On 27.11.2011, at 8.05, matt welland wrote:
> On Sat, 2011-11-26 at 22:31 -0500, robert bristow-johnson wrote:
>> On 11/26/11 6:58 PM, matt welland wrote:
>
>>> Also, do folks generally see approval as better than or worse than IRV?
>> they don't know anything about Approval (or Score or Borda or Bucklin or
>> Condorcet) despite some effort by me to illustrate it regarding the
>> state senate race in our county.
>
> I wasn't clear. I want to hear opinions from the list: Is approval
> better or worse than IRV and why?
Unlike others, I think Approval might be worse.
Lets assume that there are two wings, left and right. Left has slight majority
this time. Left consists of multiple candidates or multiple parties. Right has
one candidate.
One basic problem of Approval is that all left supporters have to approve all
plausible winners of the left wing in order to guarantee that left will win.
That makes Approval quite numb to the opinions of the voters. If (almost) all
approve all, the choice among left wing candidates will be random. Some voters
might be tempted to approve only their favourites, and make them win this way.
They may well succeed. But if number of strategic voters grows, then right
wins. This kind of close competitions are not rare in politics. And in such
situations one can not tell which candidate is the strongest among the left
wing candidates (and a natural choice that all left supporters should approve).
All candidates present themselves as likely winners, and their supporters tend
to think that their favourite candidate is the strongest one.
Approval is nice because the ballots are simple. It works fine with two major
parties and some new third parties. But when the third parties grow, the
problems arise. There are no good solutions and no good guidance to the left
voters in the situation where left wing has two or more plausible winners.
If one of the left wing candidates is a Condorcet winner (closer to the centre
than the competing candidate), then that candidate may propose that all
supporters of the other candidate should approve him although his supporters
need not approve that other candidate. Maybe there are some voters that would
even rank the right candidate second. But often there is no such clear order.
And the other left candidate might be slightly ahead in first preferences.
IRV has its problems too. The reason why it might be better than Approval is
that voters still have some sensible strategies, like ability to compromise. In
the environment above left wing IRV voters will anyway rank all left wing
candidates first. One of them will win, although the best of them might be
eliminated too early. If there are two equally strong left candidates, the
number of first preferences will decide which one of the left candidates will
win. That is not as bad as the problems of Approval in this situation.
In IRV minor parties are a bigger problem than in Approval. In this example
they may steal first preference votes from the second favourite of their
supporters, and thereby make some worse left wing candidate win. In this
situation the voters may compromise. If their own candidate has no chances to
win, they might be ok with ranking the stronger second favourite above him. Not
good, but at least the voters can do something. And even if they will do
nothing, they would still get a left winner.
If there is a clear Condorcet winner (like in Burlington), IRV will have
problems. So will Approval. But this mail is already too long, so I'll stop
here.
My basic argument against Approval is that although IRV may make wrong
decisions, it does not lead to as terrible situations as Approval does (with
more than two plausible winners). In Approval the idea of all left wing voters
approving all the left wing candidates sounds quite impossible. Therefore it is
likely to violate the opinion of the majority. And the voters do not have any
good strategies to fix the problem. Approving all the left wing candidates and
letting a random one of them win, or to allow others (maybe the few strategic
voters) to decide, does not sound like a system that voters would like to keep.
In IRV people are (as we have seen) quite ignorant and don't understand that
someone else than the ("fair") IRV winner should have won. The results are a
bit random, but often people just think "better luck next time". So,
"impossible situations" vs. "randomish elimination process".
Juho
----
Election-Methods mailing list - see http://electorama.com/em for list info
