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Approval Voting versus Instant Runoff Voting

electionscience.org

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Re: Approval Voting versus Instant Runoff Voting

#81

Post by jamesonquinn »

shawabawa3 wrote: post #4

Does Approval Voting really pass the "favourite betrayal criterion"? There are scenarios where if you don't vote for both Good and Ideal, bad will win, and scenarios where if you do vote for both Good and Ideal, Good will win (over Ideal) You obviously don't know which scenario you're in when you vote, so you don't know whether you should vote for both good+ideal or just ideal - both options can cause a worse result…

The "favorite betrayal" criterion is defined mathematically. In your scenario, as long as you approve Ideal, you are not betraying your favorite, even if you also approve Good. The only betrayal would be if you didn't approve Ideal. And in approval voting, there is no way others could be voting so that betrayal would be a good idea.

You are talking about a form of strategic voting — whether or not you approve Good. But it isn't favorite betrayal. In fact, it isn't betrayal at any level. All rational approval strategy (assuming a convex distribution over others' votes) is "semi-honest" in that you never approve a less-liked candidate but not a more-liked one. The only strategic choice is where to set your threshold, then honestly approve all candidates above it.

According to the Gibbard-Satterthwaite theorem, any voting method has some form of strategy, so in that sense the best you can possibly do is ensure that all strategy is semi-honest. Approval is optimal in this sense.

Re: Approval Voting versus Instant Runoff Voting

#82

Post by jamesonquinn »

a_imho wrote: post #37

Sortition is the most democratic way of electing representatives.

Sortition (that is, random selection) is a system for roughly-proportional representation; that is, for choosing multiple winners for a legislature so as to represent a population.

Approval voting is a way of picking a single winner.

They solve entirely separate problems.

(Sortition is nearly optimal if your only goal is to match the distribution of voters by a subset of equally-weighted representatives. Technically, it's possible to improve on it slightly by allowing voters to cluster themselves into a hierarchical structure of parties and factions, then performing sortition under the constraint that each party and/or faction must come within 1 seat of its correct proportional representation. This kind of technique is called "reduced-variance sampling" when used in sequential monte carlo sampling.

But sortition, or party-clustered sortition, pays no attention to candidate quality. Most people would agree that if there are two candidates that hold the same ideology, but the only difference is that one of the two has a medical problem that only allows them to work for 1 hour a week, the other one would make a better representative. Sortition cannot be fixed to take this kind of factor into account, which is a big part of why many people prefer more traditional voting methods.)

Re: Approval Voting versus Instant Runoff Voting

#83

Post by jamesonquinn »

dj-wonk wrote: post #66
PaulHoule wrote: post #33

Yep, IRV sends you right into the jaws of Arrow's Theorem which is not a nice place to be.

Arrow’s Impossibility Theorem, as I understand it, applies quite broadly to voting systems. To put it simply, you can’t avoid it. You just decide what trade offs you want to live with.

Arrow's theorem applies only to ordinal voting methods. Approval is not actually subject to Arrow's theorem; it's not even well-defined whether it passes the criteria.

However, there are various voting impossibility theorems inspired by Arrow which do apply to approval. Most notably, Gibbard-Satterthwaite.

Re: Approval Voting versus Instant Runoff Voting

#84

Post by [deleted] »

brianolson wrote: post #77
hackinthebochs wrote: post #40

Earlier quoted context omitted.

>because it has bad outcomes and for no additional cost or complexity those ranked ballots could have been counted by a Condorcet method that results in better democracy. Can you show how the differences in outcomes is better using the Condorcet method?

Yes, there was a real world election run using IRV that got the wrong answer. Fortunately the full (anonymized) vote set was released and we can see how it would have gone using other election methods. https://bolson.org/irv/ I've also done simulations of millions of elections with various election algorithms and there are trends about what works and what doesn't: https://bolson.org/voting/twographs.html

[deleted]

Re: Approval Voting versus Instant Runoff Voting

#85

Post by tass »

Vinnl wrote: post #48
tass wrote: post #44

Earlier quoted context omitted.

In their example voting form there is a list of candidate names with a bubble next to each. How can someone “fill in more bubbles for (their) candidate”?

I had the same question, but I think they meant that you can fill in the bubbles for your candidate of choice on other people's ballots without anybody being able to detect it, and without causing the ballot to be discarded.

It's possible that it might be easier to tamper with these than other ballots, but there must already be countermeasures in place to deal with these types of issues in a large scale election.

In Australia, each candidate is able to send a scrutineer to each voting and counting location, and it's not exactly done in privacy where tampering would go undetected: https://www.youtube.com/watch?v=XevjASEgoK8

Re: Approval Voting versus Instant Runoff Voting

#86

Post by hackinthebochs »

brianolson wrote: post #77
hackinthebochs wrote: post #40

Earlier quoted context omitted.

>because it has bad outcomes and for no additional cost or complexity those ranked ballots could have been counted by a Condorcet method that results in better democracy. Can you show how the differences in outcomes is better using the Condorcet method?

Yes, there was a real world election run using IRV that got the wrong answer. Fortunately the full (anonymized) vote set was released and we can see how it would have gone using other election methods. https://bolson.org/irv/ I've also done simulations of millions of elections with various election algorithms and there are trends about what works and what doesn't: https://bolson.org/voting/twographs.html

The behavior graphs seem to use a linear "happiness" metric to judge the quality of outcome. I question this choice. It is not intuitive to me that some unit of happiness should cancel out a unit of misery when it comes to determining election outcomes.

The IRV page extrapolates the majority principle for two choices to more than two choices, but its not obvious that this is correct. There are arguments that need to be made before we can start comparing the quality of outcomes between voting methods.

Re: Approval Voting versus Instant Runoff Voting

#87

Post by jsmith45 »

ClayShentrup wrote: post #72
comnetxr wrote: post #60

Earlier quoted context omitted.

While I would certainly be more happy in a world with either IRV or Condorcet method than FPTP, I think this argument against IRV is too simplistic. The situation is candidates D, R with the largest numbers of voters who prefer them first, and consensus candidate I with smaller first preference than D, R but lots of 2nd preference. Under any Condorcet method, the D and R voters can hurt their candidate by ranking I a…

The Later-no-harm criterion is basically a nonsensical idea invented to make IRV look better than it is. See a Princeton math PhD dissect it here. http://scorevoting.net/LNH tl;dr for non-experts (I co-founded the Center for Election Science and have studied voting methods since 2006). The idea behind LNH is that if I vote for the Green in 1st place, it's "safe" to then rank the Democrat 2nd, because that can't cause…

Doesn't later-no-harm only fail on condorcet methods if there is no Condorcet winner?

From what I've seen of most Condorcet methods, the best way to tactically vote differs if there is or is not a Condorcet winner, and often become a major mistake in the other circumstance.

Basically it means unless you know what the results will be tactical voting will have a rather good chance of backfiring on you, making it not worthwhile, which seems like a good thing to me.

Re: Approval Voting versus Instant Runoff Voting

#88

Post by dj-wonk »

specialist wrote: post #71
dj-wonk wrote: post #67

Earlier quoted context omitted.

I appreciate your opinion, but I want to point out that our definitions of fairness and simplicity may vary. Much of scholarly work around elections systems strives to ground itself on particular formal criteria.

"opinion" Comparative fairness is well documented. This graph is a good appromixation: https://www.electionscience.org/wp-content/uploads/2018/12/c... https://www.electionscience.org/library/approval-voting-vers... Simplicity also accounts for election integrity concerns (ease of tabulation and auditing).

Can you share the context for the graph?

Do you have a formal definition for how you are using ‘fairness’?

Re: Approval Voting versus Instant Runoff Voting

#89

Post by jamesonquinn »

notahacker wrote: post #76
jadell wrote: post #69

Earlier quoted context omitted.

I don't think that's a rare situation at all. There's a large population out there that doesn't identify with R/D (in US politics), but does identify more closely with a 3rd party. But they never vote for them because "tactics". That doesn't mean those people wouldn't find R or D acceptable, it just means the're ideologically closer to a 3rd party. What AV is trying to get at is the situation where the most people ar…

But assuming most of these people consider R and D acceptable but actively prefer the third party (if they consider them equally acceptable FPTP isn't really depriving them of their ideal electoral choice), AV is inferior to most other non FPTP votes like IRV, which accurately represent their preference for the third party first, and the Rs and Ds only if that party can't win. AV has a pretty significant "if I tick t…

IRV actually has the opposite problem: "If I vote for my ideal candidate, am I impairing the good candidate's chance of winning?" For instance, if it were Nader/Gore/Bush with 26%/25%/49%, and (hypothetically) all Nader voters preferred Gore over Bush but not all Gore voters preferred Nader over Bush, then voting for Nader instead of dishonestly choosing the "lesser evil" Gore would end up electing Bush.

No voting method can entirely escape both of these problems. But newer methods like STAR voting balance them against each other and manage to minimize both.

Re: Approval Voting versus Instant Runoff Voting

#90

Post by incog-neato »

fsargent wrote: post #73

It can't be mentioned enough that Approval Voting works with existing voting machines. One of the unfortunate difficulties with IRV is that it often requires a wholesale replacement of the voting infrastructure. The Center for Election Science is a big supporter of IRV as a better system than our current "Choose One" voting method, but we've found that Approval Voting is both more descriptive and less prone to strate…

Is there any real momentum for any kind of change at the US Federal level? Do politicians talk to you? What's the buzz?
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