[EM] No evidence that IRV doesn't fail. Reasons why it must.

[James Gilmour]

Paul asked: 
> But be 
> honest and give your best guess as to what percentage of the 
> voting population would get beyond 5 while in the voting 
> booth.

The examples I described, where I had voted positively and negatively for all 30 candidates in an
STV-PR elections, were annual postal ballots for the council of an organisation to which I belong.
Electors had the luxury of having some weeks to study a one-page statement from every candidate
published in the election booklet.

>  My guess is not even all of the EM-list subscribers 
> would be as assiduous for an election that had 30 or 40 
> different races in the election, each of which has 3-10 
> alternatives. 

We don't have this problem. The most we ever have is two elections of the same day  -  most commonly
two FPTP elections, both in single-member districts.  In Scotland and Wales we make it a little more
complicated because we hold an FPTP election and a two-vote AMS (= MMP) election on the same day, so
that's three "X"s on separate ballot papers.  But that's all.

As to the behaviour of real electors in real STV-PR public elections, here are some results from an
analysis of the electronic "ballot papers" in the Meath constituency at the 2002 Dáil election.
There were 14 candidates for 5 places.  The two largest parties (FF and FG) both put up 3
candidates. Four smaller parties each put up 1 candidate, and there were 4 non-party candidates.
There were 64,081 valid votes.  There is no restriction of any kind on the number preferences a
voter may mark.

The average number of preferences marked was 4.65.  Every candidate was marked as every possible
preference (1 - 14) by at least some voters.  The smallest group was 46 voters (0.07% of total) for
one of the 14th preferences.  The largest group was 11,534 (18% of total) for one of the 1st
preferences.

Number		Percentage
of Prefs		   of
marked		Voters
   1		  5%	
   2		  7%
   3		33%
   4		19%
   5		13%
   6		  8%
   7		  4%
   8		  2%
   9		  1%
 10		  1%
 11		  1%
 12		  1%
 13		  1%
 14		  4%

The surge at pref 14 is evidence of real negative voting on the part of some electors.  One
candidate attracted 25% of the 14th preferences, another 19% and another 15%, with much smaller
numbers spread across the other 11 candidates.

There was an interesting difference in behaviour between the 'supporters' of the two parties that
both put up 3 candidates.  (Supporter defined here as a voter who gave his or her first preference
to any one of that party's 3 candidates.)  Significantly more of FF's supporters stopped at 3
preferences than did FG's supporters.  The balance was made up at 5, 6 and 7 preferences, with a few
more at 8, 9 and 10 preferences.

	Number
	of Prefs
	marked 	FF	FG
	  1	4%	3%
	  2	6%	5%
	  3	40%	28%
	  4	20%	20%
	  5	12%	16%
	  6	6%	10%
	  7	3%	5%
	  8	2%	3%
	  9	1%	2%
	10	1%	2%
	11	1%	1%
	12	1%	1%
	13	1%	1%
	14	3%	4%

Total number of Supporters:    FF = 28, 786    FG = 17,452
Between them these two parties gained 72% of the first preferences.

So my voting habits are not typical.  But I already knew that.  No one on this list is a typical
elector.  If they were, they wouldn't be here.
James