[EM] Why I think IRV isn't a serious alternative KD

Abd ul-Rahman Lomax abd at lomaxdesign.com
Tue Dec 16 16:56:56 PST 2008

At 08:49 AM 12/16/2008, Kevin Venzke wrote:
>Thus, *all things being equal* (which must
>be kept in mind if it's IRV that is on your mind), I would expect that
>failing LNHarm will provoke more insincerity (and thus destroy more
>information) than failing monotonicity.

Highly speculative. Bucklin probably experiences about the same level 
of bullet voting due to LNH fears as IRV, not much more, because the 
"harm" only happens when a majority isn't found in the first round. 
And it isn't really a "harm," that's an unfortunate aspect of the 
name. What the second vote harms is not exactly the favorite, but the 
first vote for the favorite, and only in the specific pairwise 
election against the additionally approved candidate. It is backing 
up and saying, okay, if my candidate isn't getting a majority from 
favorite votes, this additional candidate is also acceptable to me.

And, sure, that can cause the additional candidate to win. If that 
candidate is also approved by more people than my favorite. (Multiple 
majorities are rare, BTW, I've never heard of one happening in a 
Bucklin election, and I doubt that it ever happened. So, if the 
second vote "harms the favorite," it's because lower-ranked candidate 
got a majority, and the favorite didn't.

IRV can pretend that there is no harm from the second vote for two 
reasons: it eliminates the first candidate before using the second 
vote. The *voter* hasn't harmed the first candidate, because the *method* has.

Requiring that the favorite be eliminated before a second rank choice 
is considered cuts two ways. It prevents this alleged "harm," but it 
also prevents "help." I.e., second rank votes coming from other 
candidates; those are exactly the votes which would allow IRV to find 
a "compromise winner," as Robert's Rules notes. In other words, 
Center Squeeze is a direct consequence of LNH compliance by IRV.

LNH is also incompatible with actual runoff voting when there is 
majority failure, unless the runoff is simply the top two IRV 
candidates. In Vermont, the governor must be elected by a majority. 
If there is majority failure, the election goes to the legislature, 
which votes by secret ballot (Plurality election, if I'm correct) 
from among the top three candidates. The IRV legislation introduced 
by Terrill Bouricius had a ballot instruction included: voting for a 
lower ranked candidate can't hurt your favorite. It wasn't true. Your 
lower ranked vote could cause the election to complete, whereas 
without it, there would be further process, which your candidate 
could win. Even Robert's Rules of Order gets this one wrong.

Interesting, eh? Top three. A Condorcet winner is almost certainly in there!

>IRV has other issues that can lead to a different conclusion, but that
>isn't what I was discussing.
>Kevin Venzke
>Election-Methods mailing list - see http://electorama.com/em for list info

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