[EM] Majority winner set

[Bart Ingles]

Markus Schulze wrote:
> Suppose that this given voter would have approved Nader and disapproved
> Gore and Bush if he had no information about the voting behaviour of
> the other voters. Then I am saying that this voter votes insincerely
> when he approves Nader and Gore and disapproves only Bush after he
> has got additional information about the voting behaviour of the
> other voters. You seem to consider it to be an advantage of Approval
> Voting that he can't express both preferences. I consider it to be a
> disadvantage of Approval Voting that he can't express both preferences.

>From my own perspective as a voter, I consider it an advantage NOT to be
able to express all preferences.  Here's why:

If I can express all preferences, then I must assume that other voters
can do likewise.  Now typically, I will consider some preferences to be
more important than others.  By being able to express all preferences,
all I am really gaining is the right to express preferences I consider
unimportant, in addition to the important ones.  In exchange for this
slight gain, I must accept that other voters' slight preferences can
cancel out my important ones.

By restricting the ability to express preferences, you encourage voters
to focus on the distinctions they consider important, leaving less
important ones for other voters to decide (who may be more interested in
these).  This closely mirrors the social contract we call common
courtesy, where individuals willingly accept a slight inconvenience when
it provides a greater benefit to another -- such as holding a door open
for someone carrying an armload of packages.  The expectation is that
we, or someone we care about, will benefit from this social contract at
some time or another.  Immediate reciprocity is not nessary or expected.

> 
> The fact that he can't express both preferences means that he can
> influence the election result only when he has very exact information
> about the voting behaviour of the other voters. When his information

I think you know better than this.  The behavior of approval voting in
the complete absence of polling information is well known.  Its
average-case performance w/resp. to individual expectations is nearly as
good as the Condorcet methods, and certainly better than IRV. 
Approval's worst-case behavior is actually better than Condorcet's, at
least where excluding extremely unpopular candidates is concerned.


> isn't exact enough then he will probably approve all potential winners
> resp. disapprove all potential winners so that his vote has no influence
> on the election result.

I don't know what you mean by this statement, but your conclusion makes
no sense.

Bart



> 
> Is this really what you want?
> That a person who doesn't have exact information about the voting
> behaviour of the other voters should not be able to influence the
> result of the elections?
> 
> Markus Schulze