Condorcet Election Decision Procedure by 2ZTlEmO


									Condorcet Election Decision
   Avoiding the agenda effect?
   Condorcet Winner Criterion
Each pair of candidates should be
considered in its own separate election
and the winner determined. If there is one
candidate who wins over each of the
others in these 2-way contests, that
candidate (called a Condorcet candidate)
should be the winner of the election.
  The Infamous Pizza Election!
# of          8          5        6         7
           Pepperoni    Ham     Veggie   Sausage

             Ham       Veggie   Ham       Ham

           Veggie      Sausage Sausage   Veggie

           Sausage Pepperoni Pepperoni Pepperoni
        Condorcet and Pizza
• How many two way contests are needed?
 (If you aren’t sure, try it for 3 alternatives.)
• List each contest, with the winner and vote
   Condorcet results
  Type        Number of wins

Pepperoni           0

 Veggie             2

  Ham               3

Sausage             1
Digraph (Directed Graph) Model for
        Condorcet Results

      P     S

      H      V
     Vacation Decision
7     4      8     6     5

GC    BC    DV    DV     GC

BC    GC    BC    GC     DV

DV    DV    GC    BC     BC
 Eliminating the Agenda Effect?
• Whenever the agenda effect is present,
  there will not be a Condorcet candidate,
  and hence Condorcet’s method will not
  choose a winner!
• (If there were a Condorcet candidate, he
  would win from the point where he entered
  any agenda.)
• Condorcet does not eliminate the
  agenda effect!
• An election decision procedure is said to
  be decisive if it always produces a winner
  from among the alternatives.
• Condorcet is not decisive. If there is no
  Condorcet candidate, there will be no
  winner. (If the agenda effect is present, for

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