[EM] Why I prefer ranked-choice voting to approval voting

C.Benham cbenham at adam.com.au
Sat Oct 15 08:01:35 PDT 2016


IRV's compliance with the Later-no-Harm criterion is a nice selling 
point aimed at nervous or sceptical voters
who are used to and content with FPP,  but I think it is far from the 
method's greatest feature.

If voters who only care about their favourites can influence the fate of 
other candidates without any risk at all,
that encourages them to express very weak light-minded preferences 
and/or to blindly go along with preference
deals that might be corrupt or cynical and unprincipled.

IRV  also meets Later-no-Help, which I think is a very good thing. And I 
rate IRV as the best of the methods that meet it.

Some weak truncation incentive is desirable, but Approval's is far too 

> Where there are more viable candidates, the cognitive burden is much 
> higher.  The French 2012 elections for President had ten candidates in 
> the first round.  A voter thus needed to consider which candidates had 
> a chance of winning, and then select her favorite among those who had 
> a chance of winning.

A more devious strategy may be available. If the voter is sure that, 
among the candidates with some chance of winning, her favourite will
make it to the final without her help, then she can vote for the 
candidate that (among those with some chance of making it to the top-2)
that her favourite would have the greatest chance of beating in the 
second round.

That is called the Push-over strategy.

A while ago I suggested that one way to improve Top-Two Runoff would be 
to use Approval in the first round, and if the most approved
candidate A isn't approved on more than half the ballots in the first 
round then have a second-round runoff between A and the candidate
with the most approval-opposition to A (i.e. the candidate that is most 
approved on ballots that didn't approve A.)

> I want to briefly address another form of ranked voting called 
> Condorcet voting.  Condorcet voting also uses a ranked ballot, but the 
> votes are counted in a different way.
> While Condorcet voting is a great voting method, ...

"Condorcet voting" isn't  decisive enough to qualify as a "voting 
method".  Condorcet is just a criterion (or a category of methods that 
meet the criterion).

Min-Max Margins,   Schulze (Winning Votes),  Smith//Approval, "Benham" 
(check for a CW among remaining candidates before each IRV-style 
are all very different methods that happen to meet the Condorcet criterion.

Chris Benham

On 10/11/2016 11:24 PM, Jeff O'Neill wrote:
> I recently wrote a blog post explaining why I prefer ranked-choice 
> voting (i.e., IRV or alternative vote) to approval voting.  It is a 
> quite different kind of argument than most of the posts here because 
> it is a policy argument rather than a mathematical one. Nevertheless, 
> I thought people here might find it interesting.  I'd love to hear 
> your comments and any counterarguments as well.
> I've copied the post below and you can also find it here:
> http://blog.opavote.com/2016/10/why-i-prefer-ranked-choice-voting-to.html 
> <http://blog.opavote.com/2016/10/why-i-prefer-ranked-choice-voting-to.html>
> Why I prefer ranked-choice voting to approval voting
> <https://3.bp.blogspot.com/-zufbCki-BVo/V_o1-OKl27I/AAAAAAAAASM/vrix1OAitpsQ4MhGoPunWk38sNcWu-qPwCLcB/s1600/rcv%2Bballot.png>
> Voting is not an easy task for a voter.  I don't mean taking time off 
> work, getting to the polls, and waiting in line, etc.  I mean, when 
> you are standing there in the ballot box, you have to decide what vote 
> you want to cast given the options presented to you.  For example, a 
> Jill Stein supporter may be torn between supporting her favorite 
> candidate and voting for a candidate who has a better chance of 
> winning the election.  I'll refer to this as the /cognitive burden/ of 
> expressing your vote.
> In this post, I'll address the cognitive burden of three different 
> types of voting:
>  1. Plurality voting (i.e., selecting one candidate)
>  2. Approval Voting
>  3. Ranked-choice voting
> OpaVote <http://www.opavote.com/> supports all three of these voting 
> methods if you want to try them out yourself.
>     Plurality Voting
> Plurality voting is very simple, a voter simply picks one candidate.  
> There is, however, a cognitive burden when there are more than two 
> candidates.  A voter presumably wants her vote to matter.  
> Accordingly, a voter should not necessarily select her favorite 
> candidate, but instead select her favorite candidate who has a 
> reasonable chance of being elected.
> Consider the current U.S. Presidential election.  I'm a big supporter 
> of the Green Party, but Jill Stein is not going to win the election. 
> I'd like to vote for the Green Party, but instead I'll vote for 
> Hillary because that is the best way for my vote to make a 
> difference.  Others will vote for the Green Party out of principle.
> Where there are more viable candidates, the cognitive burden is much 
> higher.  The French 2012 elections for President had ten candidates in 
> the first round.  A voter thus needed to consider which candidates had 
> a chance of winning, and then select her favorite among those who had 
> a chance of winning.
>     Approval Voting
> With approval voting, a voter has the option to approve as many 
> candidates as they like. The candidate with the most approvals is the 
> winner. For someone whose first choice is Jill, the voter may, for 
> example, approve of Jill and Hillary and not approve Donald and Gary.
> Approval voting, like plurality voting, is very simple in practice.  A 
> voter just selects one or more candidates.  But Approval voting 
> suffers from similar cognitive burdens as plurality voting. How do you 
> draw the line between candidates you approve and candidates you don't 
> approve?
> Consider a voter whose true preferences are:
>  1. Jill Stein
>  2. Hillary Clinton
>  3. Gary Johnson
>  4. Donald Trump
> Clearly, this voter will approve Jill and will not approve Donald, but 
> what should she do with the other two candidates? Should she also 
> approve Hillary?  Giving Hillary an approval may help Hillary beat 
> Jill, but she would certainly prefer Hillary to Gary or Donald. 
> Similarly, this voter may not like Gary, but she may dislike Donald so 
> much that it is worthwhile to approve Gary to minimize the chance that 
> Donald is elected.
> Phew... that is a lot of thinking to do. It would be even harder if 
> Jill and Gary had better chances of being elected.
> In sum, approving any candidates other than your favorite can hurt 
> your favorite. Not approving candidates can help your least favorite 
> get elected.  Approval voting thus creates a significant cognitive 
> burden for voters.
>     Ranked-Choice Voting
> With ranked-choice voting, a voter ranks the candidates in order of 
> preference, similar to the picture above.  In my view, this has the 
> least cognitive burden among the three methods discussed here.  It is 
> easy for a voter to pick her favorite candidate, pick her second 
> favorite, and so on. This kind of ballot has low cognitive burden 
> because a voter doesn't have to consider which candidates are viable.
> But, you may ask, "Doesn't a voter have to think about whether their 
> second and later preferences might hurt their first preference? For 
> example, should a Jill Stein supporter not rank Hillary second because 
> it might help Hillary beat Jill?"
> The great thing about ranked-choice voting is that the answer to this 
> question is a clear and resoundingNO!!! Your second and later choices 
> cannot harm your first choice! Your second preference is only ever 
> considered at all if your first preference has definitively lost. 
> Voting geeks cause this the later-no-harm criterion 
> <https://en.wikipedia.org/wiki/Later-no-harm_criterion>.
> Voters thus need to be educated that later choices do not hurt earlier 
> choices so that voters are encouraged to rank as many candidates as 
> possible.  The more candidates a voter ranks, the greater influence 
> the voter has in the outcome of the election.
> Accordingly, ranked-choice voting has the lowest cognitive burden.  A 
> voter simply needs to select their first choice, second choice, and so 
> forth.  The voter does not need to consider which candidates are viable.
> (For voting geeks who are leaping out of their seats to make points 
> about other voting systems criteria 
> <https://en.wikipedia.org/wiki/Category:Voting_system_criteria>, 
> please keep reading.)
>     Other Stuff...
> In my view, it is extremely important to make it as easy as possible 
> for voters to vote, and, for the reasons described above, 
> ranked-choice voting does this better than both plurality and approval 
> voting.
> I want to briefly address another form of ranked voting called 
> Condorcet voting.  Condorcet voting also uses a ranked ballot, but the 
> votes are counted in a different way.  Condorcet voting doesn't 
> satisfy the later-no-harm criterion mentioned above, so it is 
> possible that your second and later choices could hurt your first 
> choices.  The possibility, however, that your second and later choices 
> hurt your first choice is so small that, for practical purposes, a 
> voter to cannot take this into account, and thus Condorcet voting has 
> the same cognitive burden as ranked-choice voting.  While Condorcet 
> voting is a great voting method, I still prefer ranked-choice voting 
> for public elections, and I'll address that in a future blog post.
> Another point to mention is that detractors of ranked-choice voting 
> complain that ranked-choice voting does not satisfy other voting 
> systems criteria, such as the monotonicity criterion 
> <https://en.wikipedia.org/wiki/Monotonicity_criterion>.  While this is 
> certainly true, for practical purposes, a voter cannot take the 
> monotonicity criterion into account when casting a vote.  It is just 
> far too complicated and you would need to know how everyone else is 
> going to vote. The non-monotonicity of ranked-choice voting thus 
> doesn't create a cognitive burden.
> Please let me know what you think, especially if you disagree.  I am 
> happy to post any well-reasoned dissent as comments or even give you 
> the opportunity to write your own blog post in rebuttal.
> ----
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