COMMENTS ON TWO FORMS OF IRV

Instant Runoff Voting, as defined in proposed legislation in Vermont in 2002, and as used by most proponents of IRV, asks each voter to rank the candidates. Once all rankings have been made, the election procedure checks to see if anyone has a majority of the first-place votes. If not, the name of the candidate with the fewest first-place votes is crossed off each list and the election procedure again looks to see if anyone has a majority. The process is repeated until a majority is found—if there are only two candidates left, one will have a majority. (Yes, I’m ignoring the possibility of a tie.) That process is also known as Single Transferable Vote (STV).

In 2003 the proponents of IRV changed the system. If no candidate has a majority, all but the two with the greatest number of first-place votes are eliminated, and the system chooses the one of those two with the most first-place votes. I’ll call this system IRV 2003 and the other one IRV 2002. The stated reason for the change was “simplicity.”

IRV 2003 shares all the faults of IRV 2002, but has one more. Proponents of IRV note that one of the faults of Plurality voting is the case of spoilers. They argue, for example, that in Florida in 2000 Nader was a spoiler because he had no chance to win, but he took enough more votes from Gore than from Bush that Florida went for Bush instead of Gore. IRV 2002 is not directly affected by spoilers, because first-place votes for the potential spoiler are typically so few that that candidate gets eliminated early in the election procedure. In a four-candidate race, IRV 2003 is susceptible to spoilers. The following example illustrates the point (the notation is as we did it on the board in class):

3 30 32 35

A B C D

B A B B

C C D A

D D A C

Under IRV 2002 (which is the method we used in class), A is eliminated first, and then B has 33 first-place votes, so C is eliminated next, and B win over D 65 to 35. Under IRV 2003, both A and B are eliminated in favor of the C and D, which are the two highest vote getters. C beats D 65 to 35 even though. C is ranked below the median by 68 voters. If A had stayed out of the race, B would have had 33 first-place votes, and, under IRV 2003, C would have been eliminated, resulting in B’s winning. Thus by entering the race with no chance to win, A is a spoiler.