The 2002 French Approval Voting study

The largest study contrasting approval voting with plurality voting in an important actual election was for the French Presidential Election (non-runoff round) of 2002. Here is an abbreviated English-language version of their paper:

Jean-Francois Laslier & Karine Vander Straeten: Approval Voting: An Experiment during the French 2002 Presidential Election (and local copy). And the full French-language version is #2003-007 here (or see local copy) and here's what seems to be a French-language pdf slideshow on this. And here's an English-language paper (2009 pdf).

They conducted an approval-voting pseudo-election in parallel with the genuine French (plurality-style) election, using several thousand voters, all of whom were also actual voters in the real election. Here are their results (listed in order of finish in the official plurality election).

2002 results: # Candidate Approval Finished(AV) Plurality 1 Chirac 36.7% 1 19.9% 2 Le Pen 25.1% 4 16.9% 3 Jospin 32.9% 2 16.2% 4 Bayrou 27.1% 3 6.8% 5 Laguiller 16.8% 9 5.7% 6 Chevenement 22.4% 6 5.3% 7 Mamere 24.3% 5 5.2% 8 Besancenot 17.6% 8 4.2% 9 Saint-Josse 13.5% 11 4.2% 10 Madelin 20.4% 7 3.9% 11 Hue 11.3% 14 3.4% 12 Megret 13.8% 10 2.3% 13 Taubira 12.6% 13 2.3% 14 Lepage 13.4% 12 1.9% 15 Boutin 6.7% 15 1.2% 16 Gluckstein 5.5% 16 0.4% (Total) 315% 100%

As you can see, with Approval Voting the election results – not only the top two, but in fact all the way down the line – would have been dramatically different. This illustrates the tremendous distortions caused by strategic-voting effects, "vote-splitting" effects, and "cloned candidate" effects with plurality voting; such bad effects tend to be even more shriekingly obvious in elections like this one (we expect similar effects in the Iowa 2008 Presidential Caucuses) which include many viable candidates.

Under the French rules this (plurality) election was close enough that by law, a second "runoff" election needed to be held between the top two plurality finishers Chirac and Le Pen. The fact that Plurality (in the election above) had produced a tremendously distorted result ranking Chirac and Le Pen as "close," was proven by the fact that in the runoff, Chirac beat Le Pen by an enormous margin of 82.2% to 17.8% (far greater than the largest landslide ever in any US presidential election, which was only about 60%). As you can see, even Approval Voting's (less distorted) results still were somewhat distorted as far as what you might have expected about Chirac versus Le Pen is concerned. That appears to be because of "strategic approval voting" where most voters approved just one of {Jospin, Chirac} not both, figuring since they were going to be the top two, it was best to thus-maximize their vote's "impact." (See, e.g, the "Matrice des associations" in the paper for data backing that sort of contention up – only 15 out of 2587 voters approved both Chirac and Jospin.)

Probably Range Voting would have behaved better in that respect since with range voting voters would have had the option of being "more honest" in their vote. For example, a range voter (using 0-to-99 score range) who scored Chirac=99, Jospin=83, would with approval voting be "strategically forced" to approve Chirac but not Jospin in order to have nonzero impact on the Chirac-vs-Jospin battle. With range voting, an honest vote would have an impact on this battle; with approval voting, it would have zero. Also with range voting, a voter could distort her vote (e.g. Chirac=99, Jospin=60) to get more impact than a fully-honest vote, but more honesty than a fully-strategic vote. That kind of partly strategic, partly honest vote is possible with range but not with approval voting.

Another interesting point is that, even with approval voting, no candidate got more than 37% Approval. Keep that in mind as a counterexample in case somebody claims that "obviously" some candidate will get more than 50% Approval. Voters are not necessarily happy about their choices – and whenever that is so, it will clearly be seen with approval voting.

If the French 2002 election had been held with Approval Voting, the top two instead would have been Chirac versus Jospin, and quite plausibly the popular former PM Jospin (who suffered a lot of vote-splitting in the above election) would have won that runoff, changing history.

Pre-election polls had shown that a hypothetical Jospin-Chirac runoff (which was expected – Chirac vs Le Pen was a big surprise) would be too close to call, but it was clear Le Pen would lose big in a runoff with either. Jospin may have had a slight edge over Chirac: In their last 12 predictions – late February to the election – the TNS-Sofres polls about a hypothetical Jospin-vs-Chirac runoff showed Jospin winning 8 times, Chirac 2 times, and a tie twice (suggesting Jospin's chances were 9/12=75%). However, Chirac supporters could counter that among the last 4 polls, Chirac won 2 and tied 2, suggesting Chirac's chances were 75%! Within the full set of 25 Sofres polls Chirac won 8 and Jospin 12, with 5 tied, which would suggest Jospin's chances were 14.5/25=58%, which is also about what you get if you take an weighted average of all the 25 polls weighting the more-recent ones heavier, hence is my best guess.

The reason Jospin would have done better in a runoff versus Chirac than he did in the first round was that Taubira's and Chevenement's first-round voters generally preferred Jospin>Chirac.

A strategic ploy which probably both happened and worked: Another interesting possibility is that some Chirac voters may have intentionally voted for Le Pen figuring that way Chirac would beat Le Pen in the runoff, whereas Chirac was much less likely to defeat Jospin in the runoff. Think that's unlikely? Wrong: In the 2007 French election 10-31% of voters of various types admitted, when asked by the TNS-Sofres polling agency, that they strategically lied in their first-round vote; in 2012 this percentage was 20. If so, the 2002 election was a case where voting for the worst candidate in that voter's view, was actually superior strategy to voting for her best choice. My personal estimate/guess is this strategy was used, and did succeed in keeping Jospin out of the runoff, and more probably than not Jospin would have won that runoff. In other words, my best guess is this strategy was used, and actually worked. That's an example of one common runoff pathology which never arises with (single round) approval and range voting.

German approval-voting studies 2008-2009
French 2007 range-voting study
French 2007 multi-voting-method comparison multi-study
French 2012 election, approval & other methods
France 2000+
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