Multicandidate elections: Aggregate uncertainty in the laboratory

Abstract

The rational-voter model is often criticized on the grounds that two of its central predictions (the paradox of voting and Duverger's Law) are at odds with reality. Recent theoretical advances suggest that these empirically unsound predictions might be an artifact of an (arguably unrealistic) assumption: the absence of aggregate uncertainty about the distribution of preferences in the electorate. In this paper, we propose direct empirical evidence of the effect of aggregate uncertainty in multicandidate elections. Adopting a theory-based experimental approach, we explore whether aggregate uncertainty indeed favors the emergence of non-Duverger's law equilibria in plurality elections. Our experimental results support the main theoretical predictions: sincere voting is a predominant strategy under aggregate uncertainty, whereas without aggregate uncertainty, voters massively coordinate their votes behind one candidate, who wins almost surely.

Voting in Three-Alternative Committees: An Experiment

“…Bouton et al [6] and Bouton et al [7] are the first to hint at the fact that experimental elections with three alternatives may be different in that respect, but their underlying model is not quite the same as ours and so their findings do not really answer our question. The attention of the former paper is on comparing the efficiency of approval voting versus the simple plurality rule and the latter investigates Duverger's Law.…”

“…Treatment 3 was chosen such that posterior probabilities for a type a voter were "in favor" of voting for alternative A. When considering voting for her type, type a faced the same pivotal probabilities as in treatment 2, so a voter voting for A found herself most likely pivotal in states b and c. 6 In this treatment, posterior probabilities and pivotal probabilities gave conflicting information and the differences in pivotal probabilities by far outweigh the differences in posterior probabilities. A naive voter using only posterior probabilities may vote for A exclusively in this treatment.…”

“…First, a set of instructions was read aloud while participants read along. Instructions (see Appendix C) were handed out as hard copies so that 6 When type a considers voting for her type, pivotal probabilities were the same in treatments 2 and 3 because type distributions are the same in both treatments. Pivotal probabilities depend on the probabilities with which a random voter votes for a certain alternative, which are equal to type distributions when voters vote for their types.…”

Expressive Voting and Its Cost: Evidence From Runoffs With Two or Three Candidates

“…While the third candidate never ranks first or second in samples 3 and 4, we cannot entirely exclude that some voters thought ex ante that she had a nonzero probability of winning. However, Bouton, Castanheira, and Llorente‐Saguer () showed that the sincere equilibrium also requires that voters give a sufficiently large probability to the existence of a state of nature where the third candidate has a stronger support than one of the top two, or that they give a positive probability to a full reversal of support between the third and the candidate ideologically closest. Both conditions seem unlikely to be satisfied when the third candidate lags far behind the top two in the first round.…”

Unanimous Rules in the Laboratory

“…In this case, the right decision is simply the one that corresponds to the majority of signals. 8 In our context, a responsive pro…le is such that (i) at least some common value agents play action b with positive probability, and (ii) not all of them play b with probability 1. This ensures that, in equilibrium, some pivot probabilities are strictly positive -agents a¤ect the outcome of the vote with positive probability.…”