[justinpombrio]

For anyone like me who hadn't heard of Gibbard's theorem, it's actually even simpler (and more depressing) than Arrow's theorem. To quote Wikipedia:

For any deterministic process of collective decision, at least one of the following three properties must hold:

1. The process is dictatorial, i.e. there exists a distinguished agent who can impose the outcome;

2. The process limits the possible outcomes to two options only;

3. The process is open to strategic voting: once an agent has identified their preferences, it is possible that they have no action at their disposal that best defends these preferences irrespective of the other agents' actions.

https://en.wikipedia.org/wiki/Gibbard%27s_theorem

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So basically, it's impossible to completely eliminate strategic voting. No matter the method: ranked vs. cardinal vs. anything else you dream up can't help.

[godelski]

> it's impossible to completely eliminate strategic voting. No matter the method: ranked vs. cardinal vs. anything else you dream up can't help.

I think this comment is a defeatist at best and deceitful at worst. Just because there is no global optimization does not mean that all optima are equal. We can in fact have optima that are better than one another (including all optima we know about!). This is a common feature of highly dimensional solution spaces.

The big issue here is that not all criteria are weighted equally, by desire of effectiveness. So we find an optima where we optimize features that have a large weights and care less about optimizing features with small weights. By doing this we can compare systems in their desirability and select the best ones. This is not cause for throwing up your hands and giving up.

As an example: cardinal systems, when compared to ordinal (ranked) systems, are more resilient to strategic voting and simpler (both for the voter and for the people tallying the votes, aka transparency). The cost? Slight decrease in maximal VSE. BUT if we look at the min, mean, median, or modes of VSE given different strategies cardinal system outperform ordinal (aka, desirable). You can see this by comparing with this chart[0]. For example with STAR0-10 we have maximal VSE of .983 and minimal of .912 (actually this makes it strictly better than plurality!). But if we look at our best ordian, RP, we see RP has a maximal VSE of .988 and minimal of .870. So on terms of maximal there's a 0.005 difference but on minimal there's a difference of 0.042! We can easily tell here that STAR is much more resistant to strategic voting than RP (Shulze is even worse!). Doing the same for IRV we see .07/.115 (max/min comparison of STAR0-10 vs IRV on VSE).

So we can compare. We can select better methods. But is there a ''perfect,, solution? No. But don't let the lack of the ability to create a perfect system detract from the ability to compare systems. Not all is lost.

[0] https://electionscience.github.io/vse-sim/vse.html

[justinpombrio]

> I think this comment is a defeatist at best and deceitful at worst.

Wow, very HN! I don't actually mind very much, but seriously, consider applying the principle of charity?

I agree with you, and did before you wrote this comment too! Hence my use of the word "completely". I was just surprised that strategic voting couldn't be completely eliminated; before yesterday I expected that you could, in exchange for losing other nice properties. Of course being impossible to eliminate completely doesn't mean it shouldn't be minimized.

[pksebben]

according to Wikipedia:

>Gibbard's theorem states that a deterministic process of collective decision cannot be straightforward, except possibly in two cases: if there is a distinguished agent who has a dictatorial power, or if the process limits the outcome to two possible options only.

.. it also mentions that gibbard's is specifically about irv.

All that aside, I can't understand the idea that we only get to change things once. My understanding of history is at odds with the concept.

[justinpombrio]

> .. it also mentions that gibbard's is specifically about irv.

No, Gibbard's is not limited to any particular voting method. I think you're misreading the next paragraph (and also confusing IRV, which is a particular method, with ranked choice, which is a whole category of methods). Note the distinction between Gibbard and Gibbard-Satterthwaite:

> A corollary of this theorem is Gibbard–Satterthwaite theorem about voting rules. The main difference between the two is that Gibbard–Satterthwaite theorem is limited to ranked (ordinal) voting rules: a voter's action consists in giving a preference ranking over the available options. Gibbard's theorem is more general and considers processes of collective decision that may not be ordinal: for example, voting systems where voters assign grades to candidates.

[godelski]

> it also mentions that gibbard's is specifically about irv.

This isn't true

> I can't understand the idea that we only get to change things once.

Those of us concerned about IRV and promoting cardionality actually looked at history. Between 1910 and 1920 40 US cities used Bucklin voting (similar to IRV, slightly better even) and all repealed them[0]. So looking at history we see that people recognized the need for a better voting system, implemented something similar to IRV, saw that it didn't make things better, and subsequently said "fuck it, we'll go back to FPTP because it is easier." (I should also mention that in Australia, since 1949, 90% of Lower House elections, which use IRV, are equivalent to using FPTP[1])

So we're looking at history (and modern times) and saying "hey, this didn't work and actually ended up causing us to take a step backwards. Maybe we shouldn't repeat the same mistake."

I hope this clarifies our differing understanding of history.

[0] https://clayshentrup.medium.com/momentum-e5fd12ffce2a

[1] https://en.wikipedia.org/wiki/Australian_House_of_Representa...

[pksebben]

A little, I think we may have different ideas about what the difficulties were in the early 1900s vs now - I believe that the circumstances are different enough now that broad conclusions about what is and isn't feasible cannot be drawn, but that's just a piece of the puzzle and I think your point deserves merit.

What I would ask, then, is rather than not doing IRV, what should we do, in your opinion?

I'm looking at this as a sort of crisis situation, as our ability to affect our politics is in a state of constant erosion, and the process of capture at work here can only end in systemic collapse - the further power gets concentrated, the more centralized our decision making becomes, and the more vulnerable we become to systemic single point of failure.

I would love to see STAR voting become a thing. I think of IRV in the current context as a proof-of-concept that might show people that we can change the structure of voting. I can't see anyone wanting to go back to FPTP, because I don't really see anyone who thinks it's even remotely working.