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

Toby Pereira tdp201b at yahoo.co.uk
Sun Oct 16 03:29:21 PDT 2016

The French presidential election isn't IRV though is it? It's just a two-round system - https://en.wikipedia.org/wiki/French_presidential_election,_2012 In such an election it's much clearer that you might not want to vote for your favourite in the second round than in IRV.
But Jameson, I think your centre squeeze illustration is a good one. I've seen many people (mainly on the Center for Election Science forum) saying that IRV is bad because there are situations where voting for your favourite results in a worse outcome for you, but without an explanation for the mechanism, and when and why anyone might know when not to rank their favourite top.
So as I understand it, you've got three candidates: L, C and R - C is the Condorcet winner. Someone's preference order might be L>C>R, but by submitting that ranking, C gets eliminated first and L could then lose to R in the run-off. But by ranking C first, C would be a sure winner over R in a run-off, so it's a safer vote, especially if your main priority is for R not to get elected.

      From: Jameson Quinn <jameson.quinn at gmail.com>
 To: Jeff O'Neill <jeff.oneill at opavote.com> 
Cc: election-methods <election-methods at electorama.com>
 Sent: Saturday, 15 October 2016, 14:29
 Subject: Re: [EM] Why I prefer ranked-choice voting to approval voting

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. 

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