[EM] Condorcet vs RV

[Michael Ossipoff]

I’d said:

Range Voting isn't a bad method, and it's very winnable, but let's not get 
carried away and say that RV is as good as Condorcet.

Warren replies:

--my earlier post which stimulated this, was merely claiming that, as a 
matter of experimental fact, Range Voting produces Condorcet winners more 
often than Condorcet methods do. At first this statement seems impossible by 
definition, but the reason it is true is I am speaking of a 50-50 
honest+strategic voter mix

I reply:

So you’re making unjustified assumptions about how people will vote. You 
seem to be assuming that people will vote as sincerely in RV as they would 
in wv Condorcet. Not a safe assumption.

Warren continues:

, and asking what it the probability the winner is the same as the (honest 
voter) Condorcet winner. My computer sims showed that range voting does so 
more often than Condorcet methods based on rank-order ballots. Paradoxical 
seeming. But true. Since this is an experimental fact, it is indisputable.

I reply:

It’s indisputable in the world of your simulation. To claim that it’s 
indisputable outside that world is to assume a lot. You’re assuming that the 
premises on which your simulation is based are all correct, including your 
assumption that people will vote as honestly in RV as in wv Condorcet. 
Always be careful when drawing conclusions about the real world from 
simulation results for single-winner methods. With apportionment, 
simulations are more reliable, if we know the form of the state-size 
frequency density distribution.


Warren said:

Computer simulations. The page discussing this is 
http://www.rangevoting.org/StratHonMix.html (Also, same results happen for 
other mixes than 50-50...) CAVEAT: I should note that IEVS presently is only 
doing rank order ballots, I.e. equalities in rankings were forbidden in 
these sims.

I reply:

That invalidates the simulations. Equal ranking is allowed in every 
Condorcet proposal that I’ve heard of, including all the proposals of wv 
Condorcet, such as SSD and BeatpathWinner in particular.

Warren said:

Quite possibly the situation would change in future IEVS versions that will 
permit rank-equalities and wv-condorcet methods. I urge EMers to help me 
program more such stuff into IEVS. The IEVS source code (which continues to 
evolve) is available http://www.rangevoting.org/IEVS/IEVS.c To riposte to 
the caveat, I note that there are theoretical reasons why range voting is 
highly likely to generate honest-voter-Condorcet winers, when the range 
voters are strategic. The theorem is presented at 
http://www.rangevoting.org/AppCW.html .

I reply:

Riker showed that, with any method, a sufficiently well-informed 
strategic-voting electorate will choose the CW every time. It was referenced 
in _Scientific American_, in ‘76 or ‘77. Probably July or thereabouts.

Warren said:

I am not sure that Ossipoff was aware of this theorem

I reply:

As I said, it’s true for all methods.

or that he was aware of my computer-sim results. I want to make it clear I 
am not just ranting the counterintuitive claim that range voting is more 
likely to generate Condorcet winners than Condorcet methods. I am proving it 
via both theorem and computer simulation. (The computer sims are independent 
evidence from this theorem since they were not using the kind of strategic 
voters in the theorem, at all.) In the model of strategic behavior in this 
theorem, range voting with strategic voters generates Condorcet winners 100% 
of the time when they exist. Condorcet methods - even wv-condorcet methods 
with rank-equalities permitted - presumably do so less than 100% of the 
time?

I reply:

Riker’s statement applies to wv Condorcet as well as to RV, and to every 
method.

What you’re missing is that Condorcet wv allows sincere voting much more 
than RV does. That’s why my single-winner criteria have always been about 
how much a method penalizes sincere voting. That’s the subject of all of my 
defensive strategy criteria.



If yes, then range is definitely better than Condorcet methods for the 
purpose of generating Condorcet winners; if no, they are the same.

I reply:

You haven’t proven that RV is equal to or the same as wv Condorcet for 
choosing C.W.s.

It’s all in the assumptions on which your work is based.

Mike Ossipoff