[EM] Proposed bullet-voting prohibition criterion

[Kristofer Munsterhjelm]

On 01/27/2013 03:45 PM, Peter Gustafsson wrote:
>
> There are lots of voting system criteria that have been described,
> but I have not seen this one - or any one like it - described
> before.
>
> Bullet-voting prohibition Criterion: "A voting system should not be
> constructed in such a way so that it is both legal and rational for a
> voter to fill in a ballot with only one party or candidate name, so
> that the voter refuses to order by preference all candidates that are
> not his first preference."

This criterion seems to be two combined. These are:

- It should not be possible to submit a ballot listing only one party 
("legal")
- For any ballot that includes only one party, there should exist at 
least one other ballot that lists more than one party and which doesn't 
make the voter worse off if he were to vote that ballot instead 
("rational").

I think the second here is pretty much Later-no-harm, though I share 
Benham's opinion regarding methods that only pass LNHarm or LNHelp (and 
not both or neither). That is, a method that passes only LNHarm 
encourages random-fill (the voter adding more parties or candidates in a 
random order because it can't hurt), and a method that passes only 
LNHelp encourages bullet-voting.

As for the first criterion, that's reasonable enough, but I think the 
intent can be thwarted.

> Since FPTP enforces bullet voting, it obviously fails the BVP
> criterion. In Approval voting, it is legal to vote for only one
> candidate, so it fails also. In score voting, it is legal to give 99
> points to one candidate and 0 points to all others, so it also fails.
> All other voting systems (that I can think of right now) can be made
> compatible with this proposed BVP criterion by adding a rule that the
> voter must supply at least 4 (or whatever number sufficiently high)
> most preferred candidates, otherwise the vote is spoiled.

It's easy to modify Approval and Range/score to pass the "legal" part of 
the criterion, though. Just say that the Approval ballot is only valid 
if at least two candidates are approved, or that the Range ballot is 
only valid if, after removing a candidate given max score, there are 
candidates with non-min score left.

> So, what would happen if a voting system with a BVP-criterion
> enforcement would be introduced? I see two possible scenarios:
>
> 1. The big parties split into several very similar parties, so that
> hidebound voters of that party can vote a complete list of only party
> members.
 > 2. The big parties do not split, and the voters of those
> parties engage in mutual burying. Their voters vote their party #1,
> then supply a long list of minor parties, so that they do not have to
> give any help to the hated other big party. Meanwhile, many 3rd party
> voters will vote one big party at the bottom, and several will
> tactically vote both big parties at #1 and #2 from the bottom.

There's a third possibility. The parties may produce "decoy lists" that 
aren't expected to get much support at all and are thus easily 
controlled by the parent parties. Party voters could then vote for a 
party and a randomly picked decoy list to get around the BVP limitation.

For instance, say that party X introduces 12 pseudoparties (one for each 
month) and instructs their voters to vote for X and the pseudoparty 
corresponding to the voter's birth month. Then, in a majoritarian 
system, the pseudoparties won't get their candidates elected (because 
the parent party will always have significantly more support); and in a 
proportional representation system, the method would give seats to the 
parent parties and these parties' voters would be considered represented 
by them, thus again giving the pseudoparties few seats.