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Subject: Approval Voting


Here is an excerpt from the mail I sent to Martin on Monday about 
approval voting:

Slashdot had an article last week on different voting techniques so I 
read up.

One of the most interesting things I found was the Arrow Theorem by 
Professor Kenneth Arrow. He won a Nobel prize for the theorem which 
proved that all voting systems MUST be unfair in some way.

I then read up on IRV and found that it has a really nasty behavior 
(besides being incredibly complex). It violates the monotonicity 
principle. In a nutshell this says that voting for a choice you want 
shouldn't make that choice lose and not voting for the choice you want 
should help that choice win. That may seem obvious but it turns out that 
IRV violates it. See <http://www.electionmethods.org/evaluation.html#MC> 
  for an example.

I then discovered another voting system that is trivial to run, can be 
used with Kavi as is and doesn't violate the monotonicity principle. 
It's called approval voting. <http://en.wikipedia.org/wiki/Approval_voting>

The way approval voting works is that if you have N choices then you 
open a ballot and let people put a check next to each choice they can 
live with. Then you add up the results and which ever choice got the 
most votes wins.

Kavi can already do this today. In fact, just about all voting systems 
can do this today. This is just a 'select N entries from M choices' vote 
where N = M. Diane actually used this feature in our IRV ballot for the 
BPEL spec name when she let people select 2 out of the N choices so they 
could indicate a preference for spec name and version number from the 
same list.

So if we use approval voting then we can run the whole thing on a single 
ballot, no fancy math, nothing. Just add up the votes and which ever 
choice got the most wins.

Of course approval voting also has a flaw (remember the Arrow theorem). 
Imagine that we have a vote with 10 people and three choices, A, B and 
C. 6 people strongly support A. 2 people strongly support B and 2 people 
strongly support C. However, 7 people weakly support B and 3 people 
weakly support C. Since people can vote for multiple options this means 
that someone who strongly supports A and weakly supports B but doesn't 
support C would cast a vote for A and B but not C. In that case the 
voting total will be:

A - 6 votes
B - 9 votes
C - 5 votes

So even though over 50% of the group strongly supports A, A still loses.

The reason is that approval voting detects consensus. It explicitly 
looks for the option that the largest number of people can live with.

I actually think the 'flaw' in approval voting is a feature in our case. 
Standards bodies are supposed to be run on consensus and approval voting 
is excellent at finding that consensus.

As such, given that it is simple to run, doesn't violate the 
monotonicity principle and is well designed to detect consensus doesn't 
it make sense for us to switch from IRV to approval voting?

	Yaron


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