The causal impact of ballot order on voting behaviour : evidence from a natural experiment in Italy

Abstract

The study of ballot design has gained salience in political science. The very procedure voters need to carry out in order to vote affects electoral outcomes, on top of the more direct effects of electoral rules. I focus on a specific channel through which such effects might realise: the order in which parties appear in the voting paper. Exploiting a natural experiment in the 2018 Italian general election, I estimate the electoral gain obtained by parties by virtue of being assigned the first (top-left) position in the voting paper. I use the fact that in Italy the party order in ballots is determined independently for the two elected chambers, thus exposing voters to two different exogenously determined lists. I find that, within a same municipality, parties which are assigned the first position in one chamber obtain a vote share between 0.1 and 0.2 p.p. higher relative to the other chamber. On average, this means that roughly 1 voter every 500 is influenced by the order in which party appears on the voting paper.