[EM] Why I think IRV isn't a serious alternative 2

Abd ul-Rahman Lomax abd at lomaxdesign.com
Tue Dec 16 16:32:22 PST 2008

At 09:58 PM 12/15/2008, Kevin Venzke wrote:
Kevin's post had lost all formatting, the quoted 
material was extremely difficult to follow, and 
the new text was only distinguishable with 
difficulty, because I recognize, sort of, my own 
writing. So I may have missed a lot....

>Hi, --- En date de : Dim 14.12.08, Abd 
>ul-Rahman Lomax <abd at lomaxdesign.com> a écrit :

>>Remember, not all voters will 
>>follow >frontrunner strategy. They don't with 
>>Plurality, why should they start with Approval?

>Well, I'm not using "frontrunner strategy" but 
>"better than expectation" strategy, since that can be applied more universally.

"Frontrunner strategy" is a common one that seems 
to help with ranked methods as well as Range 
ones. Make sure you cast a maximally effective 
vote for a frontrunner, and, where "against" 
matters, against the worst one. Usually there are 
only two frontrunners, so it's easy. 
"Expectation" is actually tricky if one doesn't 
have knowledge of the electorate's general 
response to the present election situation. How 
do you determine "expectation." Mean utility of 
the candidates is totally naive and non-optimal. 
It's not how I'd vote, but, then again, I 
strongly want to see majority requirements, which 
makes bullet voting much safer.

But it's a complex issue. My point is that 
"better than expectation" has been taken to mean 
"average of the candidates," which is poor 
strategy, any wonder that it comes up with mediocre results?

>  If D voters are more resilient then it's 
> possible that B will sink instead. It's not as 
> likely to be C, though, since C has an avenue 
> of bouncing back that B and D lack. In this 
> simulation, I don't simulate voters who don't 
> care if their vote isn't expected to be effective.

Sure. To my knowledge, nobody has. But if you 
generate random utilities, then, you are missing 
something: voters with below a certain level of 
preference strength won't put any effort into 
voting. They won't show up for a special election 
like a runoff or a primary that isn't scheduled 
with the general election. Some of them will 
bullet vote, if they have a distinguishable 
preference, but it doesn't mean much, they won't 
exercise themselves for strategy, since it is all 
the same to them, more or less.

I have in mind, remember, Saari's preposterous 
example, where 9,999 voters approve the middle 
candidate ("mediocre") because this one is at or 
above the average of their favorite and the 
worst. And then comes one "nutty voter" who votes 
reversed preference, and Mr. Mediocre wins. Of 
course, what if the "nutty voter" hadn't come 
along? Mr. Mediocre might still have won, if 
there was a tiebreaker method. Totally silly 
example. People just won't vote that way.

The hard part is encouraging people to add 
additional Approvals, if they prefer a 
frontrunner, or just if they have a significant 
preference for one. And it's not clear that we 
should even try! Not in a first round, anyway. 
Bucklin is nice because it puts up a small fence, 
to protect a first preference, but not to prevent 
compromise in the second round, etc. In Bucklin, 
do you think that a majority of voters would add 
a mediocre second choice as an additional 
approval in the first round? Hardly! So *theory* 
might show Bucklin as not satisfying the Majority 
Criterion if we allow additional approvals in the 
first rank, but that's totally unrealistic in 
public elections. People will bullet vote, lots 
of them. FairVote claims almost 90% did in 
Bucklin elections used for political primaries in 
the U.S (What they don't say is that IRV likewise showed heavy truncation.)

The facility of additional votes helps supporters 
of minor candidates, it gives them a choice that 
they didn't have under Plurality. But most voters 
don't need it and most won't use it. Fixing the 
spoiler effect, generally, takes only a few 
percent of voters using additional ranks or 
approvals. (This is entirely separate from the 
illusory help provided by IRV, in fabricating a 
majority by discarding exhausted ballots.)

>>To summarize this, the scenario makes sense 
>>only if B, C, and D are in a near-tie. If both 
>>B voters and D voters prefer C over the other 
>>of B and D, then C is, indeed, their compromise 
>>candidate! It's perfectly rational that the B 
>>and D voters, iterating over polls, increase 
>>their support for C, but it will never go all the way.

>  Well it wouldn't be both the B and D factions. 
> You would only add votes for C if you believe 
> your expectation is dropping. That happens when 
> your preferred candidate (D) looks to be 
> slipping. The B voters have no need to 
> compromise that far. In this situation, D 
> voters who decline to vote in the main contest 
> are basically "voting for Nader."

That's right, and it is their right, and that 
many voters do this prevents the "mediocre 
candidate" scenario from happening. And if a 
majority is required, it's all safer. Want to 
vote for Nader alone in the primary? Fine. If 
enough people do that, there will be majority 
failure and there will be a runoff. Slightly 
improved chance that Nader is in that runoff! 
I.e., the polls or whatever other expectations 
existed were wrong. He wasn't a "minor 
candidate," he was a frontrunner, in fact.

Approval and similar methods simply allow voters 
to make a *reasonably safe* move toward some 
compromise. IRV "protects" them from helping an 
opponent of their favorite, but, at the same 
time, protects other candidates such that the 
favorite might be prevented from winning. IRV 
proponents emphasize the protection, but 
certainly not the loss of opportunity. In 
reality, the question doesn't arise for most 
voters. Would Nader voters have been worried, in 
2000, that their vote for a frontrunner, say 
Gore, might have "helped Gore to beat Nader"? I don't think so.

As to those who prefer a frontrunner, they are 
highly unlikely to add an additional Approval for 
another frontrunner. Voting for Gore *and* Bush? What? Why bother?

>> > The behavior described seems reasonable, 
>> proper, and is > effective for finding a 
>> compromise winner. Is there some > problem with it?

>No, I don't think so. It's pretty good behavior 
>actually. At least on its face, it would seem 
>that Approval would ruthlessly favor the median 
>voter's candidate in this kind of scenario.

Well, probably. That's the most likely candidate 
to be the best compromise, to attain a majority. 
(If plurality Approval is adequate, all methods are more dangerous!)

>The big concern is what happens when poll stability can't be achieved.

Nah! Most voters won't pay that much attention to 
polls, they will just vote their gut. Polls will 
be used by those who are very seriously involved, 
who want to maximize the power of their vote. I 
think most of the "big concern" is simply 
imagination. There won't be big surprises with Approval. Little ones, sure.

A poll would have to be *way* off to seriously 
impact my Approval Vote in a majority-required 
system. In plurality Approval, strategy based on 
polls would loom larger. Sure, it could 
oscillate. But how large would the osciallations 
be? And, in the end, the winner is the candidate 
accepted by the most voters. It's not going to be 
a terrible result, if Approval falls flat on its 
face, it elects a mediocre candidate because the 
voters didn't get the strategy right.

But working against this is the natural tendency 
to bullet vote, which should prevent that 
outcome.... and which might increase the need for 
a runoff, but a runoff between, say, top two 
approved candidates, should fix the "mediocre" 
problem. (I prefer, you know, using a full Range 
ballot and preference analysis, to detect 
Condorcet failure and provide a means for the 
majority (or at least a plurality!) to fix it.

>>Bucklin allows them to maintain their sincere 
>>preference, but, effectively, vote this way. 
>>Some might add C in the second rank, some in 
>>the third, depending on their preference 
>>strength. But some will always bullet vote, 
>>perhaps even most. Real voters don't give up so easily as your simulated ones!

>I did simulate MCA, and yes, the D voters 
>continued to vote for D as their favorite (they 
>were not allowed to list multiple favorites, but 
>this was simply to make the coding more 
>manageable). I don't know what you mean by 
>voters not giving up so easily as my simulated 
>ones. How easy is easy? I could conceivably 
>program some voters to insist on being sincere. 
>(In whatever sense that it is not sincere to 
>vote also for C.) But it seems to me that this 
>type of voter is a bad thing for Approval, just 
>as it is under Plurality. Kevin 
>Venzke       ---- Election-Methods mailing list 
>- see http://electorama.com/em for list info

What type of voter is bad for Approval? Easy compromiser or tough bullet voter?

(Multiple favorites isn't terribly important in 
Bucklin, but it's a way of handling overvotes: 
interpret them! And if there are two candidates 
and I have trouble deciding which I prefer, they 
are both "favorite," allowing equal ranking makes 
the voter easier -- and more accurate as well, 
more true to actual preferences.)


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