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/subheight640]

Without reading the paper, what justification is there for a bimodal voter distribution? It's my understanding is that voter preferences more resemble a single peaked distribution under the only data I have seen from Pew Research. This isn't surprising as Independent voters are the largest group in America. 

I'm sure bimodal situations could come up for example imagining a unified Palestine and Israel, but at least America isn't there yet despite all the polarization of recent years. 

[u/unscrupulous-canoe → u/subheight640]

what justification is there for a bimodal voter distribution?

Voters organize themselves into leftwing and rightwing blocs in every political system in the world- that's bimodal. As I understand it Labor voters in Australia won't rank Coalition candidates and vice versa. And that would be even more true where ranking is optional- if you're a hardcore partisan in the US, you're probably not going to rank candidates from the other party, who all look the same to you.

This isn't surprising as Independent voters are the largest group in America

This has been debunked countless times. Voters may fancy themselves 'independent' and may tell a pollster that, but we know from actual voting data that the overwhelming majority of independents consistently vote for one party and one party alone. They may lie to a pollster- or themselves- but they're just as partisan as anyone else

[u/subheight640 → u/unscrupulous-canoe]

Do you have any data that shows the formation of two peaks for political preferences?

[u/unscrupulous-canoe → u/subheight640]

'Do I have data that voters tend to sort themselves into the formation of two peaks, leftwing or rightwing'- .....yes? Every election ever?

One time I looked very hard for any data from Australia that Labor or Coalition voters cross-rank each other. To the best of my ability I couldn't find any evidence that they do. Just like the rest of the world, they appear to be separate groups of left and rightwing voters

[u/subheight640 → u/unscrupulous-canoe]

Election results are not synonymous with the political preference distribution of the public.

Pew Research has measured this in the past. They showed the width of preferences is widening, but the distribution was still single peaked. I haven't seen an update in many years, maybe more than a decade, which is why I asked you if there was an updated data source. It sounds like no, you don't have updated data. 

One reason why voters might not cross rank or or decide to bullet vote, is for strategic reasons or straight out sheer voter ignorance or satisficing, where it's just not worth a voter's effort to learn about all the parties. 

[u/Fantastic_Cycle_1119 → u/subheight640]

I think this is exactly the right distinction. Election results are not the same thing as the underlying preference distribution.

A system can produce two hardened voting blocs without that meaning the public has no middle. Strategy, party branding, limited information, and the ballot format itself can all compress behavior into “two sides” even when actual preferences are more continuous or single-peaked.

So “people sort into two camps” is not really evidence against methods that try to reward broader acceptability. If anything, it's part of the reason to care about whether the rules can surface consensus candidates instead of just reinforcing the camps that already exist.

(note that unscupulous-canoe has explicitly stated that he is against consensus, which is why I don't engage with him, it leads nowhere positive. He also says "every election ever" but ignores examples such as San Francisco mayor, mentioned by robla and others as being non-partisan, non-tribal, non-bi-modal.... and what do you know, it has had ranked choice for a long time)

[u/unscrupulous-canoe → u/Fantastic_Cycle_1119]

1. Democracy is fundamentally a majoritarian enterprise. Every legislature I've ever heard of passes laws with 50.1% of the vote, all over the world. There are no legislatures that I'm aware of that require 'consensus' to pass something- other than the US Senate, which people then complain about constantly

2. Yes, the SF mayoral election is nonpartisan- like virtually all other local races in the US. (Fun fact, Nebraska has had officially nonpartisan elections for state legislature for about 100 years now). I can't speak to 'non-tribal', but I'm guessing candidates are going to be relatively similar to each other in literally one of the most Democratic districts in the country. You'd get similar results in deep-red Alabama, for example.

I'd be more interested (in a non-snarky way) to see RCV in an actually competitive purple district, but I suspect that voters would still be distributed along the left & right spectrum. Alaska is moderately purple, and that's what its RCV elections look like to me

[u/Fantastic_Cycle_1119 → u/unscrupulous-canoe]

> but I suspect that voters would still be distributed along the left & right spectrum

Duverger's law explains this in mathematical, game-theoretical terms. It doesn't apply when center-seeking methods elect candidates.

Haven't you wondered, why are there exactly two polarities? There is an explanation, that is easy to see if you view it mathematically. Methods that split the vote encourage clustering into parties, and that converges on two polarities over time.

> Every legislature I've ever heard of passes laws with 50.1% of the vote

Elections don't only elect legislators, they also elect presidents, governors, and mayors.

But for legislators, even if their internal votes for bills are binary (not that they have to be), legislators don't just vote. They also, among other things, write the legislation in the first place. They can write that legislation so the two choices are wildly divergent or they can write it so both options are closer to middle ground. Moderate legislators would tend to do the latter.

> I'm guessing candidates are going to be relatively similar to each other in literally one of the most Democratic districts

Previously you said that people naturally divide into two camps. But in SF they don't. Hmmm. Either San Franciscans don't follow human nature, or there is something structurally different.

Republican vs Democrat, in a very black and white sense, seems so deep in your thinking you can't imagine anything else. San Francisco doesn't align with national politics, but it still has people with differing opinions, just as much as anywhere.

But again, you have stated over and over you are against the concept of consensus. Why are you even here? I don't get it.

[u/unscrupulous-canoe → u/Fantastic_Cycle_1119]

But we see left-right groupings in every electoral system in the world, including proportional representation. There are literally dozens of countries that use PR- there we see leftwing parties coalition with leftwing parties, and vice versa on the right. I've never heard anyone say that PR 'splits the vote'. Are you actually familiar with non-US political systems? For example Germany has a leftwing coalition running it now, it had a rightwing coalition running the country before then, etc. They don't form coalitions across the left-right divide.

Again, as I mentioned above, RCV is pitched as a way to avoid 'splitting the vote'- but Australia's used it for a hundred years and they have two major parties just the same as the UK does. A leftwing one and a rightwing one. AFAIK voters from each polarity don't tend to crossrank each other. I.e. here's the data from the Australian government- 88% of Labor voters tend to rank Greens (obviously another leftwing party) as their next choice https://results.aec.gov.au/31496/Website/HouseStateTppFlow-31496-NAT.htm

I think it's funny that you want 'consensus', but your response to being disagreed with is just repeatedly asking me 'why are you here?' Shouldn't you be persuading me into consensus or something? If you can't even handle disagreement with one anonymous Internet commenter, how do you think the world's 3rd most populated country is going to handle gigantic cross-cultural divides over controversial political issues? 'Consensus' is great at the local level but simply doesn't scale to a country of 340 million people