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

Jameson Quinn jameson.quinn at gmail.com
Sat Oct 15 06:29:37 PDT 2016

> But there's an important, and predictable, class of election scenarios
>> where it's strategically crucial NOT to rank your favorite first: center
>> squeeze scenarios. If you have two candidates at ideological opposite
>> points, with a third candidate in the middle near the median voter, it is
>> actually quite common for the center to have the lowest first-choice
>> support and get prematurely eliminated. This kind of thing happened in
>> Burlington 2009; in multiple recent French elections; tragically, in Egypt
>> 2011; and would have happened in the US 2000 if Nader had gotten over 25%.
>> In this case, the correct strategy for one group of voters is to rank their
>> true first choice in second place. Understanding this, and correctly seeing
>> when it applies, is a HUGE cognitive burden for IRV voters.
> When you say that "it is actually quite common for the center to have the
> lowest first-choice support and get prematurely eliminated," we need to
> clarify "quite common."  If you mean 5-10% of the time, then I could
> believe that, but if you mean 50% of the time, then I would disagree.  It
> would be really interesting if a statistician could collect the data and
> present results.

Depends on various factors, but generally I'd put it in the 10%-50% range.
It's happened in 2 of the last 4 French presidential elections so 50% is
not a crazy estimate.

> I can't comment on Burlington or Egypt.  For the French elections, the
> center candidate is generally in the top three of 10-15 candidates
> (depending on the year).  Candidates that came later than that top 5 have
> very little support.

"Generally in the top 3" is no comfort if the Condorcet winner is
eliminated third-from-last.

> My main point here, however, is that, except in rare situations, voters
> are not capable of voting strategically to account for a center candidate
> out of the top two (and by this I mean normal voters, not the people on
> this list).  First, it isn't clear how often the center candidate is out of
> the top two.  Second, voters would need to think deeply about how the
> voting system works.  third, you need precise polling information.  Fourth,
> if you are too successful in your strategic plan, it backfires.  There is
> this middle ground where enough voters have to vote strategically to get
> their desired result but not so many that you overshoot and still elect the
> wrong candidate.  A few people (like the people on this list) may consider
> such a scenario when voting, but I think it is far too complicated for any
> significant subset of voters to consider it.

There are two possibilities. Either voters can strategize effectively, or
they can't. If they can, it's a burden, and it favors the groups who can.
If they can't, then you get unrepresentative results, where a majority
would have favored another specific option. As in Burlington, that can lead
to repealing the system itself.

> This makes sense, but I don't think it matters so much.  For most RCV
> elections, nearly all ballots end up at one of their top 3 or 4 choices.
> Rankings after this don't matter much.  Also, if a person has trouble
> deciding who to rank 7th and 8th, then perhaps the person doesn't have a
> strong preference between them and would be equally happy (or more likely
> equally unhappy) with either.

What if you can't easily distinguish #7 from #8, but you can easily
distinguish either of them from #15, and it turns out that #8 is the only
one who could beat #15?
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