On Mar 17, 2008, at 19:49 , Greg Dennis wrote:
Excellent points, Juho. I'll just add a few more.
- You're right, Nader supporters could learn that it's in their best
interest to give Gore a '10'. Under plurality, they could also learn
that it's in their best interest to vote for Gore instead of Nader.
Although they could learn the best strategy in both cases, some will
not, and even of those that do, many will choose to vote their true
preferences anyway. The desire to vote one's "true conscious" cannot
be ignored.
Yes, and Range is often even advertised so that good voters are
recommended to mark their sincere opinions on the ballot.
- Voting the "correct" strategy relies on good polling data prior to
the election to know how the candidates are likely to fair. Putting
aside the inaccuracies we've seen in recent polling, polling is
virtually non-existent in local and state legislature races throughout
the country.
Range and Approval typically assume the presence of some good poll
data or other good guesses. They can also be used without such
information but then the nature of the election changes somewhat
(towards sincerity). In this case nobody should however have any good
information available since that would put some voters in better
position than others. In a typical political environment this doesn't
work very well since typically people have at least some good guesses
on who could be popular.
In political elections Range and Approval are thus based on the
assumption that voters will not vote according to their sincere
(unmodified) preferences but are expected to find out their best
strategy and then vote accordingly. Other methods like Condocet and
IRV are closer to allowing voters to reach good results also with
sincere/unmodified ballots.
In Range and Approval the poll information typically helps voters to
identify the two main candidates and then put an Approval cutoff
between these two. The Obama-Clinton-McCain example and the problems
of Range (and Approval) there could be generalized so that typically
there are problems with those methods when the number of potential
winners rises from two to three.
Juho
- Requiring a strategy and knowledge of current polling data to vote
"correctly" will inevitably disenfranchise lower-information, probably
poorer, voters who lack the time to do that research in advance.
I don't believe that Range Voting will eliminate even the kind of
spoilers that IRV does away with.
Range sure has some weaknesses.
Consider two-candidate race between
Bush and Gore in which 51 voters prefer Gore to Bush and 49 prefer
Bush to Gore. Following the directions given on the RangeVoting.org
website, voters should give a '10' to their favorite candidate and a
'0' to their least favorite:
51 people rate Gore=10, Bush=0
49 people rate Bush=10, Gore=0
the result: Gore=510 > Bush=490 (Gore wins)
Now we re-run the election with Nader in the race. When Nader
enters,
5 people for whom Gore was their first choice switch to preferring
Nader. Those 5 voters rate Nader a '10' and push Gore down to '5':
46 people rate Gore=10, Bush=0, Nader=0
49 people rate Bush=10, Gore=0, Nader=0
5 people rate Nader=10, Gore=5, Bush=0
result: Bush=490 > Gore=485 > Nader=50 (Bush wins)
One basic rule is that the best strategy for Range voters is to vote
roughly in Approval style (=only 0 and 10 used). Your example is a
valid concern on Range behaviour and it is quite possible that under
some circumstances the method could pick a bad winner. The Nader
supporters could however learn that their best strategy is to
vote in
Approval style Nader=10, Gore=10, Bush=0. This would keep Range
still
working (if all the voters can follow this Approval strategy
recommendation).
Range may however fall again when the support of Nader grows. Or we
could talk about the current Obama-Clinton-McCain case where the
approximate first place support of these candidates is 25%-25%-50%.
In this situation especially the Obama and Clinton supporters are in
trouble since voting Obama=10, Clinton=10, McCain=0 (as above in the
Nader example) would mean that they don't take any position at
all on
the Obama vs. Clinton question. Range thus is in trouble when there
are two critical questions to answer (Democrat vs. Republican, and
Obama vs. Clinton).
(The Nader case was easier since the voters could maybe quite safely
assume that Nader will not win in any case. In the latter case there
were three potential winners.)
Juho
How could the 5 Nader voters suddenly have a different utility for
Gore? In reality, the rating a voter will give to a candidate isn't
some fixed objective measurement of their happiness with a
candidate,
but a rating relative to the options available. In short, everyone
will naturally grades on a curve. To say that RV satisfies IIA is to
ignore the reality that ratings will inevitably be relative.
Thus, Nader would still be labeled a spoiler, because his entrance
into a race causes some to rate Gore lower.
Agree?
Greg
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