[EM] PR-STV with approval based elimination

[James Gilmour]

Raph Frank  > Sent: Thursday, April 30, 2009 6:33 PM
> Also, I think later no harm basically means "won't 
> compromise".  I am not sure that it is even a desirable 
> criterion for a method to have and think that the fact that a 
> method that doesn't meet later no harm is a not major issue.

 I don't think support for Later No Harm means "won't compromise".  If you impose a social choice interpretation on the rankings on
a ballot, you would probably consider LNH to be "undesirable", but of course, the rankings on an STV ballot are not social choice
scores and should not be interpreted in that way.

One problem with abandoning LNH is that it opens the way for strategic voting, that is, when a voter ranks the candidates in some
order other than the sincere 'first to last' order of preference because the voter knows that some feature of the voting system will
enhance the changes of the real high preferences being elected if the rankings marked on the ballot are distorted in a particular
way.

It is my experience when explaining voting systems to ordinary electors that they do consider LNH to be important.  They not want a
voting system in which marking their second choice would count against the election of their first choice.  And of course, STV
ensures that that cannot happen.

James Gilmour

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