Discussion about this post

User's avatar
Robert Bristow-Johnson's avatar

Okay, Ned, thank you for writing this. Specifically:

"The ballot in an Instant Bracket Voting election could look the same as ballots in any Ranked-Choice Voting election. The voters would rank the candidates in order of preference, ..."

We must make it clear that, in this case, this *is* a form of Ranked-Choice Voting and not allow FairVote to appropriate the umbrella term to mean only Instant-Runoff Voting. Personally, I think that's the *only* way Instant Bracket Voting can be done. Expecting voters who never ever think about March Madness or athletic tournaments to fill out brackets on their ballot is not going to fly. Not in my opinion. It has to be a ranked-ballot, RCV. (But not IRV.)

But then the question I have is this: We know that this is Condorcet-consistent, so we know that no matter how it's seeded, if there is a Condorcet winner (which is 99% of the time) that Condorcet winner will be elected. But if there is *no* Condorcet winner, the outcome of the election will depend on how the first round is seeded. That's a problem. The method should be deterministic and not depend at all on a random manner of who gets matched up with whom.

That's why I think that Round Robin (or what I might call "straight-ahead Condorcet") is fairer and clearer than Instant Bracket Voting. And if there *is* a cycle, it's not exactly a tie unless the votes were perfectly symmetrical between the candidates involved in the cycle (the Smith set).

Consider a Round-Robin Tournament that ends up lacking a Condorcet winner. If it were hockey or basketball or wrestling, they could do as Nic Tideman suggests and favor the matches with scores having wider margins over the matches with smaller margins as a basis for identifying the champion. Or Minimax.

Two years ago, I was able to get a Vermont legislator and counsel to write a Condorcet RCV bill and we were considering Bottom Two Runoff IRV vs. a straight-ahead Condorcet (with Plurality for the contingency that there is no Condorcet winner). https://legislature.vermont.gov/Documents/2024/Docs/BILLS/H-0424/H-0424%20As%20Introduced.pdf

The BTR-IRV was attractive because it is the smallest modification to Hare IRV that makes IRV Condorcet-consistent and the modification is easily understood, It's also a Single-method Condorcet system. It just does what it does and someone is elected. If there is a Condorcet winner, that candidate will be elected. If there isn't, someone is still elected with this single method.

The reason we settled on a Two-method Condorcet system was because this legislator, the legislative counsel, and I all agreed that "The law should say what it means and mean what it says."

It seemed that straight-ahead Round Robin, with language to meaningfully resolve a cycle, would be easiest for everyone to understand and to buy into it. If there ever was a cycle, most people would accept the resolution of the cycle as fair. If I were to do it again (and we might do it again this session, I dunno), I think it would be Condorcet-TTR for top-two runoff instead of Condorcet-Plurality. That would make it elect the Hare IRV winner in the case of a cycle involving just the top three candidates.

But I'm a little nervous about this Instant Bracket Voting if there is a Condorcet cycle and the outcome depends on how the candidates are seeded. It shouldn't.

Expand full comment
p48h93h438's avatar

https://arxiv.org/abs/2101.03455

RSEB has some strategy-resistance properties, too (though I don't claim to understand them)

Expand full comment
19 more comments...

No posts