One Person, One Vote: Estimating the Prevalence of Double Voting in U.S. Presidential Elections

Beliefs about the incidence of voter fraud inform how people view the trade-off between electoral integrity and voter accessibility. To better inform such beliefs about the rate of double voting, we develop and apply a method to estimate how many people voted twice in the 2012 presidential election. We estimate that about one in 4,000 voters cast two ballots, although an audit suggests that the true rate may be lower due to small errors in electronic vote records. We corroborate our estimates and extend our analysis using data from a subset of states that share social security numbers, making it easier to quantify who may have voted twice. For this subset of states, we find that one suggested strategy to reduce double voting—removing the registration with an earlier registration date when two share the same name and birthdate—could impede approximately 300 legitimate votes for each double vote prevented.