[EM] Approval vs. IRV

Bart Ingles bartman at netgate.net
Sat Oct 16 20:40:55 PDT 2004

James Cooper wrote:
> So I'm down to looking at IRV vs. Approval (Approval being completely
> trivial to explain).
> The Center for Voting and Democracy (a group I generally agree with)
> has stated its preference for IRV over Approval.  There are two
> relevant links:
> http://www.fairvote.org/irv/approval.htm
> Article in Science magazine:
> http://www.fairvote.org/op_eds/science2001.htm
> The most compelling argument against IRV in my mind is the empirical
> evidence from Australia.  3rd party candidates are still not viable,
> and voters still vote tactically.  The requirement to rank all the
> candidates also results in some odd side effects (like 'how to vote'
> cards, and the horrific 'donkey vote').
> The most compelling argument against Approval voting from the Science
> mag article is the idea that it will result in non-substantive
> campaigns where candidates try to come across as totally inoffensive
> in order to gain approval from as many voters as possible.  

I don't see it.  'Inoffensive' meaning 'civil', sure, but with Approval, 
  a candidate has every incentive to offer honest criticism of his 
opponents.  Gaining approval from voters who would initially support 
another candidate is only half the story; a candidate must also try to 
minimize the number of approvals received by the other candidates.

It's too bad the CVD didn't see fit to include Brams & Hershbach's 
response to the CVD letter.  Below is a copy I received via e-mail; it 
may differ slighly from the published response due to editing by the 
magazine publisher.

Bart Ingles

IRV is a special case of a voting system proposed by Thomas Hare of 
England (and others) 150 years ago.  It sounds attractive but, when 
compared with approval voting (AV), has some decidedly unappealing 
features, including
° its propensity to lose majority candidates, especially centrists, who 
may do poorly when challenged from both the left and right.  Even when 
there are only three candidates, it is not uncommon that the centrist 
comes in third, which means that he or she loses under IRV.  By 
contrast, AV tends to help such candidates, because they draw approval 
from their opponents' supporters on both the left and right, who want to 
avoid at all costs helping the candidate on the opposite side of the 
political spectrum.

* its nonmonotonicity, which means that raising a candidate in one's 
ranking can cause him or her to lose.  This can occur because of the way 
in which candidates are sequentially dropped and their votes transferred 
to those who remain in the race.  This perverse property of IRV was 
discovered only about 30 years ago.  It is antithetical to the very 
notion of democracy-that, by expressing a stronger preference for a 
candidate, one helps that person.  By contrast, expressing approval for 
additional candidates under AV can never hurt them and may help them.

* its complexity, which even mathematicians have not fully understood, 
as witnessed by misstatements they have made about the Hare system.  It 
is noteworthy that the American Mathematical Society, after long debate, 
abandoned the Hare system for AV.  In fact, none of the seven 
professional societies that have adopted AV over the last 15 years has 
reconsidered its decision and chosen a different voting system.

It is true that AV is a binary system, but not with respect to where 
voters draw the line between acceptable and unacceptable candidates. 
Thus, if there are five candidates, a voter might reasonably approve of 
one, two, three, or four out of the five candidates.  The voter is 
sovereign in deciding who is worthy of approval, whereas IRV forces 
voters to make a strict ranking, which may be asking too much for those 
who do not know a great deal about the candidates but do know who is 
basically acceptable and who is not.

It is also true that AV may not always elect the first choice of a 
majority of voters.  But that result, surprisingly, is sometimes 
desirable.  If, for example, 50 voters rank three candidates XYZ (in 
that order) and 49 voters rank them YZX, AV will elect Y if the 50 XYZ 
voters approve of both X and Y, and the 49 YZX voters approve of either 
Y or both Y and Z.  Is not Y the better social choice, compared with the 
IRV winner, X, whom nearly half the voters consider the worst choice?

Our critics make two false claims.  A sincere ranking under IRV is not 
always optimal-a voter can sometimes ensure the election of preferred 
candidate by not being sincere.  The American Political Science 
Association (APSA) does not use IRV.  To the embarrassment of one of us 
(Brams), a political scientist and a member of the APSA, the APSA does 
not have competitive elections for any of its offices.

We think their charge that AV would force all candidates toward a 
lowest-common-denominator position of blandness is erroneous.  In a 
detailed study of the 1980 presidential election, which had a 
significant third-party candidate (John Anderson), Peter Fishburn and 
one of us (Brams) showed that Ronald Reagan would have won under AV, 
based on both election and poll data (1).  We strongly doubt that AV 
would have compromised Reagan's strong convictions or his campaign 
behavior-or affected the outcome.  Indeed, trying to be everything to 
everybody is likely to make a candidate not even minimally acceptable to 
many voters and, therefore, not a smart campaign strategy under AV.

Our critics point to the serious interest in IRV.  We would point to the 
failure of the Hare system, after being adopted in several large U.S. 
cities like New York about 50 years ago, to stand the test of time.  The 
last city still to use the system in the United States is Cambridge, MA.

Serious analysis of AV began only about 20 years ago.  Since then AV has 
gained many adherents both inside and outside the scientific community. 
  Both its compelling theoretical properties and its simplicity commend 
it for practical use, which cannot be said for IRV in those 
jurisdictions that do not already have electronic voting equipment that 
would permit voters to rank candidates.

Steven J. Brams
Dudley Herschbach

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