[lbo-talk] Arrow (Was Re: law)

joanna bujes jbujes at covad.net
Fri Sep 10 10:28:22 PDT 2004


The only real paradox here is #5. But even that strikes me as trivial compared to the actual problems of

-- lack of education -- incessant brainwashing -- gerrymandering -- intimidation/exclusion of minority voters -- fraud

Let's tackle those first...and then see what remains.

Joanna

andie nachgeborenen wrote:


>Warning, Slightly Technical Stuff Here:
>
>Yes, Arrow's results concern voting. But voting is how
>things are decided in a democracy. The math is
>rock-solid. Here's a standard proof:
>
>http://www.tulane.edu/~dnelson/COURSES/IntroPE/arrow.pdf
>
>That, plus the impotrtance of the result, is why Arrow
>won the Nobel Prize, although Michigan didn't find the
>result interesting and (before Arrow won the Nobel)
>turned him down for tenure.
>
>Arrow showed that you cannot have a voting system that
>satisfies the following conditions, four of which seem
>absolutely crucial to any system that calls itself
>democratic:
>
>1) Nondictatorship (no one person's vote decides an
>issue (except as a tie breaker);
>
>2) Monotonicity: No choice can be harmed in a vote by
>being ranked higher by an individual, or (stronger)
>
>2a) Pareto optimality: if everyone prefers a certain
>choice, it will be the outcome society prefers
>
>3)Universality: the voting system can in principle
>rank all choices that citizens might make relative to
>one another
>
>4) Citizen Sovereignty. Every possible ranking of
>choices can be achieved from some set of individual
>votes.
>
>5)Independence of irrelevant alternatives: You should
>not be able to affect the outcome of a vote by
>introducing another choice into it, unless the extra
>choice actually wins (The Nader problem!)
>
>That is, in social choice-ese. the outcome of a choice
>among a limited set of options should be consiststent
>with the choice among all options, so that choices
>outset the subset (irrelevant ones) should not affect
>the choice within it. (This one is the least
>intuitive, but it seems like it should be true).
>
>The theorem is that with two voters and three options,
>you cannot satisfy these conditions at the same time:
>not all choice sets are attainable without violating
>at least one of them.
>
>There is a vast literature on getting out of the
>paradox because it is very trouble to democrats that
>no voting system can satisfy these criteria, all of
>which appear fundamental to democracy.
>
>The problem isn't that no _single_ voting system can
>accurately represent the will of the majority -- you
>can't _combine_ voting systems to avoid the paradox.
>
>The problem rather sugests that there is no such thing
>as "the will of the majority," if that is taken to be
>an aggregate of individual preferences. That of
>course is an interpretation, not a result. It's
>embraced by right wing, market-oriented public choice
>theorists like James Buchanan who want to take
>everything out of the public realm and make choices by
>buying and selling instead. So it is even more
>troubling for the left.
>
>Nonetheless I suggest that nothing, not even a
>mathematical proof, would make us give up our faith in
>democracy. Even the public choice crowd does not
>advocate getting rid of democratic politics, just
>limiting its scope a lot.
>
>jks
>
>
>
>
>--- John Adams <jadams01 at sprynet.com> wrote:
>
>
>
>>On Thursday, September 9, 2004, at 11:24 PM, andie
>>nachgeborenen wrote:
>>
>>
>>
>>>By way of illustration, the economist Kennth Arrow
>>>
>>>
>>has
>>
>>
>>>a theorem -- a mathematical proof -- that four or
>>>
>>>
>>five
>>
>>
>>>absolutely fundamental and completely obvious
>>>conditions for democracy are inconsistent.
>>>
>>>
>>If I remember correctly--seems like David Duke was
>>running for Senate
>>that year, so it would've been '90 when we had the
>>seminar--Arrow's
>>work is specific to voting systems. This was given
>>by the math
>>department, though, so I can't swear whoever
>>presented interpreted him
>>correctly. (Didn't Arrow get a Nobel Prize in
>>economics for this? There
>>was some discussion during the seminar about whether
>>the math of it was
>>worthy--I seem to recall suggesting it was the
>>cleverness of his
>>application of the math that was being recognized,
>>but then, that's the
>>sort of argument I make around people more
>>knowledgeable than myself.)
>>
>>
>>
>>>That doesn't make us think, oops, better go with
>>>dictatorship. It makes us think there is something
>>>funny about Arrow's proof, although no one has
>>>
>>>
>>been
>>
>>
>>>able to say just what.
>>>
>>>
>>I recall the interpretation of his work as being a
>>bit different--more
>>that no single voting system can be guaranteed to
>>accurately represent
>>majority will given all possible election results.
>>It's been a long
>>time, though, and I was busy that fall, so I'm not
>>shocked if I
>>misremember.
>>
>>All the best,
>>
>> John A
>>
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