[EM] Mike: order reversal incentive in approval?

[Bart Ingles]

James Green-Armytage wrote:

> 	This is new to me. Under what conditions/assumptions does approval have
> an order reversal incentive? Can you give an example where order reversal
> achieves something that cannot be achieved equally well without order
> reversal? 

It's sometimes called skip voting.

Something close to the following was in "Approval Voting" by Brams and 
Fishburn:

There are four candidates, and the voters are in two groups:
Group I:  a=b>c=d
Group II: c=d>a=b

If the two groups differ in size by more than one vote, an additional 
voter cannot determine which group wins.  If this voter's preference 
order is a>b>c>d he should vote only for a and c.  In other words, the 
voter has incentive to reverse his preference order for b and c (never 
for a or d).