@Sass, thank you for your post.
@sass said in Ranked Robin Disadvantages -:
A few things, all.
@masiarek, if I rank candidate A first, candidate B second, and candidate C third, then I know the order I prefer each, but not by how much compared to each other. If I had a 5-star ballot, I might give A 5 stars, B 4 stars, and C 0 stars; or I might give A 5 stars, B 1 star, and C 0 stars. There’s no way for you to determine how I really feel about B based only on my rankings. However, if I start with a 5-star ballot and give A 5 stars, B 3 stars, and C 0 stars, then you know for sure that I would rank A first, B second, and C third. You can always extract a full set of rankings from a set of scores, but usually you cannot extract a full set of scores from a set of rankings. Scores contain strictly more information than ranks; therefore, a score ballot allows voters to express more information than a rank ballot, i.e. score ballots are more expressive.
This only applies if the score range allows for it. A STAR 0 to 5 ballot does not allow for a full ranking of candidates if there are more than a handful standing, so it's not really very expressive.
@Toby-Pereira, you are overestimating the frequency of Condorcet cycles in real-world elections. As more people have studied the question, the estimates have gone down and down.
Additionally, Ranked Robin fails clone independence in the opposite direction of Choose One Voting. This means that to gain an advantage, a party would have to support entire campaigns of multiple candidates who are seen as identical by the electorate. This is so difficult in practice that it legitimately can be dismissed as a real concern. Candidates like to differentiate themselves from each other, electorates do not behave predictably, and campaigns are egregiously expensive. These difficulties are further amplified under a method like Ranked Robin that incentivizes candidates to appeal evenly to the entire electorate (see @Marcus-Ogren’s new paper on Candidate Incentive Distribution).
A party could field two candidates, or if that's not allowed, then essentially get round it by having a B party that's basically the same. These candidates would not want to differentiate themselves from each other because they'd be there as part of a grand plan.
In any case, it's not just about intentional cloning. It's like how IRV fails monotonicity. An IRV proponent might say that it's too hard to vote strategically to take advantage of this, but that doesn't matter. It might affect things anyway. Ranked Robin's lack of clone independence could affect a result, intentionally or not.
Also, if there’s not a Condorcet winner, then there are multiple scenarios more likely than a top-3 cycle that Ranked Robin resolves simply. Check out the electowiki.
I'm not sure exactly what I'm looking at. It's quite a long article. What's more likely than a top-3 cycle when there isn't a Condorcet winner?
Furthermore, your claim that Ranked Pairs is simple is…absurd. I canvass for STAR Voting, a far simpler method, every day, and it truly is at the limit of what we can expect lay voters in America to digest.
Simplicity actually is the most important factor for a Condorcet method because…it’s a Condorcet method. By that metric alone, it excels at both accuracy and honesty, and is also sufficiently expressive.
Ranked Robin may well be simpler than Ranked Pairs, but I still think Ranked Pairs is a relatively simple method. Plus, the way Ranked Robin is presented on that wiki article, it doesn't look simple. Those 8 levels of when there is a tie - what is going on there? It's horrific.
Also, other than Ranked Pairs, there's also Benham's Method. This is just elect the Condorcet winner if there is one. Then eliminate the candidate with the fewest top ranks and carry on until the is a Condorcet winner. Like IRV except the winning condition is being the Condorcet winner rather than having >50% of the votes. This is fairly simple too and cloneproof.
Or something like Smith//Score.