[EM] Expressing pairwise preferences

[Juho Laatu]

Hello Dave et al,

On Aug 13, 2005, at 06:16, Dave Ketchum wrote:

> I __do__ get to express my n x (n-1) / 2 pairwise preferences (part or 
> all, as I as a voter choose).  I just am forced to be consistent.  If 
> I vote A>B and B>Z, then I have voted A>Z.  If there is a C for which 
> I have given no explicit specification, then my above partial vote 
> implies A>C, B>C, and Z>C.

Few observations about the ability to express the n x (n-1) / 2 
preferences:

1) It would be quite easy to remove the rule of considering unranked 
candidates to be ranked last. This could of course lead to unwanted 
results like the most unknown and uninteresting candidate winning the 
election. For this reason it is good that by default unranked(/unknown) 
candidates are considered to be less preferred than the ranked ones. In 
principle it would be ok to allow those voters that know what they are 
doing to express their opinions also more widely, e.g. a>b>c[cut] 
(which means that unlisted candidates are not ranked last) or 2) 
a>b>others>c. The latter option introduces the risk of people ranking 
widely the strongest competitors of their favourite candidate last, 
even though that normally doesn't do them much good (would e.g. lead to 
election of some unknown candidate in the case of three major 
candidates).

3) It would be also possible to allow circular rankings like a>b>c>a 
(mentioning "a" twice means that the intention is to describe a loop). 
Consistent voters do not normally have such looped opinions I guess, 
but they could be used for strategic or counter strategic reasons. (I 
don't however want to encourage this kind of voting since I think that 
voting methods that use strategies and counter strategies extensively 
are most probably not good enough to be used in normal public elections 
anyway.)

4) One option would be to allow candidates to be grouped. This could be 
useful if the number of candidates is large. One could vote for example 
Bush>Gore>Reagan>Republicans>Democrats>Greens ("Republicans" will be 
interpreted here as "other Republican candidates than Bush and Reagan" 
etc.).

Allowing individual Republican candidates to be ranked below the 
generic "Republicans" item could be banned even if such use of group 
entries would be allowed otherwise. This is to avoid the negative 
effects discussed in case 2. It may be better to force voters to list 
all republican candidates if they want to place one of them last. In 
this way they are at least forced to see what kind of (maybe even less 
wanted and totally unknown) candidates they are ranking above the 
candidate they want to rank last, and probability of "unintended stupid 
votes" would probably decrease.

5) Yet another way of voting would be to use fragmented votes. One 
could vote Bush>Reagan;Gore>Clinton, which means that Bush is preferred 
to Reagan and Gore is preferred to Clinton but the voter has not 
indicated anything about if (s)he prefers Bush to Gore or the other way 
around, Bush to Clinton etc. I think voters that would be interested in 
voting this way would still be quite consistent. It is quite ok to have 
an opinion "Bush is nicer than Reagan but I don't care if Republicans 
or Democrats will win (others may decide)".

The current (EM) default rules concerning ranking based ballots are 
simple, in most cases they offer voters all the tools they need, and 
they often stop voters making foolish things (like ranking their worst 
enemies last or electing some unknown candidates). It could be possible 
to allow e.g. some or all of the five special cases above to be used 
but I doubt if they would bring more benefits than they do bring 
problems in the form of making the system more complex and inviting 
voters to do something stupid. Case 4 could maybe be helpful if the 
number of candidates is large. I have also sometimes had feelings like 
the example in case 5 myself. Note that combination of cases 5 and 1 
makes it possible to set separately any of the n x (n-1) / 2 pairwise 
preferences.

Best Regards,
Juho