[EM] Range PAV results

fsimmons at pcc.edu fsimmons at pcc.edu
Tue Jun 1 09:52:47 PDT 2010


> Also of note is that even though STV only has access to ordinal
> information, none of the cardinal methods manage to dominate it.

In STV the candidates represent particular voters, and get no additional credit
for pleasing some of the other voters.  In PAV the voters that get satisfaction
from other voters' representatives are considered already partially covered.

Consider, for example, the two winner election profile

10 A
40 A>B(99%)
45 C>A(99%)=B(99%)
 5  C

If I am not mistaken, the set {A,C} would be the STV winner, but {A,B} would be
the PAV winner, whether greedy or exhaustive.

The STV set has perfect proportionality, but the PAV set gives double coverage
to 85 percent of the voters at the expense of 5 percent getting nothing.
 
Consider that (1) in a two winner election a faction of 5% has no guarantee of a
representative, (2) even so in this election if all of the C supporters got
their act together they could have gotten C into the junta, but
(3) they are better off as a whole taking the double coverage.

It seems to me that on the whole, {A,B} is a more representative set than {A,C}.

How does the automatic rating system of the simulation compare them?



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