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Diego Renato wrote:<br>
<blockquote type="cite">All one-round voting systems that allows ballot
truncation are
vulnerable to bullet voting, resulting the same results of plurality
voting. For instance, suppose that some voter has A as his/her first
preference. S/he can vote like this:
<br>
<br>
Approval: A: approved; B: rejected; C: rejected; D: rejected ...<br>
Range (0 - 100 scale): A: 100; B: 0; C: 0; D: 0 ...<br>
Preferential (IRV, Condorcet, etc): A>B=C=D=...<br>
</blockquote>
<br>
A voter never gets a better result for hirself in IRV by bullet voting,
because lower rankings do nothing until the voter's higher-ranked
candidates have been eliminated.<br>
IRV meets "Later-no-Harm".<br>
<br>
Also as has been pointed out, in all the methods you mention it only
takes a small proportion of voters to max. score or rank more than one
candidate to give a different<br>
result from plurality voting. I regard Approval as vastly vastly better
than Plurality (FPP) even if in practice nearly all voters bullet vote
and the result is always the same<br>
as if they all had.<br>
<br>
<blockquote type="cite">Additionally, there are several instances which
only binary input
voting systems are reasonable. Complex systems are hard to adopt in
low-educated underdeveloped countries.
<br>
</blockquote>
Yes, interesting problem.<br>
<br>
<blockquote type="cite">This system, called Improved Approval Runoff
(IAR), has the goal to resist bullet voting through simple ballots.<br>
<br>
Description:<br>
<br>
1) On the first round, the voter can vote for as many or as few
candidates as desired.
<br>
2) If some candidate has more than 50% of approvals, the most approved
is elected.<br>
3) If not, that candidate runs a second round against other candidate -
the most approved after a new count which the votes for the first one
are reweighted to 1/2.
<br>
4) The winner is the candidate who receives a majority of votes on the
second round.<br>
<br>
On computer simulations, the top-two approval runoff method selected
more times the Condorcet winner than any Condorcet method. I think that
IAR is slightly fairer than top-two approval runoff under real voters.
<br>
<br>
Any comments?</blockquote>
<br>
I think this is not bad for a simple method and a big improvement on
"top-two approval runoff", which I long ago rejected as a strategy
farce. <br>
<br>
Parties with a chance of winning a normal approval election will run
pairs of clones and ask their supporters to approve both of them.
Normal<br>
plurality top-2 runoff is more vulnerable than IRV to the Pushover
strategy, but approval top-2 runoff is much much more vulnerable again.<br>
Voters who are confidant that their favourite or one of their
favourites (with their approval) can qualify will have incentive to
also approve all the<br>
candidates they are sure that their favourite/s can beat in the
runoff. If a faction succeeds with this strategy then the final round
will be between<br>
their favourite and a candidate with much less sincere support. If
more than one faction attempts it then it is just possible that both
qualifiers will<br>
be "turkeys" with very little sincere support.<br>
<br>
<blockquote type="cite">
<p><a name="push-over"></a><b>push-over</b> <br>
The strategy of ranking a weak alternative higher than one's preferred
alternative, which may be useful in a method that violates <a
href="#monotonicity">monotonicity</a>.</p>
</blockquote>
<br>
<br>
<blockquote type="cite">2) If some candidate has more than 50% of
approvals, the most approved is elected.</blockquote>
This is understandable, but if more than one candidate has more than
50% approval then I would still like to see a runoff. Maybe I'd like
to <br>
see a runoff in some circumstances even when only one candidate has
50+% approval. This special rule of yours creates extra Compromise
incentive<br>
and also means that the result can be changed by adding or removing
ballots that ignore all the viable candidates (just by changing the
absolute size of <br>
the 50% threshold).<br>
<br>
<blockquote type="cite">3) If not, that candidate runs a second round
against other candidate -
the most approved after a new count which the votes for the first one
are reweighted to 1/2.
</blockquote>
<br>
This prevents the final from being between a pair of clones from the
same party. It makes the Pushover strategy a bit less effective because
voters<br>
can't have their first-round votes count at full strength for both
their sincere favourite and the turkey. How did you decide on the
reweighting figure<br>
of 1/2? Why not "reweight" those ballots that supported the first
qualifier to zero? That would mean that Pushover strategists would
have to take<br>
some extra risk by not approving their sincere favourite in the first
round (as in normal plurality top-2 runoff).<br>
<br>
Chris Benham<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<blockquote
cite="midab7e60980708151300q298f7550jbbc8a71899a339f5@mail.gmail.com"
type="cite">All one-round voting systems that allows ballot truncation
are vulnerable to bullet voting, resulting the same results of
plurality voting. For instance, suppose that some voter has A as
his/her first preference. S/he can vote like this:
<br>
<br>
Approval: A: approved; B: rejected; C: rejected; D: rejected ...<br>
Range (0 - 100 scale): A: 100; B: 0; C: 0; D: 0 ...<br>
Preferential (IRV, Condorcet, etc): A>B=C=D=...<br>
<br>
Additionally, there are several instances which only binary input
voting systems are reasonable. Complex systems are hard to adopt in
low-educated underdeveloped countries.
<br>
<br>
This system, called Improved Approval Runoff (IAR), has the goal to
resist bullet voting through simple ballots.<br>
<br>
Description:<br>
<br>
1) On the first round, the voter can vote for as many or as few
candidates as desired.
<br>
2) If some candidate has more than 50% of approvals, the most approved
is elected.<br>
3) If not, that candidate runs a second round against other candidate -
the most approved after a new count which the votes for the first one
are reweighted to 1/2.
<br>
4) The winner is the candidate who receives a majority of votes on the
second round.<br>
<br>
On computer simulations, the top-two approval runoff method selected
more times the Condorcet winner than any Condorcet method. I think that
IAR is slightly fairer than top-two approval runoff under real voters.
<br>
<br>
Any comments?<br>
<br>
________________________________<br>
Diego Santos<br>
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</blockquote>
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