to say that Ordinal systems will not be monotonic and monotonicity is too important to trade away when cardinal systems exist. The narrative "Who cares if IRV is nonmonotonic? Arrows theorem shows that all systems will be nonmonotonic" is pushed by FairVote. It is wrong. Monotonicity is a core concept to fair voting. --Dr. Edmonds (talk) 00:26, 10 January 2020 (UTC)
- Dr. Edmonds, I think we agree on many things. For example, monotonicity is an important (and underrated) criterion for electoral systems. Furthermore, all systems have trade-offs, and some of the trade-offs are not worth it (we agree on that, too). But, I believe all rhetorical strategies also have trade-offs, and some are not worth it. Trying to jump through a loophole in Arrow's theorem just complicates the discussion in an unhelpful way. The EM list discussion in January (that stretched into February) didn't come to a consensus, but generally was sympathetic to my original January 9 email. I particularly appreciated Forest Simmons' response on January 13, where he improves on my "no perfect car" metaphor. Even if cardinal methods are not subject to Arrow's theorem, there are plenty of other theorems that close the loophole described. If you still hold this position, could you make your case on EM list? -- RobLa (talk) 22:56, 16 March 2020 (UTC)
- If I may, I'd like to point out that one of the main reasons imo that it is interesting to say cardinal methods aren't affected by Arrow's Theorem is because this implies cardinal methods pass IIA. That is an argument some cardinal advocates make in favor of their methods (that this implies their voting methods are free of the spoiler effect, since candidates can enter and drop out of the race without changing the result). While that can be vigorously debated (for example, if any voter changes their scores for candidates who are present both before and after some candidates enter or drop out of the race, then cardinal methods fail IIA), it seems only right to put something on this wiki that helps the debate to happen. BetterVotingAdvocacy (talk) 23:22, 16 March 2020 (UTC)
- RobLa I just can't get behind your argument. You admit that cardinal methods are not subject to Arrow's theorem. Your argument seems to be that since they are subject to other similar theorems we should say that it is subject to Arrow's. That is totally illogical. We need to be precise in what applies to what. I do not understand your motivation for wanting to do this. --Dr. Edmonds (talk) 03:07, 17 March 2020 (UTC)
Finding EPOV on Arrow
- This is a continuation of "EPOV on Arrow and cardinal methods"
Dr. Edmonds, could you do me a favor? Could you do one of the following:
- a. find someone that agrees with you in the January 2020 list of respondents to my "Arrow's theorem and cardinal voting systems" email, and let me know which person I need to provide a better response to?
- b. join the EM list, and state your objection to my January email on that list?
- c. propose some other off-wiki mechanism to convince me that your position isn't controversial?
- d. just concede that we need to agree to disagree, and that because I disagree with your point of view (and many smart people on EM list seem to agree with me), the idea that "Arrow doesn't apply to cardinal methods" is controversial (e.g. I believe it does, you believe it doesn't)
I'm willing to concede that I may be wrong. But the membership of EM list wasn't able to convince me I'm wrong, and believe me: they have a lot of practice telling me that I'm wrong, and some of them have been doing it for 24 years. It's a tough crowd. I might be willing to change venues, but given the robust response I received in January, I feel pretty confident saying "the EM list has spoken", and I don't see the value of trying to overrule the discussion by forum shopping.
I'm already willing to concede that I'm not going to convince you that I'm correct. I'm asking that we agree to disagree, and consider the EPOV to be "Some people believe Arrow doesn't apply to cardinal methods" rather than flat out insisting that "Arrow doesn't apply to cardinal methods".
Could you choose one of the options above? Thanks! -- RobLa (talk) 04:00, 17 March 2020 (UTC)
- I am not going to read that forum. It is too hard to follow the flow to get any information out. It seems all you want is proof that Arrow's theorem does not apply to cardinal methods. I will choose your option C. How about a quote from arrow saying exactly that?
Now there’s another possible way of thinking about it, which is not included in my theorem … [E]ach voter does not just give a ranking. But says, this is good. And this is not good. Or this is very good. And this is bad. So I have three or four classes … This changes the nature of voting.
- That quote is taken from here. Read section 5.3 and 5.4 for the details. They get into some of the extensions and how people have tried to build a cardinal version of Arrows theorem. At this point there are two possibilities you could have to resist this. 1) You dispute what Stanford and Arrow himself are saying. If this is the case then we will have to agree to disagree. 2) You admit that Arrow's actual theorem does not cover cardinal systems but know cardinal systems are covers by OTHER theorems. You want to call all theorems "Arrows theorem" so as to hide the fact that Ordinal systems are more flawed than cardinal systems. If this is the case then you have a clear biased and malicious intent. --Dr. Edmonds (talk) 20:59, 17 March 2020 (UTC)
- Dr. Edmonds, quick point: STAR is covered by Arrow's Theorem. This is because it satisfies the majority criterion in the two-candidate case and thus fails IIA. So I recommend creating some terminology to cover only Approval and Score (and I think Majority Judgement also?) to ensure people don't get misled into thinking all cardinal methods are not covered by Arrow's Theorem. BetterVotingAdvocacy (talk) 18:29, 18 March 2020 (UTC)