[EM] Optional Later-no-harm AER
chrisbenham at bigpond.com
Sun Dec 21 11:40:01 PST 2003
An idea for improving Approval Elimination Runoff (an
Approval-STV hybrid) :
1: Voters rank the candidates and also place an Approval cutoff.
Truncation allowed, and if equal preferences are allowed
then the votes are split. Default placement of the cutoff can be
either below first preference or below lowest ranked
2: A candidate with a majority of first preferences is elected. If no
candidate has a majority, then eliminate the candidate
with the fewest approvals and transfer preferences IRV-style.
Whenever a candidate is the highest ranked of those
remaining candidates on a majority of the ballots that distinguish
between them; then that candidate is elected.
3: If, after one or more eliminations, there are ballots that no longer
make any approval distinction between the remaining
candidates, then those ballots that approve none of the remaining
candidates shall be counted as approving the highest-ranked
of them and those ballots that approve all of them will be counted as
approving all but the lowest-ranked.
This last feature is my new idea. Ranking but not approving a candidate
can never harm an approved candidate, so voters
can have as much Later-no-harm as they want.
Without this feature, AER and other methods that use an approval
cutoff give too big an advantage to well-informed
strategic voters. My idea is that as and when a voter's approval cutoff
in it's original position becomes redundant/useless
(because it no longer distinguishes between the remaining candidates),
it is moved the minimum distance neccessary for
this to be not the case.
Some people who are not Condorcet fans have been down on the idea of a
"low utility" CW with very few first preferences
winning. They can be reassured that with this method such a candidate
cannot win unless they are explicitly "approved" by
a significant proportion of the voters.
This method can easily be adapted to elect more than one winner by PR.
It doesn't meet the Condorcet Criterion, but that is incompatible with
A while ago (Sat.Apr.13,2002) Adam Tarr posted something on
In his example, these were the sincere preferences:
100 voters. Gore is the sincere CW.
With approval cutoffs, this was his problematic scenario:
"Now, Bush wins the approval runoff 55-51-33. This is where ACC's favorite
betrayal scenario comes in. Since Bush wins the approval vote, the only
way the majority can guarantee a Gore win is to make Gore the initial
Condorcet winner, which requires that the Nader camp vote Gore in first place:"
My point is that this is no problem for AER. Nader is easily eliminated and then Gore
(the sincere CW) wins.
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