On 9/9/05, <b class="gmail_sendername">Jobst Heitzig</b> <<a href="mailto:heitzig-j@web.de">heitzig-j@web.de</a>> wrote:<br>
<br>
<div><span class="gmail_quote"></span><div> Hm. This adds up to
102%, but I guess from what you wrote next that the first 10% are meant
to be just 8%. I will assume so here.<br>
<br>
Quite right, of course. Let me throw out a corrected example (although the strategy still works on the "102%" example):<br>
<br>
9% C>>B>A<br>
22% C>>A>B<br>
18% C>A>>B<br>
12% B>C>>A<br>
12% B>>A>C<br>
17% A>B>>C<br>
10% A>>B>C<br>
<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">> B>C 41% approval<br>I suppose this means the B>C defeat is considered to have strength 41% since this is B's approval.
<br>> C>A 61% approval<br>> A>B 45% approval<br><br>OK.
In DMC, C wins. That is, the C voters have sucessively buried B. But
the last 10% A-voters can prevent this by approving of B also. This
means that it seems wise to approve the Condorcet winner and all above
her in order to assure a good compromise, right?</blockquote><div><br>
Easy to make an example where that's not the case. Just imagine a slightly higher percentage of the CBA faction approve A:<br>
<br>
9% C>>B>A<br>
15% C>>A>B<br>
25% C>A>>B<br>
12% B>C>>A<br>
12% B>>A>C<br>
17% A>B>>C<br>
10% A>>B>C<br>
<br>
B>C 41% approval<br>
C>A 61% approval<br>
A>B 52% approval<br>
<br>
</div><div>Now at least some order-reversal is required. Or, if
you like, let's move the "approval strategy" needle for the edge
factions much farther over:<br>
<br>
5% C>>B>A<br>
5% C>>A>B<br>
39% C>A>>B<br>
12% B>C>>A<br>
12% B>>A>C<br>
25% A>B>>C<br>
2% A>>B>C<br>
<br>
B>C 49% approval<br>
C>A 61% approval<br>
A>B 66% approval<br>
<br>
Now the only viable strategy for the 25% edge faction is for at least
18% of them to insincerely rank B>>A>C. Even if they can
convince the "obstinate" 2% to join them in strategic action, their
only other option is for all 27% of them to completely order-reverse to
B>A>>C, to make B the Condorcet winner.<br>
</div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">It
is true that they can perform this, but it is false that this is the
only strategy for the A-voters to prevent the C-voters from
manipulating the election by burying. In fact, it is far more natural
for the A-voters to just approve B which effectively protects B from
losing.</blockquote><div><br>
The point was that for the one faction I was talking about, the
strategic vote involved order reversal and approval burial. The
fact that other factions were not acting strategically is ultimately
irrelevant. You could also have accused the 12% B>C>>A
faction of nonstrategic approval strategy. Again, this is not the
point. You asked for a situation where this was the optimal
strategy, and I gave you one.<br>
<br>
We could argue all day about how realistic the example is, and indeed
that is an important question. My point is simply that the
strategy applies over a much wider range of situations than it does in
winning votes (although a narrower range than margins). I would
trust Kevin's simulations to tell me how much often moreso than either
of our intuitive instincts.<br>
<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">> There
is a rather large set of situations where this can occur. I
constructed this one to be what I saw as a plausible situation where
insincere order-reversal and disapproval was clearly a superior
strategy.<br><br>Superior to just approving B as I suggest? Why do you think so?</blockquote><div><br>
Because the 17% A>B>>C voters do not have the power to coerce
the 10% A>>B>C voters to vote how they want them to.
They can try to convince them, and they will have a good argument on
their side, but they may fail. This does not change the fact that
their optimal strategy is B>>A>C. The question of what
is the optimal strategy for that faction, alone, is not
debateable. It is order-reversal and approval burial of their
favorite.<br>
<br>
I know see Kevin's response, where he stated this more succinctly.<br>
</div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">> In winning votes, the ABC faction can simply equal-rank.<br><br>So
you suggest winning votes was better since it provides for a
counterstrategy which requires *insincere* rankings. But in DMC the
counterstrategy I specifyed above involves only sincere rankings, so I
guess this rather shows that DMC is better in this situation.</blockquote><div><br>
No, the 17% in the example I showed have no incentive to vote in
a fashion other than A=B>C in winning votes. That is the
point. The strategy of one faction is at question, not the
strategy of every faction in the electorate.<br>
<br>
Same election in winning votes:<br>
<br>
9% C>B>A<br>
40% C>A>B<br>
12% B>C>A<br>
12% B>A>C<br>
27% A>B>C<br>
<br>
B>C 51%<br>
C>A 61%<br>
A>B 67%<br>
<br>
Now, if at least 17% of the A>B>C voters (that same 17% from
before, of course) vote A=B>C, B wins. This is of course a
less extreme strategy than B>A>C (or B>>A>C).<br>
</div></div>