Lorrie Cranor's paper (Re: Coombs' Method)
DEMOREP1 at aol.com
DEMOREP1 at aol.com
Mon Dec 30 16:37:41 PST 1996
Rob Lanphier wrote--
Although the Condorcet criterion is a popular means for evaluating voting
systems, there are some situations in which it is not clear that the
Condorcet winner represents the collective choice.
For example, Fishburn [46] presents a scenario in which five voters must
choose between five alternatives (a, b, c, d, e). The voters hold the
following preference orderings (listed from most preferred to least
preferred):
voter 1: a b c d e
voter 2: b c e d a
voter 3: e a b c d
voter 4: a b d e c
voter 5: b d c a e
Given this preference profile, a is the Condorcet winner. However, an
examination of the number of times each alternative is ranked first, second,
etc., bears the following results:
a b c d e
Voters ranking alternative first: 2 2 0 0 1
Voters ranking alternative second: 1 2 1 1 0
Voters ranking alternative third: 0 1 2 1 1
Voters ranking alternative fourth: 1 0 1 2 1
Voters ranking alternative fifth: 1 0 1 1 2
In an examination of rankings, b appears to be the best choice -- with
equal first ranks to a and more second and third ranks than a -- yet the
Condorcet winner is a.
-----
D-- The 2 times that b is second, he/she is beat by a (voters 1 and 4) . The
time that b is third, he/she is beat by a who was second (voter 3).
Fishburn's example does not mean anything. The head to head concept is
fundamental whether there are 2 choices or 200 choices. Nothing magical
happens when there are 3 or more choices.
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