[EM] Why I think IRV isn't a serious alternative

[Brian Olson]

There's been a lot of discussion lately started by people who advocate  
IRV. I'm mystified. Really? You really think IRV is a good system?  
I've spent so long considering it to be pretty much junk that I really  
am confused by that position. Here's my summary of why I think IRV is  
junk.

(from http://bolson.org/voting/irv/ )


First, a concession
Yes, IRV is better than nothing. It's better than tired old pick-one  
voting. But that's about all it's better than...

IRV Gets Worse Results

The graph below shows an assortment of election methods run in  
simulated elections of 10000 voters and various number of candidates  
to choose from. Increased happiness is on the virtical axis. In  
general, as there are more choices, there's a better chance of there  
being some choice that makes more people happy, and so overall  
happiness rises. If you can only cast one vote this starts to fail  
above 7 choices as the populace gets fractured voting for their  
favorites. At the bottom is a control test experiment of picking a  
choice at random, which on average makes half the people happy, and  
half unhappy, for a total of zero.

Third from the bottom is Instant Runoff Voting. IRV doesn't get very  
good overall results because it only considers a small part of the  
votes at once, the top ranked choice. Because of this it can miss  
broadly supported compromise candidates. IRV doesn't benefit as much  
from having a wide selection of candidates to choose from. And as the  
next section shows, it can flat out get the wrong answer.



IRV Gets Chaotic

The diagrams below illustrate the decision reached by two election  
methods depending on where the center of public opinion lies. If the  
center of public opinion is closest to a candidate (diamonds) then the  
election should go to that candidate and the diagram gets colored to  
match. The plot of IRV results shows that IRV is capable of completely  
missing giving the election to the blue candidate even when the  
population is right there. In other regions the result is chaotic.

IRV has this irregular behavior because of how it transferrs lots of  
votes and disqualifies candidates. Subtle differences in the order of  
disqualification of candidates and the transfer of votes to other  
candidates can wind up swinging the election to substatntially  
different outcomes.

	
Instant Runoff Vote	Virtual Round Robin Election (Condorcet's Method)
more election diagrams
IRV Doesn't Scale Up

IRV requires all the ballots to be in one place at one time for  
counting (when someone's top active choice is disqualified, you have  
to go back and check their ballot to see how they would vote for their  
next most preferred). Or, for computer counting, the data from all the  
ballots has to be gathered in one computer. Hand counting techniques  
require physically moving piles of ballots around, and in a large  
election this could wind up requiring a fork lift.

VRR/Condorcet can be summed up from intermediate results, counted at  
precincts or counted by many people hand counting ballots. Hand  
counting techniques just need a sheet of paper to make tally marks on.

FUD: Other Methods Hurt Your Top Choice

The simplistic method of Instant Runoff Voting, always counting only  
your top ranked choice (of candidates not eliminated in the rounds so  
far), is philosophically attractive to some people, but may not  
actually best serve your interests. One way of thinking about how IRV  
works is that if you were to assign numeric ratings to your choices,  
you might give a 1 to your fourth choice, 10 to third, 100 to second  
and 1000 to your favorite. If this huge difference in preference  
between choices accurately represents how you feel, IRV may represent  
you relatively well (but it can still make the generally wrong choice,  
as shown above). Other methods tend to have a more uniform effective  
distribution of preference between the choices. A second or third  
choice obviously isn't as preferred as the first choice, but out of  
several candidates, second or third choice is probably still good or  
ok. IRV won't consider these lower ranked choices at all, and may have  
prematurely disqualified them if they didn't get enough first-choice  
vote.

There's a more general rumor applied to IRV and other rankings methods  
in general that says you should only vote for a top choice, or a top  
few, and not give any ranking to lower preference choices so that they  
will not be aided in any way. For any decent election method, and even  
IRV, your lower ranking choices will only be relevant if your higher  
ranking choices are losing anyway. Sometimes, that's just Democracy,  
and you don't get what you want. A fully ranked ballot at least gives  
you some say in which of the other ones gets elected. You might not  
get what you want, but you might get someone less bad than worst.

FUD: Other Methods Dilute Your Vote

Similar to the don't-fully-rank FUD above, this claims that there's a  
possibility of violating the 'one person one vote' principle of  
democracy. At the very least there is an equal potential for every  
voter to vote by fully filling out their ballot. There is an equal  
potential for everyone to vote now, and half the people don't cast any  
vote. It could be further considered that your 'vote' is not simply  
the traditional statement of who your favorite is, but a statement  
about all the choices. Suppose there are ten choices. With the old  
pick-one ballot, you get to vote YES on one choice and have to vote NO  
on the rest. With an approval ballot, you can vote YES on as many as  
you like. With a rankings ballot, you can vote 1st, 2nd, 3rd, etc. on  
the ones you like and leaving some blank means "I don't know" or "I  
don't care" - which is an expression about that choice. Everyone who  
shows up and votes is saying something about all the choices, and  
casting an equal weight ballot as anyone else. It's then important  
that the ballot be structured reasonably to get as much expression out  
of the voter as can easily be gotten, and it is important that the  
counting method use this data as best as possible so as to satisfy the  
will of the people.

Comments? Email me

back to bolson's voting page


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