An earlier version of the article included a number of mistakes introduced during copyediting, including in particular the following: Throughout Section 2, all occurrences of the letters A and A′ had been incorrectly displayed as A and A′, respectively, thereby introducing ambiguity between profiles of ballots and individual ballots. Item [7] in the list of references (the book edited by Brandt et al.) had been replaced by a chapter within that book (and that chapter in turn had been attributed to the wrong author). Several references to items in the bibliography had been displayed incorrectly (omitting the names of authors). Throughout Section 2, all occurrences of the letters A and A′ had been incorrectly displayed as A and A′, respectively, thereby introducing ambiguity between profiles of ballots and individual ballots. Item [7] in the list of references (the book edited by Brandt et al.) had been replaced by a chapter within that book (and that chapter in turn had been attributed to the wrong author). Several references to items in the bibliography had been displayed incorrectly (omitting the names of authors). The original article has been corrected.