[EM] truncation in IRV example (as requested by Benham)

[Warren Smith]

example of situation in IRV where truncating a ballot
is strategically desirable:

If your favorite is F but F is eliminated in round 1,
and the rest of your ballot is a "no show paradox" example
in which you are better off "not showing up to vote",
then truncating your ballot
  F --the rest truncated---
is strategically superior to voting
  F honest-ranking-of-others.

So it is merely a matter of producing no-show-paradox examples
for IRV (or any other such voting system).  Many are known...

Explicit example From an old EM post by me (note 2) and
[SJ Brams: Voting procedures, ch. 30 pp.1050-1090 in
vol 2 Handbook of Game theory, ed. R.Aumann and S.Hart,
Elsevier Science, NY 1992]

 A>B>C>D  7 votes
 B>A>C>D  6
 C>B>A>D  5
 D>C>B>A  3
IRV ==> A wins.  (Elim order: D, B, C.)
1. This is despite fact B is Condorcet winner, i.e. would win direct
pairwise elections versus every opponent!
2. If the 3 voters in the last row instead had
ranked D first - but refused to say more, i.e. refused to provide
their 2nd 3rd 4th choices -
then B would have won (which those voters prefer over A).
This illustrates the fact that in IRV, voters can be motivated to
refuse to rank-order some of the candidates, thus defeating IRV's purpose
of garnering ordering information from the voters.
3. And: if these 3 voters instead had dishonestly voted
A>D>C>B  then B would have won (which they'd prefer to A)
despite fact they just RAISED their opinion of A to
first place and nothing else changed! That is
an example of "non-monotonicity".

wds