[EM] Burlington Vermont repeals IRV 52% to 48%

Bob Richard lists001 at robertjrichard.com
Wed Mar 3 12:49:07 PST 2010

robert bristow-johnson wrote:

> [snip]
> i'm having a little trouble decoding some of this (quoting):
> ___________________
> There are better ways to determine when a plurality is sufficient and 
> when there should be a top-two runoff. For instance, the double 
> complement rule, first proposed in 1994 by Rein Taagepera and yours 
> truly (in Comparative Political Studies). Under the DCR, in any 
> election in which no candidate obtains over 50%+1, there is a runoff 
> if (and only if) the second candidate’s shortfall from majority is 
> less than double that of the leader.
> In other words, if the leader has 44%, he is six percentage points 
> short of 50%. There would be a runoff if the second-place candidate 
> had more than 38%, which is double the leader’s shortfall from 
> majority. If the second candidate is under 38%, the election is over 
> in one round, with the leader’s 44% sufficing. Obviously, the gap 
> required between the top two candidates to avoid a runoff shrinks as 
> the leader approaches 50% and increases as the leading candidate’s 
> plurality decreases–as it should. So with a leading candidate at 40%, 
> there would be a runoff unless the second candidate had less than 30%.
> The DCR is not actually used anywhere, but it was the inspiration 
> behind the rule adopted in 1994 in Argentina when that country junked 
> its US-style electoral college. The Argentine rule is a bit more 
> complex. A leading candidate with 45% wins in one round under any 
> circumstances, even if the runner-up is at 44.99%. And less than 40% 
> for the first candidate necessitates a runoff no matter how far the 
> runner-up trails. But in between 40% and 45%, the first round is 
> decisive only if the leading candidate has a ten-percentage-point lead 
> over the runner-up.
> ___________________
> how does that get us to this artificial 40% threshold?

It doesn't. Forty percent is indeed artificial. The Shugart and
Taagepera double complement proposal is intended to be less artificial.
But it is still an approach motivated by practical considerations of
time and cost. As I said previously, I'm not endorsing it. I agree with
Matt Shugart on a lot of things, but not on this.

--Bob Richard

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