[EM] Why Condorcet

[Juho]

On Jul 7, 2010, at 6:31 AM, robert bristow-johnson wrote:

> On Jul 6, 2010, at 9:31 PM, Dave Ketchum wrote:
>
>> Ballots:  Must support write-ins and, perhaps, 3 ranks (do not need  
>> to rank rejects and can do equal ranking).
>
> i think that the number of ranking levels should be as large as the  
> number of candidates (and there should be ballot access laws that  
> make it difficult enough to get on the ballot that no more than  
> maybe 5 candidates normally get on).

Yes, having sufficient number of ranks is important. With limited  
number of ranks the method might quite easily not elect the sincere  
Condorcet winner.

If there are too many candidates so that it is too tedious to rank  
them all or the ballot sheet would be too large, then one could  
satisfy with some smaller number of ranks. It is important that all  
the voters will rank all the possible winners. It is not as important  
to rank all those candidates that have no chances to win (we will lose  
some important/interesting information but this does not change the  
winner). The number of ranks should be however higher than the number  
of candidates that can possibly win since there must be space for  
ranking also those sincere favourites that have no chances to win. It  
is not easy to estimate how many extra ranks there should be. Maybe  
some party has 100 minor candidates and the voters want to rank all of  
them above the strong candidates of the other parties (just to show  
their sincere opinion). Or alternatively one could give them advice  
that they should not rank too many of them, and that they should never  
truncate any possible winners. In the latter case few extra slots  
could be enough. The choice depends at least on the available space,  
interest of voters to rank numerous candidates, number of candidates,  
number of candidates per party, number of possible winners.

My point is thus that although the ability to rank all the candidates  
is important, sometimes you could do also with smaller number of  
ranks, and that using less ranks than there are possible winners could  
lead to bad results / bad performance with sincere votes / worse than  
best winners. Truncation of possible winners is always a risk (=best  
candidate maybe not elected).

Juho