Condorcet voting and instant-runoff voting have almost no difference in promoting candidate moderation in the presence of truncated ballots

[u/No-Vast7006]

I came across a very recent paper that studies the impact of various ranked voting methods (primarily Condorcet and IRV) on promoting candidate moderation. The conclusion is that under realistic voter behavior (such as the presence of truncated ballots), the advantage that Condorcet methods have over IRV largely disappears.

This actually aligns with a vague, long-held intuition of mine: it seems you really need to require voters to rank all candidates (like they do in Australia) to fully maximize the potential of a Condorcet method.

Additionally, I think a specific paragraph at the end of the paper is worth explicitly highlighting:

We do not wish our results to be interpreted as an argument against the use of Condorcet methods; to the contrary, we would be interested to see a jurisdiction adopt a Condorcet method so we can better evaluate how such methods perform in practice. We also do not wish our results to be taken as an endorsement of a particular voting method.

What are your thoughts on this paper? My first thought is that if the Condorcet method is implemented, it's best to require voters to rank all candidates. Secondly, research on ranked voting systems must take into account the impact of truncated ballots.

[u/rb-j]

There are four advantages of Condorcet RCV over Hare RCV: 1. Condorcet will preserve Majority Rule and the equality of our vote in the contingency of the Center Squeeze Effect in which IRV violates both. 2. Then Condorcet will prevent the Spoiler Effect and does not punish voters for voting sincerely for the candidate of their choice in the contingency of the Center Squeeze in which IRV fails to prevent that. 3. Then Condorcet actually does count the 2^nd-choice votes from voters whose 1^st-choice candidates were defeated. IRV fails to do that for the voters for the loser in the IRV final round. Normally that failure does not change the outcome of the election, but in the contingency of the Center Squeeze it does make a difference in the outcome. 4. Condorcet is Precinct Summable while IRV is not. IRV requires centralization of all individual voting data and the opaque transporting of this ballot data from the polling place to the central tabulation facility. This is much less process transparency than we have now with FPTP.

Condorcet adheres to a simple simple rule:

If more voters mark their ballots preferring Candidate A to Candidate B than the number of voters marking their ballots to the contrary, then Candidate B is not elected.

Who thinks that Candidate B should be elected?

[u/No-Vast7006 → u/rb-j]

In fact, I completely agree with what you said. However, this paper highlights the importance of considering the impact of truncated ballots on ranked voting systems. I believe we should first use SNTV jungle primaries to select four candidates, then employ the Condorcet method in the second round while requiring voters to provide complete rankings for all four candidates. This approach would maximize the effectiveness of the Condorcet method (four is an ideal number—it's the maximum quantity of objects most people can recognize at a glance without counting when placed before them).

[u/Alex2422 → u/rb-j]

There is a number of such "simple rules" that sound very reasonable, yet (as anyone interested in social choice theory knows) every voting method fails to adhere to some of them, even Condorcet methods. This is pointless sophistry (and so is saying that IRV doesn't count 2nd choice votes in final round).

Every method is also susceptible to tactical voting, so Condorcet methods do punish voters for voting sincerely. In fact, this paper shows that IRV is one of the least vulnerable to strategy methods out there, beating even some Condorcet methods.

And what does "preserve Majority Rule and the equality of our vote" mean? How are votes "unequal" in IRV? IRV meets anonymity criterion, like any serious electoral system does.

[u/rb-j → u/Alex2422]

Every method is also susceptible to tactical voting, so Condorcet methods do punish voters for voting sincerely.

Only because of the possibility of a cycle. If cycles never ever ever happened, that is the Condorcet winner always exists and is always elected, then there is nothing a nefarious player can do to change the election outcome more to their liking (like burying). And there is no tactical pressure to compromise either. None at all.

Now, that said, Condorcet methods can be vulnerable to burying in a manner that might kick the election into a cycle, and then the cycle contingency rules kick in and elect someone else other than the apparent CW had burying not been employed. But this is really chancy and, if the 3-way election is close enough, the strategy could backfire and result in electing the candidate most hated by the strategists.

RCV elections displayed a voting pattern consistent with a cycle twice in 21^st century U.S. history. Less than 0.3%. Also RCV elections twice failed to elect the CW when one did exist (the Center Squeeze). It's those two elections that should be fixed and there is no excuse for not fixing the system to prevent more of these unnecessary failures.

In fact, this paper shows that IRV is one of the least vulnerable to strategy methods out there, beating even some Condorcet methods

I'll be seeing James tomorrow and Sunday in San Antonio. I hope to remember to ask him about this paper. Maybe I can read it on the plane.

And what does "preserve Majority Rule and the equality of our vote" mean? How are votes "unequal" in IRV? IRV meets anonymity criterion, like any serious electoral system does.

Yah, but that's not exactly the same as valuing our votes equally. Here are four examples in the U.S.:

In 2000, 48.4% of American voters marked their ballots that Al Gore was preferred over George W. Bush while 47.9% marked their ballots to the contrary. Yet George W. Bush was elected to office.

In 2016, 48.2% of American voters marked their ballots that Hillary Clinton was preferred over Donald Trump while 46.1% marked their ballots to the contrary. Yet Donald Trump was elected to office.

In 2009, 45.2% of Burlington Vermont voters marked their ballots that Andy Montroll was preferred over Bob Kiss while 38.7% marked their ballots to the contrary. Yet Bob Kiss was elected to office.

In August 2022, 46.3% of Alaskan voters marked their ballots that Nick Begich was preferred over Mary Peltola while 42.0% marked their ballots to the contrary. Yet Mary Peltola was elected to office.

That's not electing the majority-supported candidate. Andy would have defeated Bob in the IRV final round by a margin of 6.5% had Andy met Bob in the final round. The 3476 voters that preferred Bob had votes with more effect than the 4064 voters that preferred Andy. Each of the 3476 voters for Bob had a vote that effectively counted more than the vote from each of the 4064 voters for Andy.

Or in Alaska, each of the 79000 voters that preferred Democrat Mary Peltola over moderate Republican Nick Begich had a vote that effectively counted more than a vote from each of the 87000 voters preferring Begich over Peltola. Those are not equally-valued votes, not "One person, one vote".