[EM] Winning-votes intuitive?

[Blake Cretney]

Adam Tarr wrote:

>Blake wrote:
>
>>Because if you just judge by the votes you give, without any 
>>preconceptions about what Bush voters would really prefer, I think it
>>is obvious that Bush really does deserve to win in your example.
>>
>My assumption, which seems reasonable given the left-right spectrum 
>that most voters are comfortable placing themselves on, is that nearly 
>all Bush voters would prefer Gore to Nader.  If it pleases you, we can 
>include this stipulation as part of my example.
>
That's all I meant to say.  The fact that the Bush voters actually 
prefer Gore is part of the example and is the reason you think Gore 
should win.

>>But as for the strategy argument, my response is as follows.  Let's 
>>imagine that some voters aren't aware that they are allowed to vote a 
>>partial ranking.  Then, they will have to randomly rank candidates 
>>instead of placing them as equal.  On average, these random votes will 
>>tend to cancel each other out, with an effect as if they had voted in 
>>margins.  So in margins, knowing that they are allowed to vote partial 
>>rankings doesn't give a new opportunity for strategy that did not
>>exist before.
>>
>
>This is true... would-be truncators voting randomly will have the same 
>effect as Ranked Pairs would predict otherwise.  But is this a good 
>rationale for using Ranked Pairs?  The idea that one can truncate is 
>not even remotely hard to grasp.  It's no harder than the idea you can 
>only vote for one candidate in plurality.  Very few real-world voters 
>will mistakenly fill out full preferences.
>
Are you claiming that it is always, or generally, a bad idea to give a 
complete ranking in RP.  I believe that to be false.  If you don't have 
any particular strategic knowledge, you should give a full ranking. 
 Certain strategic knowledge can make it rational to order-reverse. 
 Sometimes in these situations you can get away with truncation instead 
of order-reversal, although this is more likely to fail.

>Now, I think you're driving at a more subtle point here, that 
>truncation actually makes a strategic difference in SSD, and blunting 
>that difference makes the voting strategies simpler.  My counter to 
>this is that truncation also has a strategic impact in Ranked Pairs, as 
>my example (with the attendant assumption about the true preference of 
>the Bush voters) shows.  It's true that the Bush voters could achieve 
>the same effect by ranking their ballots randomly after Bush, but the 
>coordination required to pull that off is dramatically harder to 
>achieve.  For all practical purposes, truncation has a strategic impact 
>in both methods.
>
How can voting randomly require co-ordination?  BTW, sophisticated Bush 
voters should actually place Nader ahead of Gore in your example.

>>However, if you count ballots in a way that tends to penalize those
>>who vote partial rankings, which SSD does, 
>>
>
>I still haven't seen the example that shows this.  I don't doubt that 
>one exists, although I do doubt that the example will seem as likely as 
>the one I provided.  I could be wrong of course.
>
Your example shows this.  The Bush voters were penalized because they 
voted partial rankings instead of completing their ballots randomly. 
 Your example stipulates that this is desirable because the 
incompleteness is strategic.  But the method has no way of knowing 
people's true preference, so the same effect occurs when the voters are 
sincere.

>>the voters would actually be better off believing that they aren't
>>allowed to vote partial rankings, since this will cause them to
>>randomly rank, and thereby avoid the penalty.  In fact, an argument
>>can be made that this is true even counting with margins, but the
>>effect is minimized.
>>
>I've shown an example here where truncation produced a BENEFIT, not a 
>penalty, with margins.
>
No benefit over filling out the ballot randomly, which you can do even 
if incomplete rankings are banned.

>Furthermore, why shouldn't their be, in certain cases, some penalty to 
>truncation?  It basically means you're displaying less preferences -- 
>you're voting less.  It seems very natural that this could hurt you on 
>occasion.  The idea that more fully expressing your preferences can 
>hurt you bothers me a lot more.
>
If you don't express a preference you have, it is natural that this 
should hurt you as the method can't take that preference into account. 
 But that's not what we are talking about here.  The point is that if my 
first choice is A, the method penalizes me for not choosing between B 
and C, by strengthening one or both candidates, and therefore weakening A.

In both SSD and Ranked Pairs, a strong pairwise loss tends to hurt a 
candidate much more that a victory helps.  So, you want to encourage 
strong losses/victories between candidates at the end of your ballot. 
 This is how SSD penalizes truncators (and in fact anyone who votes a 
partial ranking).  When you vote a partial ranking you miss the 
opportunity to increase the victories between the candidates at the end 
of your ballot.

>>So, if people are better off believing that ranked ballots are not 
>>allowed, why not just ban partial rankings?  I mean, rather than allow 
>>partial rankings, but covertly penalize them, why not just be up front 
>>about it and say they aren't allowed? 
>>
>
>Well, if you force full ranking, then almost all the differences 
>between Ranked Pairs and SSD dissolve.  ALL the differences between 
>Plain Condorcet and Ranked Pairs dissolve.  So making this argument 
>sort of defeats the purpose of arguing between Ranked Pairs and SSD in 
>the first place.
>
My point exactly.  I don't agree that truncation is that much of a 
problem, so I am willing to allow incomplete rankings.  But if you 
disagree, I think that Ranked Pairs with full rankings is a better 
choice than SSD with partial rankings allowed.

>That said, I think that as a matter of voter freedom, we should not 
>force the voter to fully rank the candidates.  This makes voting far 
>more of a chore in a place where a bunch of fringe candidates that the 
>voter has not studied (nor does he/she care to study) make the ballot.  
>This could make voting a very frustrating experience for many people.  
>An election reform proposal that forces full ranking would also be hard 
>to sell to the public.
>
If I participated in an SSD election, I would feel it necessary to rank 
all candidates at the end of my ballot, even if I had to vote randomly 
to do it.  I would advise others to do the same, and I believe I would 
be giving good advice.

>
>Finally, this could create some ugly strategies in a real election.  In 
>my example, for instance, the Republicans would want to ask their 
>supporters to either vote random second places, or some other scheme 
>designed to produce an even split.  This hardly seems democratic, and 
>the public reaction would be very negative.
>
Or even worse, they might encourage order reversal, which is a better 
strategy.  I consider it much more of a threat than truncation.

>>Is it because you're hoping to 
>>fool people who are trying to use strategy themselves?
>>
>
>I'm not sure I follow this suggestion.  There is strategic value to 
>truncation in Ranked Pairs, and possibly SSD.  You're going to have to 
>explain to me the scenario where some people try to strategically 
>truncate in SSD, only to be burned for it.
>
Isn't that the point of your example?  The Bush voters, not 
understanding SSD, strategically truncate and are thwarted as a result. 
 But if they had understood the method, they would have placed Nader 
over Gore, or at least voted randomly between them.  SSD only has a 
benefit if voters do not understand it.

---
Blake Cretney