[EM] Re: approval strategy in DMC ("automated")

Chris Benham chrisbenham at bigpond.com
Wed Sep 14 13:38:34 PDT 2005


>I've made a slight change on the DMC page on electowiki.
>I've extended the definition somewhat:  the ballot is a combination of ordinal
>ranking (equal ranks allowed) and approval rating.  The approval rating
>information can be either binary approval (approved/not-approved) or
>finer-grained cardinal ratings ([1,0,-1] or [100,99,...,1,0]).  I think this is
>more of a difference in implementation than the method, since the initial
>ordering is by total approval.
>In the above case, a more graduated cardinal rating (say 100-0) would allow a
>voter to approve weaker candidates with a low, but non-zero, rating.
Using fine-grained  CR ballots with some range like 0 to 100, or even 
-100 to 100, so that there are always
many more possible grades (slots) available than there are candidates 
allows at the cost of greater counting
complexity  what is in my opinion a big improvement:

(1) Inferring rankings from ratings, eliminate non-members of the 
Schwartz  set.

(2) If more than one candidate remains, "interpret" each  ballot to be 
approving those remaining candidates that it
rates higher than the mean of  it's ratings of the remaining candidates, 
and half-approving  those that it rates at exactly
this mean (and of course not approving those it rates below.)

(3) Based on the inferred rankings  and the step(2) construed approvals, 
use  Definite Majority Choice (DMC) to
elect the winner.

The idea is that voters don't need to have any idea of what the chances 
of any of the candidates being elected are, and
voters who (in the "manual" version) would approve or not approve all 
the candidates except one sure loser are not
unfairly disadvantaged.
A while ago I proposed  "Automated-Approval Margins" which is identical  
except  that in step(3)  "Approval Margins"
replaces "DMC".  Also possible would be in step (3) to ignore the 
rankings and just use (construed) Approval, but at
the time I looked at that and decided it wasn't as good on strategy grounds.

BTW, I think  unadorned DMC with an explicit approval cutoff  (so that 
voters can rank candidates they don't approve)
is an excellent practical proposal for public political elections.   I 
am opposed to  "blindly vote my favourite's ticket" idiot
boxes (which will just give rich parties incentive to sponsor lots of  
"fake" candidates), and to  the proposed rule

> that if some candidate gets more than 66% approval, then the candidate 
> with
> greatest approval wins.

This is an arbitrary complication that would cause the method to fail  
Majority Favourite and  Irrelevant Ballots.

Chris  Benham

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