[EM] Why IRV is better than Condorcet

Warren Schudy wschudy at WPI.EDU
Sun Aug 8 09:34:55 PDT 2004

On Thu, 29 Jul 2004, Bill Clark wrote:

> On Thu, 29 Jul 2004 18:57:11 -0400 (EDT), Warren Schudy <wschudy at wpi.edu> wrote:
> > One way of summarizing that point that makes IRV look a little less good
> > is: IRV is provably unpredictable.
> I don't follow you.  What do you mean by "unpredictable" here?

In my message, I had confused correlation and causality. I've 
reconstructed below what I should have said.

A system is unpredictable if you cannot determine how the system will 
behave without doing too much work. (Yes, too much is in the eye of the 
beholder. Squaring a number is usually considered an ok amount of work, 
but evaluating a large summation term by term is often too much).

IRV is this way - most questions about an IRV election cannot be answered 
without running a simulation.

Unpredictability is correlated with difficult optimizations problems. If 
you truely know nothing about a system other than how to simulate it, 
optimization requires exhaustive search. Only if you understand the system 
is some other way (i.e, derivatives, bounds, etc) can you optimize it 

In this light, my statement should have been:

The NP-completeness of optimizing strategies is an expected consequence of
the unpredicability of IRV.


| Warren Schudy                           |
| WPI Class of 2005                       |
| Physics and computer science major      |
| AIM: WJSchudy  email: wschudy at wpi.edu   |
| http://users.wpi.edu/~wschudy/          |

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