Beliefs and Voting Decisions: A Test of the Pivotal Voter Model

We report results from a laboratory experiment that provides the first direct test of the pivotal voter model. This model predicts that voters will rationally choose to vote only if their expected benefit from voting outweighs the cost. The expected benefit calculation involves the use of the voter’s subjective probability that s/he will be pivotal to the election outcome; this probability is typically unobservable. In one of our experimental treatments we elicit these subjective probabilities using a proper scoring rule that induces truthful revelation of beliefs. The cost of voting and the payoff to the election winner are known constants, so the subjective probabilities allow us to directly test the pivotal voter model. We find some support for the model: While a higher subjective probability of being pivotal does increase the likelihood that an individual chooses to vote, the decisiveness probability thresholds used by subjects are not as crisp as the theory would predict. We find some evidence that individuals learn over time to adjust their probabilities of being pivotal so that they are more consistent with the historical frequency of decisiveness, although such learning appears slow; many subjects\' assessments of their pivotalness remain substantially higher than is warranted by the electoral history.