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Kevin,<br>
You wrote (Sun.Jun.6):<br>
<blockquote type="cite">
<pre>Mutual Majority and Clone Independence are easy to meet, but they also don't
guarantee much. Clones, and a majority-strength coalition for a set of more
than one candidate, hardly ever exist. I would love to see a real IRV election
where they did.</pre>
</blockquote>
Where did you get that idea? It happens all the time in Australia. The Federal
government here is based on two conservative<br>
parties in coalition, which are permanent allies. In some seats they each
field a candidate, and in those seats they tightly "exchange<br>
preferences". In some of those seats one of them wins with the help of the
second preferences of the other, and so together they<br>
make a "majority strength coalition". Decades ago, there was a small right-wing
Catholic (Democratic Labour Party) party that kept the Coalition in power
by always giving them their second preferences, and I assume the favour was
returned. In those seats where the big conservative party won with DLP preferences,
I suppose that was another "majority strength coalition". In fact I believe
that IRV<br>
was first introduced so the originally trade-union based Labor Party, which
was disciplined and fielded one candidate per seat, wouldn't<br>
beat a larger number of conservative candidates, who presumably in some
seats were a majority strength anti-Labor Party coalition.<br>
<br>
<br>
<blockquote type="cite">
<pre>This is a tired scenario, but consider this while thinking of "half-clones":
40 A
35 C>B
25 B
I call {BC} a half-clone set. In Approval the C>B voters can vote CB and still get
B to win, and this doesn't involve any insincerity. In IRV those voters should put
C below B in order to avoid electing A. Not only does IRV encourage insincere
voting here, but the fact that it does so will be a strong incentive for C not to
enter the race at all.
So the biggest reason I prefer Approval to IRV is IRV's nomination disincentives.</pre>
</blockquote>
I find it a bit implausible that the C voters all give their second -preferences
to B, with no recipricocity at all. If A, B, and C<br>
were the endorsed candidates of rival establised political parties for a
seat in Parliament in Australia , then it would never occur<br>
to C to not run. The same would apply to the parliaments of many other countries,
if they were to use IRV (like the UK, New Zealand<br>
and France, and other European countries.)<br>
<br>
<blockquote type="cite">
<pre>><i> I like methods that have no zero- information strategy,
</i>
I think you are saying Approval has strategy, even with zero-info, because sincere
voting is undefined for Approval.
><i> and doesn't
</i>><i> reward indecisive voters by giving them extra clout. If voter A
</i>><i> ranks candidate X last, and because of prejudice, ignorance and
</i>><i> stupidity has no ranking of the other candidates; and voter B ranks
</i>><i> candidate Y last but also strictly ranks all the other candidates; then
</i>><i> both candidates X and Y should have the same probabilty of being
</i>><i> elected.
</i>
I still think "probability of being elected" is undefined here. Usually that
term is used when there is a tie...</pre>
</blockquote>
By "probabilty of being elected", I meant exactly that. To make it clearer,
instead of referring to two individual voters, I could<br>
instead have said that there are two equal-sized factions of voters. <br>
<blockquote type="cite">
<pre>><i> "No Zero-Information Strategy" also implies that Later-no-harm and
</i>><i> Later-no-help should be in balance. That is, that the chances of
</i>><i> harming or helping an already ranked candidate by ranking another below,
</i>><i> should be the same.
</i>
1. Can you tell me a method besides Approval which fails "no zero-info strategy"?
Because I take it you really mean that zero-info strategy should be equivalent to
a sincere vote.
2. Can you tell me a method which fails "no zero-info strategy" where LNHarm and
LNHelp are not in balance?</pre>
</blockquote>
Yes and Yes. A method that simply asks the voters to rank the candidates,
but gives voters who do anything else (based on their<br>
ratings) a better expectation, fails "No Zero-Info Strategy". I gather from
posts in the archives, that Condorcet (Winning Votes) fails<br>
because if voters have a sufficiently large gap in their ratings, say between
second and third place, they do better to insincerely rank<br>
the candidates above the gap in equal-first place. Also, it is true, or has
been strongly conjectured, that voters who do not have a sincere<br>
full ranking do better to strictly rank all the candidates below first-place
.<br>
Bucklin, Weighted Median Approval, the Woodall methods Quota-Limited Trickle-Down
and Descending Acquiescing Coalitions all <br>
fail Later-no-harm , but meet Later-no-help. That means that truncation
is a big implicit approval-cutoff, and if voters have a big gap<br>
in their ratings they would do better to insincerely not rank the candidates
below it.<br>
On the other hand, the Woodall set-intersection method Descending Solid
Coalitions meets Later-no-harm but fails Later-no-help.<br>
That means that the voter definitely does better to "random-fill", ie if
the voter does not have a full ranking, s/he should strictly rank<br>
all the bottom candidates at random.<br>
<blockquote type="cite">
<pre>><i> And of course voters who succeed in ignoring this circus and instead just concentrate on the
</i>><i> policies and qualities of the candidates, will potentially be greatly disadvantaged (much more
</i>><i> than a "naive", sincere IRV voter).
</i>
Here I completely disagree. A gut-sentiment Approval voter will probably not be far off
from his optimal way of voting. He screws up only if he approves or disapproves both of
the strongest candidates. In IRV he can screw up by not guessing who needed his traveling
vote when.</pre>
</blockquote>
I don't see why the it is particularly unlikely that the "zero-information"
(poll-ignoring) voter wouldn't distinguish between the two<br>
leading candidates (not approving either or approving both). In my opinion,
the concientious voter shouldn't have to do anything<br>
except calmly and rationally rank the candidates.<br>
<br>
Chris Benham<br>
<br>
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