Sunday, March 15, 2009

Burlington Instant Runoff Election riddled with pathologies

The instant runoff election in Burlington,Vermont suffered from nearly every pathology in the book: Non monotonicity - where with instant runoff, a voter can hurt their preferred candidate by ranking them first. A spoiler effect - in this election, Kurt Wright was the spoiler. The "no show" paradox - Wright supporters who also supported Montrol would have helped him if they hadn't shown up to vote at all. Majority failure -the candidate supported by the most voters did not win. Incumbent protection thanks to name recognition. Centrally counted votes - instant runoff opened up the election to fraud because votes were not counted where cast.

Instant runoff voting helped Burlington incumbent Bob Kiss win by getting the most 3rd choice votes. Opponent Kurt Wright had the most 1st and 2nd choice votes but lost the election.

Election method experts have issued a report that shows the bizarre pathologies in the Burlington instant runoff election. Here are some excerpts:

Burlington Vermont 2009 IRV mayor election
Thwarted-majority, non-monotonicity & other failures (oops)
By Anthony Gierzynski, Wes Hamilton, & Warren D. Smith,
March 2009. (skip to summary)

The pathologies

1. According to the pairwise table, Democrat Andy Montroll was favored over Republican Kurt Wright 56% to 44% (930-vote margin) and over Progressive Bob Kiss 54% to 46% (590-vote margin) majorities in both cases....

2. Despite that, IRV still seems to have performed better in this election than plain plurality voting, which (based on top-preference votes) would have elected Wright. That would have been even worse, since Wright actually was a "lose-to-all loser"....

3. Also, in this IRV election, Wright was a "spoiler"; if Wright had not been in the race then Montroll would have won (which the Wright voters would have preferred...

4. Another problem with IRV is the fact that it cannot be counted in precincts because there is no such thing as a "precinct subtotal." That's bad because it forces centralized (or at least centrally-directed) counting, thus making the election more vulnerable to fraud and communication outages....

5. ...this election also featured (what voting theorists call) a "no-show paradox." That is, if 753 Wright voters who favored Montroll over Kiss had simply stayed home and refused to vote, they would have gotten, in their view, a better election winner(Montroll) than they got by honestly voting....

6. Finally – and probably craziest of all – this election also featured nonmonotonicity.....In other words, Kiss won, but if 753 Wright-voters had switched their vote to Kiss, that would have made Kiss lose!

...pretty much every voting method mankind ever invented would elect MONTROLL
– making this a pretty easy election to call – except that IRV elects KISS and plurality elects WRIGHT.

...The truth

As shown in this election, IRV does not "solve the spoiler problem," does not"allow voters to vote their true preference without fear of inadvertently electing a candidate they cannot stand," and it does not elect candidates "actually preferred by a majority." These and other (e.g. non-monotonicity) pathologies are not rare. IRV in this election did not serve as a "bulwark of democracy" – rather the opposite. Our belief is that range voting, also known as "score voting," (and probably also approval voting) would not have exhibited any of these problems and in the present example would have elected Montroll. (Indeed range voting never exhibits non-monotonicity or spoilers, and it is rare that it refuses to elect beats-all winners.)

See the full report at the Center for Range Voting.