David Gamble wrote:
All single seat
methods are capable of producing bad results.
Of course, they are only bad from some point of view. But yes, I'd
agree with that in principle. That said, some will produce bad
results much more reliably than others.
This is why I believe
that single member methods should only be used for single offices (
mayor, governor, president, etc) and that multi-member bodies should be
elected by proportional representation. There is nothing and can be
nothing that is proportional about the allocation of a single
That's a laudable goal.
single member method is IRV.
That's a pretty big non sequitur there. Why IRV? Simply
because that's what the largest US electoral reform group
Can you really put the Condorcet "nighmare" scenario I wrote in
the same ballpark as the IRV nightmare scenario? My Condorcet
scenario ends with the compromise candidate winning, and nobody
regretting their vote. In the IRV scenario I showed, the clearly,
indisputably preeminent candidate loses, and a third of the electorate is
kicking themselves on election night.
multi-member method is the single transferable vote. It is considered an
important principle in STV that lower preferences should neither help nor
harm higher preferences. The reason for this is that if by casting a
lower preference you can defeat a higher preference you are given a
powerful incentive not to cast lower
This is also true of winning votes Condorcet the vast, vast majority of
the time. The scenario you mention below is no exception.
The election was to close to call, before the votes were counted it was
uncertain whether A or C would obtain the most first preferences ( and
also irrelevant considering A and C supporters second
Under Condorcet by casting a second preference for compromise candidate B
both A and C voters have effectively defeated their first choice and
This is totally untrue. As Kevin pointed out, they have only beaten
the OTHER candidate, their least favorite, by casting second place
votes. Nobody in this election was hurt by their second place
votes. Not in the slightest.
Yes, I am aware that B
is the most generally preferred candidate and that by voting for B C
supporters have also defeated A.
That is, in fact, the only thing they have done.
If a A and C voters
had not expressed a 2nd preference and voted
A would have won, or if two votes had been cast differently C would have
Sure, and in either scenario the losing faction says to themselves,
"why didn't I vote for B?" It can only help them, and can
never hurt them. Here, I'll show the decision matrix. The top
row is the vote of the A supporters, and the left column is the votes of
the C supporters. The corresponding matrix entry is who wins the
election. (This may look lousy, but if you cut and paste into
something that has monotype spacing it will look fine):
----| A | A>B |
C | A | A |
C>B | B | B |
Now, if C happens to have more first place support than A, the
matrix in stead looks like this:
----| A | A>B |
C | C | B |
C>B | C | B |
Now, lets combine the two matrices and show what the possibilities
for each faction are. The result for each faction if A has
more votes are before the slash, and after the slash is if C has more
----| A | A>B |
C | A/C | A/B |
C>B | B/C | B/B |
So, for the A faction, voting their full preferences changes the
result from C winning to B winning, or keeps the result the same.
Similarly, for the C faction, voting their full preferences changes the
result from A winning to B winning, or keeps the result the same.
Voting a second preference will NEVER cause an adverse result for a
faction in this election.