[EM] reply to Juho Laatu on range voting

[Warren Smith]

>Juho Laatu:
Here's my quick characterization [of range voting]:
- RV is a wonderful method for dominantly non-competitive elections  
and polls
- RV utility function is very good when compared to most alternative  
methods
- RV is very vulnerable to strategic voting
- but strategic voting is indeed simple, just vote as in Approval
- also the FAVS properties of RV make it a nice and understandable  
tool for the voters
- in competitive situations where most voters vote in Approval style  
RV may still elect the Condorcet winner with quite good probability  
(but only with probability)

RV is certainly one of my favourite methods for seeking answer to  
question which one of the clouds on the sky is the prettiest  
(assuming that we want an exact result and are not afraid of doing  
some calculations while lying on the grass). But when we move to  
competitive elections in a traditional (typically competitive)  
democratic society RV is not my first choice ... reasons:
- RV does not support the idea of "one man one vote" very well (well,  
in theory yes, but...)
=> strategic (Approval style ballot) voters may gain multiple times  
the weight of a sincere (Range style ballot) voter
=> radical voters ("the competing candidate is all bad") voters may  
have multiple times the weight of a moderate ("the competing  
candidate is not quite as good") voter
- if RV becomes in practice Approval, then the RV side is a trap for  
voters (that are competitive but) who don't know that their vote is  
more effective in Approval style
- RV "rewards" individual voters that vote strategically by giving  
them more power
- strategic voting is beneficial in practically all situations (not  
just in extreme cases and/or requiring detailed information and/or  
coordination and/or having risks of failing and/or causing damage  
instead of benefit to the voter)

In highly competitive situations one could use Approval (RV 0..1)  
instead of normal RV (=when one doesn't want to recommend the voters  
to use Range style). But if one does so, then one could also consider  
using Condorcet or other corresponding methods that have been  
designed to cope in competitive environments (like Approval does) but  
that are more expressive than Approval. 

--REPLY by Warren D Smith:
First:
A theorem ( http://rangevoting.org/AppCW.html )
indicates that range and approval voting both return the honest-voter Condorcet
winner if all voters act strategically.  Basically, if we are not in
the "prettiest cloud" but rather in the "I love/hate Nixon" emotional mode,
then we vote max or min on Nixon.  Assuming all voters do that with
their threshold placed somewhere between the two candidates they judge as most likely to win,
(which they do because they are not strategic idiots)
and assuming one of these two happens to be the honest-voter Condorcet winner, then
theorem: Range & Approval both will elect the honest-voter Condorcet winner, but meanwhile
Condorcet methods often will fail to do so.  [Juho Laatu claims misleadingly
that "RV may still elect the Condorcet winner with quite good probability  
(but only with probability)."  Actually, under these assumptions, the probability is 1.
Further, Condorcet methods with strategic voters will elect the honest-CW with
merely a probability strictly below 1.]

Second:
The claim that "honest" Range Voters can have their votes 
outweighed by large factors by strategic ones, is correct.  However, 
(1) at least their honest 
vote will never actually work against them (e.g. compared to not voting at all) and 
(2) their honest statement "X is my favorite" in their vote, will never hurt them.
With every Condorcet method, by theorem, both of those properties are false.

Anyhow such outweighing
(a) does not matter if strategic and honest voters have the same political distributions,
(b) is entirely their own fault and hence is self-correcting over time and not a
valid attack on the voting system.

To see what I mean by (b) consider a Range Voting election.  Nixon loses.
The pro-Nixon voters complain:  "we foolishly did not indicate a high preference
for Nixon over Kennedy. But Kennedy Voters said they had high preference the other way.
So Nixon lost."   The response to this complaint:
"It is your own fault idiots.  This is not the fault of the voting system."
Any court would throw this "complaint" out, and argue that Kennedy SHOULD have won.
It is rather like a bank complaining it was "robbed" after throwing handfuls of
dollars into the streets and then those dollars were unexpectedly not returned
by the pedestrians.

In contrast, consider a Condorcet election.  Gore loses to Bush thanks to a Nader spoiler
effect.  The Nader voters complain "the voting system penalized us for honestly ordering
Nader top, Gore second. If we had had range voting we could have expressed our
honest ordering, without being penalized."
That in contrast, seems genuinely the fault of the voting system and not of the voters.

Warren D ?Smith
http://rangevoting.org