At 10:37 PM 5/12/2010, Jameson Quinn wrote:
Look. It's a scenario. It's not totally implausible. We are blowing hot air if we argue too much about how plausible it is.
No, I showed some aspects of the scenario that were highly implausible as supposed "sincere" ratings. First, what was implausible was apparent discontinuity in the political spectrum, so that any voter who preferred one of the two centrists had no preference for the extremists. That indicated three basic groupings, with a large gap between them. Real voters are not distributed like that, when an election is large-scale.
The second problem was a problem, but not so implausible. Each of the two extremist groups were almost evenly divided on which of the two centrist candidates was preferred. Yet they all had a preference. The centrists were shown as equal-ranking the left and right candidates, equal bottom.
That indicates, from the centrist view, that the left and right are far away from them. The only way we identify this as a centrist party is the uniformity of left in ranking them above right, and right in ranking them above left.
A system that deals with it well is better than a system which doesn't, all other things being equal. All other things are never equal, so it's just one factor among many.
I'm not sure what "it" is, that's my point. From the preferences, there is no clear winner that is intrinsic. It seems that the best winner, though, would be one of the centrists, because a centrist is everyone's first or second choice. The question devolves, then, on which of the two centrists is the best choice. If they totally bullet vote, high partisan feeling is implied between them. Thus they are centrists only by relation to the other two parties. That's odd in itself.
There is really only one clear problem shown by the scenario. If the centrists bullet vote -- which would be very odd, since neither one of them is a frontrunner -- one of the extremists could win. If it's a top two runoff (FPTP primary), the runoff could be the two extremists. That's a known (and real) flaw of TTR with sincere voting in the primary. But that flaw seems highly unlikely to surface in Bucklin, where everyone gets to express their sincere first preference and then add approvals queued for voting in the second or third round. The centrists, given their equal bottom rating for the left and right, would very much dislike seeing the election go to the extremists, so pure bullet voting seems very, very unlikely. And since left and right get no support from anyone else, but will clearly support a center candidate over the other extreme, one or the other centrist will likely get a majority (or both), and I showed the range of votes consistent with the setup. If it were top-two runoff, the most-feared outcome for the centrists would be for neither centrist to make it to the runoff, so pure bullet voting becomes very, very unlikely.
I am planning to one day make a program which explores how likely and how severe strategic opportunities are in each system. Typifying such strategic opportunities is useful prior work.
You could tweak Warren's simulator, IEVS is it called? It was designed to be heavily configurable. What "strategic opportunity" was there in this election that is not depending upon high knowledge? The election setup is extremely close. Left and right are in balance. The center candidates are close to each other, and every move toward bullet voting risks a very bad outcome.
A "strategic opportunity" is not one where it is merely *possible* that it improves the outcome, truly, but where it will *likely* improve the outcome. In order to use such an opportunity, one must know that the election can be moved in a desired direction without risking a larger loss.
Here is my analysis: Given any election method that is remotely practical, there can exist an electorate that is divided such that a voter can cast a deciding vote, if the voter votes last and has full knowledge of how others voted. In practice, this could be a very good knowledge of how others would vote, and this "final" vote could merely be reasonably likely as a deciding vote.
What the voter needs to know is where the near-tie is, and assuming that this is a two-way tie, three-way ties being extraordinarily rare, the voter then can cast an effective vote to improve utility. Is this a sincere vote?
Suppose that to cause the desired outcome, the voter must vote a full vote for the better of the two, and a zero vote for the other (if it's Range or Approval). If the voter does have another preferred candidate, then, the voter must rate the other preferred candidate equally. A Bucklin system does ordinarily allow casting a sincere vote, because Bucklin, if needed, converts a partial vote to a full vote, if it is above approval cutoff. However, if the situation is that the vote must be cast in first rank, or the less preferred candidate will win, so you can easily construct a scenario where a Bucklin voter must equal-rank or fail to exert strategic voting power.
Range doesn't do this as pure Range. IRV will do it, if there are sufficient ranks, because the favorite will be eliminated if other than one of the top two, but IRV seriously breaks down in other ways (remember, this is full-knowledge, whereas voters don't have that kind of knowledge, they have something much vaguer). Approval does it, because only full votes are allowed, but sacrifices the important expression of the favorite as such, and if there is a significant preference there, this is a form of strategic voting. Condorcet methods will do it, because all that is needed is for that pairwise preference to be sincerely expressed (and these are intrinsically full-vote comparisons).
"Strategic voting" in Range is meaningless unless it means equal ranking when there is a preference. There is never any preference reversal However, Range as a ballot form for Bucklin does allow ranking but equal voting power, for sets of candidates (one set per rating).
This is the paradox of the "strategic" analysis of Approval Voting: it is often asserted that a voter "really" approves of both A and B but only votes for one of them for "selfish" strategic gain. However, if there is a gain, that must mean that the voter *really* has a preference, so, *of course* the voter will vote to elect one over the other! The reverse is sometimes asserted, that Approval fails the majority criterion because a voter may approve of more than one candidate while, supposedly, preferring one to another.
Basically, fans of preferential voting, when Brams published his paper claiming that Approval Voting was "strategy-free," meaning that preference reversal was never an advantage, redefined strategic voting to include equal ranking in the presence of a preference, and, at the same time, to assert that there was some absolute quality of candidates called "approval," and that therefore bullet voting when a voter "really" approves of more than one candidate was "strategic."
If we step back and look at democratic traditions in peer organizations, we'll see that repeated ballot is a method of seeking majority approval; if it's vote-for-one, the adjustments take place outside of the ballot process, as candidates withdraw and voters shift their votes. Approval voting allows this to collapse, but the first round would normally start with voters voting for their favorites. If a Range ballot were used for the first round, with explicit approval cutoff, the voters can more efficiently adjust their votes, understanding what compromises are more likely to fly. Bucklin simulates this, quite well, actually. Make it two-round, and the simulation becomes even closer, with a deliberative stage (the runoff process including new campaigning).
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