[EM] Best Single-Winner Method

C.Benham cbenham at adam.com.au
Tue May 21 22:45:20 PDT 2019


Can you please explain, perhaps with an example, how your "Instant 
Pairwise Elimination"
method can possibly "elect a non-Condorcet winner"?

As I understand it, the method eliminates all the non-members of the 
Smith set, and then if
more than one candidate remains, next eliminates the candidate who 
(among remaining candidates)
is lowest ranked on the highest number of ballots, and then repeats both 
steps until one candidate

Is that right?

 From the page you linked to:

> To appreciate how easy it is to understand, here’s a full description 
> of the IPE method:
> “*Voters rank the candidates using as many ranking levels as there are 
> candidates, or at least 5 ranking levels if ovals are marked on a 
> paper ballot and space is limited and lots of the candidates are 
> unlikely to win. During counting, each elimination round eliminates 
> the candidate who loses every pairwise contest against every other 
> remaining candidate. If an elimination round has no pairwise-losing 
> candidate then, for that round, each ballot gives one count to the 
> lowest-ranked remaining candidate on that ballot, and the candidate 
> with the highest such count is eliminated. The last remaining 
> candidate wins.*”

Chris Benham

On 22/05/2019 5:13 am, VoteFair wrote:
> On 5/20/2019 12:46 PM, steve bosworth wrote:
>> Re: Best Single- Winner Method
>> ...
>> Firstly, please correct me if I am mistaken but currently I am assuming
>> that  we all would ideally want the Best Single-Winner Method:
>>  1. To be simple enough so voters  can both use it and understand how it
>>     is counted;
>>  2. To minimize the wasting of citizens’ votes (see below),  and
>>  3. To guarantee that the winner among 3 or more candidates is the
>>     candidate most supported by at least 50% plus one (an absolute
>>     majority) of all the citizens voting, and
>>  4. To offer as few incentives and possibilities for voting tactical.
> I suggest that Instant Pairwise Elimination provides a great balance 
> among these requirements.
> 1: It's simple to use, and simple to understand how to count.
> 2: Rarely could a voter identify a situation where their vote was wasted.
> 3: It's not a Condorcet method, yet it would be very rare for it to 
> elect a non-Condorcet winner.
> 4: Tactical voting is possible, but only when a rock-paper-scissors 
> cycle is involved AND involves the most popular candidates.
> As a reminder of Instant Pairwise Elimination, it's described here:
> https://democracychronicles.org/instant-pairwise-elimination/
> Richard Fobes
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