[Election-Methods] pizza and consensus

Juho juho4880 at yahoo.co.uk
Fri Dec 28 11:12:14 PST 2007

On Dec 28, 2007, at 18:51 , Jonathan Lundell wrote:

> With the pizza example surfacing again (and again and again...), it
> struck me that what bothers me about this example is that, in real
> life, deciding on a pizza is one of the few places where just about
> everybody would use informal consensus.
> (For an introduction to formal consensus: http://www.consensus.net/)
> I've come over the years to the regretful conclusion that formal
> consensus is not workable for most organizations, at least not unless
> some fairly stringent preconditions are met (some are described by
> Butler at the site above; they include fairly explicit agreement on
> group goals, along with a lot of time an patience).
> But for pizza decisions, consensus rules. In particular, we try to
> accommodate singleton minorities with strong negative preferences
> ("concerns" in consensus-speak): anchovy-haters, the allergy-ridden.
> It doesn't matter that sausage and pepperoni is the Condorcet or
> majority winner if there's a vegetarian in the group; we'll find some
> consensus choice (fresh tomatoes and pesto, anyone?), given a little
> time, good will, and discussion.
> (That points up another problem with the pizza example: nobody ever
> seems to go to a pizza parlor with individual portions, or
> heterogeneous pizzas. But that's another problem.)
> I wonder if there isn't a better simple example out there in which
> voting is a better strategy than the alternatives.

Yes, sometimes behaviour in the pizza examples and real life do not  
match. Example environments with better match between real life and  
the discussed concepts would be helpful.

The pizza examples have some  properties like possibility of someone  
being a vegetarian or allergic, and the possibility to stretch the  
examples over meals of several days.

To generalize this, when evaliuation different election methods I  
often miss clear description of 1) the purpose/intent and 2) the  
environment. If nothing is stated my basic assumption is that people  
refer to typical country level political elections.

"Purpose" refers to the sought after behaviour of the election  
method. The pizza examples often pay special attention to voters that  
get an unacceptably bad result (e.g. the vegetarian voter). Methods  
that give different winning probability to the candidates  
proportional to their support serve a totally different intent than  
methods that aim at electing a compromise winner. Different purposes  
favour different methods.

"Environment" is mostly relevant for evaluating the strategic risks.  
The requirements are different for large scale public elections with  
independent voter decision making, and for opinion poll like  
elections where voters have no direct interest to strongly push their  
own favourite alternative, and for elections of few voters with well  
known opinions and strong fighting tradition.

"Environment" is also relevant when discussing the level of support  
some method is expected to have. Proposals may look quite different  
e.g. in countries with a two-party tradition and in countries with  
multi-party tradition. One should also very carefully evaluate the  
reactions of the incumbent politicians and the atmosphere among the  
voters and other interest groups.

Use of descriptive real life like example environments would also  
clarify the different purpose/intent and environment cases listed above.

It would be also good if people would more often indicate the  
intended purpose and environment when they make comments on this list.

I'll come back if I find some example scenarios that would be more  
natural and useful than the pizza examples and other regular stuff.


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