[EM] Can someone point me at an example of the nonmonotonicity of IRV?

[Juho]

All election methods have vulnerabilities. These monotonicity  
failures may look bad on paper but in real life elections they are  
typically not that harmful. If some IRV voter asks if he should vote  
sincerely or falsify his vote somehow due to the non-monotonic  
properties the general recommendation is anyway to vote sincerely. It  
is not easy to use the monotonicity failures to intentionally improve/ 
falsify the results (in typical large public elections).

There are thus different kind of vulnerabilities. Some may make the  
methods unusable while some are just theoretical vulnerabilities with  
no significant practical impact on real life elections.

My favourite approach is to study and list all these properties and  
then assess their impact in real life elections as sincerely as we  
can (i.e. trying to avoid hiding the problems, exaggeration, negative  
campaigns etc.). Maybe this one should be listed as one of the  
vulnerabilities of IRV but as a relatively harmless one.

Juho



On Aug 9, 2008, at 21:55 , Kathy Dopp wrote:

> On Sat, Aug 9, 2008 at 10:30 AM, Chris Benham  
> <cbenhamau at yahoo.com.au> wrote:
>>
>>
>> Unfortunately it is true that a subset of voters can make their  
>> sincere
>> first choice X lose by by top-ranking X  *instead of top-ranking some
>> other candidate Y*, but  NOT by top-ranking X instead of staying  
>> home.
>>
>
> Can you imagine knowingly supporting a voting system where voters have
> no idea how to rank their first choice candidate (first or last or in
> between) in order to help their first choice candidate win?!
>
> I.e. ranking one's first choice candidate LAST, may help one's first
> choice candidate win, whereas ranking one's first choice candidate
> FIRST will not.
>
> IRV proponents seem to have nothing better to do than to try to screw
> up our voting systems more than they are already screwed up.
>
> So if Australians all jump off a cliff into an ocean full of sharks,
> then the U.S. voters should too?
>
> Chris, I'll never understand your thinking, thank goodness.
>
> Kathy
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