[EM] Anyone got a good analysis on limitations of approval andrange voting?

[James Gilmour]

> > Robert Bristow-Johnson wrote (9 Nov 2009):
> >
> > "Of course IRV, Condorcet, and Borda use different methods  to tabulate 
> > the votes and select the winner and my opinion is that IRV ("asset 
> > voting", I might call it "commodity voting": your vote is a 
> > "commodity" that you transfer according to your preferences) is a 
> > kabuki dance of transferred votes.  and there is an *arbitrary* 
> > evaluation in the elimination of candidates in the IRV rounds: 2nd- 
> > choice votes don't count for shit in deciding who to eliminate (who 
> > decided that?  2nd-choice votes are as good as last-choice?  under 
> > what meaningful and consistent philosophy was that decided?), then 
> > when your candidate is eliminated your 2nd-choice vote counts as much 
> > as your 1st-choice."

These statements suggest a misunderstanding of how STV voting works and what preferences (US "rankings") mean in the STV voting
system.  In all STV elections, the preferences are contingency choices.  Your vote is transferred to your second choice only in the
event that your first choice cannot secure election or does not need you support to secure election.

This is most easily seen in single-winner STV elections (US = IRV), where the sequence of rounds is exactly analogous to the
sequence of rounds in an exhaustive ballot (eliminating one candidate at a time in successive ballots).  The only difference is that
in an STV (IRV) election you don't know what all the other voters did in Round 1 when you come to give your second choice.  So the
preferences (= contingency choices) marked on an STV ballot are quite different from the preferences marked on, for example, a Borda
ballot where some attempt will be made to use all of the information simultaneously.

The same applies to STV multi-winner elections (STV-PR), though the connection is not so obvious in versions of STV that use
fractional transfer values to remove the otherwise unavoidable element of chance.  However, the contingency choice nature of the
STV-PR preferences is obvious in those versions of STV-PR that use whole vote transfers, e.g. Cambridge MA and the Dáil Éireann.  It
is even more obvious in Thomas Hill's original application of STV-PR when the boys formed lines in the schoolyard to show their
support for the various candidates.

These STV preferences are all quite clearly contingency choices and they should not be interpreted in any other way.

James Gilmour


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