2003-08-03 23:32:35 UTC
I am interested in knowing how everyone here feels about this question:
Which is better, IRV or Plurality?
I highly doubt that this is the first time that this has been discussed
on the list, and I doubt that it will be the last. Nevertheless, I would
like to know what people have to say about it.
The reason I think that this question is important is because it has
immediate relevance for the election methods movement, if there is to be
one. That is, do the IRV people, Approval people, and Condorcet people
necessarily have to be blood enemies, or can they find a common ground in
their critique of plurality?
Personally, I am hoping that we can find a common ground, because I fail
to see how the movement could make much progress if it is so sharply
divided against itself this early in the game.
I will try to start off the discussion with some of my own thoughts.
First of all, there are two basic categories of discussion: One is the
technical evaluation of IRV versus Plurality, that is simply which one is
a more desirable voting system, leaving all other possible systems aside.
The other category deals more with the practical context. What are the
possible benefits or pitfalls of IRV advocacy? What is the relationship
between advocacy of IRV and advocacy for other, more desirable, systems?
(I assume that most people reading this know that I prefer Condorcet's
method to IRV.)
PART ONE: TECHNICAL EVALUATION OF IRV VS. PLURALITY, LEAVING OTHER METHODS
First, the technical side. To summarize, it seems to me that, all else
aside, IRV is a substantially better voting system then plurality.
To begin, let's assume an American-style two-party system as a starting
point. Unlike plurality, IRV allows people to vote for third party
candidates for their early choices, and still have the full power of their
vote to help decide between the two major party candidates, assuming that
the third party candidates are eliminated.
This is something in and of itself, because in many circumstances it
allows people to vote their conscience without casting a vote that is
irrelevant to the actual winner. This will allow people to get a somewhat
more realistic idea of what kind of support third parties have, and it
should add depth to political debates. It will also allow third parties to
run genuine campaigns without being demonized as spoilers, which would be
a pretty significant step towards eroding the two-party duopoly.
So, IRV works well when only two candidates are serious contenders.(In
those cases, it should always select the Condorcet winner.) However, when
there are three or more serious candidates, IRV can get somewhat chaotic.
Therefore, it may tend towards fairly binary political divisions, as does
Also, IRV does not allow a smooth transition from a given set of two
major contenders to an alternate set, because any party attempting to
replace a current member of the dominant pair set may have to pass through
a stage where they stand a good chance of throwing the race to the other
member of the pair set, thus going against the will of their would-be
This danger can be avoided if the supporters of the original pair set
member rank the replacement party second over the other pair set member in
sufficient number. Also, it can be avoided if the other pair set member is
As far as far-wing candidates go, far left Naderish candidates for
example, they would have a lot of trouble winning under IRV, because even
if they did manage to eliminate the Democrat, they would throw the race to
the Republican unless nearly all of the Democratic voters ranked the
Naderish candidate above the Republican. Of course, any far-wing candidate
would have trouble winning with Condorcet as well, but the difference is
that IRV offers a very strong incentive for voters to betray a favorite
far wing candidate if there is a danger that s/he might eliminate the
compromise candidate and throw the race to the other side.
As a result, the benefit of IRV in providing a clearer impression of
support for third parties should begin to falter at this point.
Nevertheless, if the support does reach this point, then that is a pretty
strong message in itself.
Also, this barrier of one party trying to take the place of another as a
member of the duopoly, while it is still quite steep under IRV, is not
nearly as steep as using plurality. That is, using plurality, third party
candidates have to build up their support from zero under the constant
adversity of being labeled a spoiler, and under the constant ambivalence
of voters as to whether to stick with the lesser of two evils. With IRV,
at least third parties can build up a reasonable-sized support base before
the second-order spoiler effect comes into play, and therefore they can
get themselves within 'striking distance' of one of the major parties
while still under the umbrella of non-spoilerhood.
A centrist candidate may be less likely to cause the same kinds of
problems using IRV as a far-wing candidate might cause. That is, a
candidate who is ranked second by nearly all of one wing party's voters,
or ranked second by a good portion of both wing party's voters. If such a
candidate manages to eliminate one of the major party candidates, then
they have a much better shot at winning the whole race than a Naderish
candidate would. Still, of course, a centrist candidate has a much steeper
hill to climb using IRV than using Condorcet.
To its credit, IRV never gives strategy incentives for truncation, unlike
Condorcet, although of course it does more frequently offer incentives for
favorite betrayal and order-reversal in general. Still, that is an
attractive anti-strategy measure, that later choices in IRV can never
either help or harm earlier choices. (Approval also fails on this measure,
if you translate it as the fact that adding a sincerely lower-preference
candidate to your list of Approved candidates can cause a sincerely higher
preference candidate to lose.)
In general, IRV has significantly better Condorcet efficiency than
If accurate polling data is available, it is possible that strategic
voting will lead to Condorcet-like results, although at the expense of
favorite betrayal, and possibly some nasty strategizing within the polls.
In contrast to plurality, IRV allows for ranked ballots. This allows
voters to communicate in much more detail than on a plurality (or
Approval) ballot, which is in general a good thing, although admittedly
voters may either vote strategically, thus distorting their communication,
or regret their choices later.
In response to an earlier post of mine, in which I said that I believed
that Approval, IRV, and Condorcet were all superior to plurality, Eric
Gorr wrote: "For me to believe a voting system to be worthy of any
consideration, it must at least be monotonic and IRV certainly is not."
That is certainly a good point, and I found it thought provoking. There
is no getting around the fact that IRV is non-monotonic, but I am not
entirely sure how devastating this would be for public elections.
One point that I would like to make is that, in practice, two round
runoff is not monotonic either.
For example, let's say that there is an election where there in one
dominant candidate on the right wing, and a few candidates competing in
the first round for the left. If your favorite candidate is the right wing
candidate, and you are fairly confident that s/he will make it to the
second round, you can use your first round vote to vote for a candidate on
the left who would be unlikely to win the second round, which could in
turn cause your sincere favorite to win, where s/he would have lost had
you voted for him/her in the first round, and let a more electable left
wing candidate into the runoff.
This is in effect a violation of monotonicity, because not voting your
sincere favorite for your first round choice can cause them to win where
they would have lost otherwise.
(Actually, there is more possibility for strategic manipulation in the
actual runoff than in IRV, because at least in IRV insincere votes can't
count for the voter's sincere favorite until after their phony favorite is
eliminated. That is, in the two round case I imagined above, you could
vote for your true favorite even if your phony favorite made it to the
next round, which is something you can't do in IRV.)
Of course, this comparison does not absolve IRV of its monotonicity
failure, but it does sort of put it in a larger context, as far as the
extent to which a non-monotonic method can be functional.
To illustrate the relative use of these methods, the single winner
systems that are used on a national level are 1. plurality (used in 68
countries with a total population of 1,849 million), 2. two round runoff
(used in 31 countries with a total population of 427 million), and 3. IRV
/ the Alternative Vote (used in two countries with a total population of
18 million). (My source is the International IDEA Handbook, and I think
that it is measuring only by what method countries use to elect their
lower house.) My point isn't that widely used systems are good; I'm just
pointing out that the two round system is not some obscure bogey system
that has been cast out of use because of its monotonicity failure.
I'm not quite sure what people on the list think about two round runoff,
but I've always assumed that it is a marginal improvement over plurality,
the cost of the second election aside. IRV, as far as I can tell, is not
very different from runoff in its basic operation, strategy, flaws, etc.
It seems to me that IRV is marginally better than two round runoff because
it allows for multiple rounds. (Also, in public elections, it is likely to
lead to higher voter turnout, etc.)
Anyway, my point is that while monotonicity is a valuable criteria, I
certainly don't think that it is all-important.
PART TWO: CONCERNS RELATING TO IMPLIMENTATION OF OTHER METHODS
So, I don't think that there is much ambiguity about the technical
superiority of IRV to plurality, however marginal some might argue it is.
What is more uncertain for me is the relationship between IRV advocacy
and the advent of other systems that are more effective, especially
Condorcet, STV, and CPO-STV.
Of course, IRV may also help lead toward STV, which I think would be a
good thing in itself. I imagine that this is a part of the reason that the
Center for Voting and Democracy decided to advocate IRV in the first
place, seeing as they started off as PR advocates with STV as their
favorite method. (The original name of the organization was "Citizens for
That is, of course, being familiar with IRV makes STV much, much easier
to understand, as they are essentially the same system.
Also, there is a chance that IRV may lead to Condorcet's method in the
That is, that advocacy for IRV and use of IRV can introduce many of the
relevant concepts to voters that they will need in order to better
IRV introduces people to the idea of ranked ballots, of course. It
introduces people to the idea that people's second and third choice votes
can have the same weight as their first choice votes, yet their voting
power is still essentially only one vote strong.
Also, IRV advocacy introduces a critique of the plurality system that
also provides the justification for Condorcet's method. It works to show
people that the composition of government is contingent on the voting
system, and it will help wake people up to the fact that they could have a
change in government through a change in the voting system.
Basically, IRV advocacy makes promises which in fact are fulfilled better
by Condorcet's method than by IRV, such as ending the spoiler effect. By
convincing people that it is important to end the spoiler effect, IRV
proponents are perhaps advocating Condorcet more than they are advocating
IRV, at least in the long run.
I know that I heard of IRV before I heard of Condorcet's method.
Understanding both the benefits of IRV and the flaws that remain in IRV
was what enabled me to appreciate Condorcet's method.
If IRV does become widely used, then third parties will at least have a
marginally greater chance to participate in politics. They will be more
likely to be eligible for matching grants, access to debates, etc.
Hopefully this will smash the myth that the votes that third parties have
been getting under the plurality system are indicative of their true
support; that is if they start gaining more votes, it will be clear that
the voting system was holding them back. This is obvious to most election
methods fans, but most Americans probably do not think of it this way.
Perhaps if, after making big gains, their support reaches a second
stagnant equilibrium at the point just before they cause a major party
candidate to get eliminated, it will be fairly obvious that IRV is at
fault, and a move to Condorcet will seem natural (at least to the third
Alternately, if people do vote honestly under IRV, and a big second-order
spoiler effect occurs, then the flaw in IRV will be completely transparent
to any commentator, and this could also provide a very clear opportunity
for Condorcet to come to the fore.
Ironically, the fact that IRV isn't as radical as Condorcet in
undermining two-party dominance could conceivably be a benefit in
practical terms (although it is an obvious drawback in normative terms).
IRV gives third parties less power to upset an otherwise winning democrat
or republican, which I think that many democrats and republicans actually
would appreciate. If the mainstream politicians do accept IRV, though,
alternative election methods have a pretty big foot in the door, in terms
of public awareness, etc.
Okay, those are some of the more hopeful appraisals of the relationship
between IRV advocacy and Condorcet advocacy. Now I will list a few of my
worries on the subject, about how IRV could possibly do more harm than
One worry is that IRV could help to further legitimize the two-party
system and absorb the momentum needed for deeper reform.
That is, it is possible that we may all get behind IRV, and it has a
great success, but then it gets 'locked in place,' and the power to make
any changes to is taken above our reach for an extremely long period of
Also, it may be possible for the powers that be to use the flaws in IRV
to bury all voting systems reform for an extremely long period of time.
For example, IRV could get fairly big, and then a major second-order
spoiler event could occur, people could be appalled, and the two-party
establishment people could take it as an opportunity to say "See, ranked
ballot voting is nonsense. Just ask Arrow. Case closed." And then go back
to plurality for an extremely long period of time. If anyone brings up
alternative voting methods, they can just say, "Don't you remember? We
tried changing the voting system and it backfired; forget about it."
Also, I'm not sure whether anyone is doing it on purpose, but we have a
real problem if IRV advocates are strawmanning Condorcet or Approval. Even
if the intentions are good, this cannot be justified.
The argument that voting systems people should wait under IRV is fully
entrenched before even bringing up alternatives does not hold water. First
of all, that could well be a very long time, quite possibly forever, and
in the meantime, there is a lot of benefit that can be had in using
Condorcet's method for purposes other than elections for representative
government. There is no sense in holding back that benefit to keep people
from questioning the idea that IRV is the best.
Along the same lines, if IRV people actually devote effort to making
Condorcet invisible, this is also unjustifiable. IRV people have no
responsibility to devote effort to promoting Condorcet, if they don't feel
like it, but there is no sense in their trying to 'keep Condorcet down.'
Again, I have no idea if anyone is actually doing this, but I think that
it is a problem if they are.
Of course, I think that this cuts both ways. I don't think that anyone
should present straw man arguments against IRV, and I don't think that
anyone should try to keep IRV out of the discussion.
In general, I think that it is very counter-productive for advocates of
Condorcet and Approval to spend their efforts trying to block attempts to
implement IRV. It seems obvious that their effort would be better spent
trying to implement their own favorite system, rather than defending
plurality against IRV.
This is a very big country, and there are lots of people who use voting
to decide things, and most of those people are still using plurality. Use
of IRV hardly means blocking Condorcet. 99% of the time, it means
overturning plurality or two round runoff.
Perhaps when we are deciding on which method to use to elect the
president, this will no longer be the case, but we are quite a long way
off that point, and for now the field is wide open.
It seems to me that there is tons of room for people to implement IRV in
some places, Condorcet in others, Approval in others, and still more
systems in others. Not only is this the most cooperative approach for the
movement to take, it is also the one that provides for the most feedback.
That is, if many groups are using each of the different methods, then
voting methods organizers will be able to track the results and see how
the different methods are working under different circumstances, and this
will enrich the theoretical debate immensely.
I have presented some of my opinions here. Although I am uncertain about
some things, I feel fairly sure about others. I am fairly sure that IRV is
technically better than plurality. I am fairly sure that IRV, Condorcet,
and Approval people should try to treat each other as allies rather than
competitors, and that they should not try to strawman or exclude each
I think that the voting methods movement will be healthier given a
pluralistic, multi-system approach, that is one in which different
alternative systems are being advocated for and implemented
simultaneously. I don't think that we should try to close off debate and
resolve on a single system before we begin advocacy. I think that we
should give people a chance to make intelligent decisions about voting
systems, rather than only letting them know about the system that we like
best. Of course, if they only ask for one recommendation, then we should
give them the one we prefer. But if they are interested in the
alternatives, then we should not hide them or give false arguments against
Election-methods mailing list - see http://electorama.com/em for list info