[EM] National Popular Vote & Condorcet

Dave Ketchum davek at clarityconnect.com
Thu Jul 2 14:03:56 PDT 2009


On Jul 2, 2009, at 12:35 PM, Raph Frank wrote:

> On Wed, Jul 1, 2009 at 10:34 PM, Dave  
> Ketchum<davek at clarityconnect.com> wrote:
>>    Approval data - needs thought but my initial thought is as if each
>> approval was a plurality vote - does mean a voter approving 2 gets  
>> 2 votes
>> counted but relative counts per candidate comes out ok.
>>    IRV or Range - examples of methods that should be avoided by  
>> states
>> willing to have their data included - unless they are willing and  
>> able to
>> convert to a method that is supported.

To summarize my thinking:

Each state controls how it interacts with its voters - so let them  
choose their own way, such that their voters' desires get properly  
added into the national X*X array.

> I would group them as
>
> Plurality:
> A vote for candidate A is considered
> A>(others)

This reads as giving the same power as if ranking ONE candidate in  
Condorcet - simple and declarably accurate.
>
>
> Condorcet:
> Matrix is provided directly
>
> IRV:

Here the voters could have ranked exactly as in Condorcet, but  
standard IRV counting does not extract all that the voters say.  I  
would leave it to the state - perhaps they will do an X*X matrix.  I  
do not like what I read below - better for such states to avoid such  
as IRV when  they do not fit with what is reasonably the standard.
>
Summary:  Presumably this state does  IRV for races it controls.  It's  
voters, and those thinking in other states, would like something other  
than what follows for this race in this state.

> Extract as much info as possible, for example
>
> Round 1:
> A: 100
> B: 82
> C: 41

>
> D: 13
>
> 100: A>(others)
> 82: B>(others)
> 41: C>(others)
> 13: D>(others)
>
> D elliminated
> 4 go to A
> 3 go to B
> 5 go to C
> 1 untransferable
>
> Votes are now
> 100: A>(others)
> 82: B>(others)
> 41: C>(others)
> 4: D>A>(others)
> 3: D>B>(others)
> 5: D>C>(others)
> 1: D (so effectively D>(others)
>
> C would then be eliminated and we would get info about 2nd choices for
> C.  One issue here is that C>D>A would not be distinguished from C>A
> (as both would transfer to A).
>
> Approval/Range

For approval my first thought is that they are presumably doing  
approval and my first choice for them is whatever Condorcet states do  
when their voters vote with approval thinking.

For Range the thinking is much as I do above for IRV.
>
>
> This are somewhat different versions of the same method.  There isn't
> any way to reverse the process back to votes.
>
> You give each candidate a plurality vote of (votes obtained)*[votes
> cast/total approval].  This would at least mean that the state
> wouldn't be over represented.
>
> If there were 1000 votes cast and the results were
>
> A: 800
> B: 400
> C: 300
> Total 1500
>
> Then, the results would be:
>
> A: 800/1.5 = 533
> B: 400/1.5 = 267
> C: 300/1.5 = 200
>
> I you assume that voters will use the strategy of vote for their
> favourite of the top-2 and all they prefer to the expected winner, you
> could estimate the preference table.
>
> It is possible to find a matrix that matches the approval results, but
> there wouldn't be a unique one.
>
> For example:
>
> "Add" A's 800 approvals
> 800: A
> 200:
>
> "Add" B's 400 approvals
>
> 800 split into:
> 480: A
> 320: A+B
>
> 200 split into
> 120:
> 80: B
>
> Total
> 480: A
> 320: A+B
> 120:
> 80: B
>
> and so on.
>
> That would result in an assumption that  lots of votes cast blank  
> votes.
>
> Another option would be to find the "top-2".  This could be the 2 most
> approved candidates, W (winner) and S (second).
>
> It is assumed that W and S voters would not approve each other to the
> greatest extend possible.
>
> So, the above example becomes
>
> From the results:
>
> A: 800
> B: 400
> C: 300
> Total 1500
>
> A and B are top-2, if 800 approved A and 400 approved B, then at least
> 200 must have approved both.  This assumes
>
> 600: A
> 200: A+B
> 200: B
>
> This means that every voter is assumed to approve one of the top-2.
>
> The rest of the candidates could then be assumed to be random.
>
> The full process would be
>
> 1) Assume all ballots are blank
> 2) Process Candidates from most to least approved
> 3) If any ballots are blank, then designate them as approving the
> current candidate
> 4) Distribute any remaining approval for the candidate randomly
> 5) Goto 2
>
> This gets you a set of approval ballots which is consistant with the
> results.  Also, it is likely to be reasonably accurate, based on the
> assumption that each voter only approves one of the top-2.
>
> It can be gamed if a party runs 2 candidates, as then every voter is
> considered to vote for one of their candidates.
>
> One option would be to fill blank ballots and then ballots approved by
> all the other candidates (bar the most approved).






More information about the Election-Methods mailing list