[Election-Methods] MCA's IIB problem fixed
chrisjbenham at optusnet.com.au
Mon Jan 28 13:19:37 PST 2008
I just realised that my suggested IIB-fix of MCA does cost a criterion
Later-no-Help. Adding middle-ratings can help top-rated candidates by
increasing the Max Pairwise Opposition of their rivals.
I consider having LNHelp and LNHarm in (at least probabilistic)
balance to be more
desirable than either by itself, so I don't mind losing MCA's
LNHelp (since it badly
fails LNHarm). But I have to withdraw my suggestion that MCA doesn't
have (for a
3-slot method) a maximal set of properties.
And I think there are better 3-slot FBC-complying, LNHelp failing
methods that use
MPO information combined with ratings information (than my suggested
One possibility: "If any candidates have a top-ratings score not
smaller than their MPO
score, disqualify the other candidates. Elect the undisqualified
candidate with the highest
Approval minus MPO score".
Kevin Venzke wrote:
>--- Kevin Venzke <KVenzke at markjamesassociates.com> a écrit :
>>Kevin Venzke wrote:
>>As far as my strategy simulation is concerned, this rule change raises
>>question of how voters should evaluate the possibility that they elevate
>>candidate to the top spot on first preferences only to see him lose due
>>I don't fully understand this point. Any candidate who would win in the
>>first round of regular MCA would
>>also win in the first round of my suggested version, and in both the FPW
>> can win in the second round.
>>The only difference is that my version is more likely to have a
>>first-round winner, which I suppose in the
>>FBC-complying 3-slot ballot version might be a bit self-defeating. In
>>your FPP-approval ballot version
>>I don't see how it greatly complicates the strategy.
>Currently the value of a first-preference vote for A is estimated as the
>likelihood that A can achieve majority times the likelihood that no
>candidate will achieve majority (e.g. if a majority is guaranteed then no
>vote is of value) times the difference between A's utility and your
>expectation should the election be resolved on approval.
>With your rule you no longer simply break ties between one candidate's
>majority and "no majority"; you have to compare against each other
>candidate FPP-style. And you can't simply compare the candidate's utility
>to the approval expectation, because the candidate could lose despite
>coming in first.
>If I were implementing this method I would probably have voters keep track
>of their expectation when each candidate is the TRW but has too high
>pairwise opposition. This kind of approach so far has produced a lot of
>intelligent behavior. It has a couple of downsides though: 1. Voters can't
>predict the value of situations which weren't observed to occur in the
>polls, and thus won't try to create them, and 2. There seem to be a number
>of "cum hoc ergo propter hoc" mistakes where voters vote for situations
>that have coincided with outcomes they liked, but which didn't necessarily
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