Some regrettable grading scale effects under different versions of evaluative voting

Résumé En

Many voters seem to appreciate the greater freedom of expression afforded by alternative voting rules; in evaluative voting, for example, longer grading scales and/or negative grades seem desirable in so far as, all other things being equal, they allow greater expressivity. The paper studies to what extent the behavior of voters, and the outcomes of elections, are sensitive to the grading scale employed in evaluative (or “range”) voting. To this end, we use voting data from an experiment conducted in parallel with the 2017 French presidential election,which aimed to scrutinize the negative grade effect and the length effect in grading scales. First, this paper confirms that the introduction of a negative grade disfavors “polarizing” candidates, those whose political discourse provokes divisive debate, but more generally we establish that it disfavors major candidates and favors minor candidates. Second, under non-negative scales, polarizing candidates may be relatively disfavored by longer scales, especially compared with candidates who attract only infrequent media coverage and who are little known among voters. Third, longer scales assign different weights to the votes of otherwise equal voters, depending on their propensity to vote strategically. Overall, we observe that the benefits of the expressivity provided by longer scales or negative grades need to be balanced against the controversial advantage these give to minor candidates, and their tendency to undermine the principle that each vote should count equally in the outcome of the election.