Incentivized choice in large-scale voting experiments

Survey experiments that investigate how voting procedures affect voting behavior and election outcomes use hypothetical questions and non-representative samples. We present here the results of a novel survey experiment that addresses both concerns. First, the winning party in our experiment receives a donation to its campaign funds inducing real consequences for voting. Second, we run an online experiment with a Dutch national representative sample (N = 1240). Our results validate previous findings using a representative sample, in particular that approval voting leads to a higher concentration in votes for smaller parties and strengthens centrist parties in comparison to plurality voting. Importantly, our results suggest that voting behavior is not affected by voting incentives and can be equally reliably elicited with hypothetical questions

Who is in Your Top Three? Optimizing Learning in Elections with Many Candidates

Elections and opinion polls often have many candidates, with the aim to either rank the candidates or identify a small set of winners according to voters' preferences. In practice, voters do not provide a full ranking; instead, each voter provides their favorite K candidates, potentially in ranked order. The election organizer must choose K and an aggregation rule. We provide a theoretical framework to make these choices. Each K-Approval or K-partial ranking mechanism (with a corresponding positional scoring rule) induces a learning rate for the speed at which the election correctly recovers the asymptotic outcome. Given the voter choice distribution, the election planner can thus identify the rate optimal mechanism. Earlier work in this area provides coarse order-of-magnitude guaranties which are not sufficient to make such choices. Our framework further resolves questions of when randomizing between multiple mechanisms may improve learning, for arbitrary voter noise models. Finally, we use data from 5 large participatory budgeting elections that we organized across several US cities, along with other ranking data, to demonstrate the utility of our methods. In particular, we find that historically such elections have set K too low and that picking the right mechanism can be the difference between identifying the ultimate winner with only a 80% probability or a 99.9% probability after 400 voters.Comment: To appear in HCOMP 201

Approval consensus measures

In many realistic group decision making problems where a “representative” collective output must be produced, it is relevant to measure how much consensus this solution conveys to the group. Many aspects influence the final decision in group decision making problems. Two key issues are the experts’ individual opinions and the methodology followed to compute such a final decision (aggregation operators, voting systems, etc.). In this paper we consider situations where each member of a population decides upon approving or not approving each of a set of options. The experts express their opinions in a dichotomous way, e.g., because they intend to use approval voting. In order to measure the consensus or cohesiveness that the expression of the individual preferences conveys we propose the concept of approval consensus measure (ACM), which does not refer to any priors of the agents like preferences or other decision-making processes. Then we give axiomatic characterizations of two generic classes of ACMs

What voting rules do citizens prefer?

Le système électoral fait de plus en plus objet de débats et de discussions au Canada et ailleurs dans le monde. Bien qu’il existe de nombreuses études sur les avantages et les inconvénients des différents systèmes électoraux, très peu d’entre elles examinent les préférences des citoyens concernant les modes de scrutin et plus particulièrement la façon dont les individus expriment leur choix sur le bulletin de vote. Dans le cadre de ce mémoire, je m’attarde aux questions suivantes : quelle façon de voter les citoyens préfèrent-ils et pourquoi ? Afin de répondre à ces questions, j'ai mené une expérience en laboratoire avec près de 200 participants dans le cadre des élections fédérales canadiennes de 2019. Les participants furent invités à voter dans une série d'élections en utilisant chacune des trois façons de voter suivantes en ordre aléatoire : scrutin à vote unique, vote par approbation et vote par rangement. Après chaque vote, les participants furent informés du résultat électoral dans leur groupe et interrogés sur leur niveau de satisfaction à l'égard de chaque façon de voter. Les résultats démontrent que les citoyens préfèrent avoir la possibilité de classer les partis plutôt que d'utiliser un scrutin à vote unique ou un vote par approbation. Les individus sont également plus susceptibles d’aimer un mode scrutin lorsqu'ils sont satisfaits des résultats de l’élection.Debates over which electoral system would best serve the general public are on the rise in Canada and in other democratic countries. Although there exists a rich literature on the benefits and shortcomings of different electoral systems, very few studies examine citizens’ preferences regarding voting rules and the ways in which individuals can cast their vote. In this paper, I address the following questions: What voting rules do citizens prefer and why? To address these questions, I conducted a within-subject laboratory experiment with nearly 200 participants in the run up to the 2019 Canadian federal election. Participants were asked to vote in a set of elections using each of the three following types of ballots in random order: one-mark ballot, approval voting and ranked voting. After each vote, participants were informed of the election results and asked about their level of satisfaction with each voting system. The results show that citizens prefer having the option to rank order the parties rather than using a one-mark ballot or approval voting. Individuals are also more likely to favour voting rules when they are satisfied with the results of the election

Under-representation in America: Special Interest Groups, Referendums, and Election Reform

Americans are inadequately represented. Despite being such an important part of political science, social choice theory remains an area of study seldomly incorporated into political dialogue. Special interest groups and gerrymandering insidiously affect political substructures and can have long-lasting impacts. Referendums often produce paradoxical results and frequently fail to satisfy voters. They can also restrict minority rights when political participation is in question. Voting systems around the world have remained unchanged for over two centuries and poorly express voter desires. Improving upon elements encompassed by social choice theory has the potential to ensure more accurate representation. The issue of gerrymandering can be mitigated using new identification and districting methods. Additionally, policy makers should take note that referendums are most useful with single issue topics. Lastly, voting systems like Majority Judgement offer to revolutionize the way voting is accomplished in America. This thesis showcases numerous correlations demonstrating representation shortfalls in each of these areas and details improvements where aspects of these elements can be improved

The problem of the divided majority: Preference aggregation under uncertainty

This paper reports on the results of a series of experimental laboratory elections. The novelty of the design allows me to study the extent to which voting methods defeat the Condorcet loser and elect the Condorcet winner in a repeated-game, divided majority setting. I assess and compare the performance of three voting mechanisms, Approval Voting, Borda Count, and Plurality Voting under two information structures. Voters either know the preference structure in the electorate or hold no information regarding other voters’ preferences. With enough experience, the number of elections won by the Condorcet loser is fairly low across voting methods and information structures. Approval Voting and Borda Count dissolve information imperfections efficiently and allow voters to implement the Condorcet winner, independently of the underlying information structure. The frequency with which the Condorcet winner is elected under Plurality Voting crucially depends on available information. When voters are uninformed about the preference structure in the electorate, Plurality Voting fails to implement the Condorcet winner. This is costly and decreases total welfare

The problem of the divided majority: Preference aggregation under uncertainty

This paper reports on the results of a series of experimental laboratory elections. The novelty of the design allows me to study the extent to which voting methods defeat the Condorcet loser and elect the Condorcet winner in a repeated-game, divided majority setting. I assess and compare the performance of three voting mechanisms, Approval Voting, Borda Count, and Plurality Voting under two information structures. Voters either know the preference structure in the electorate or hold no information regarding other voters’ preferences. With enough experience, the number of elections won by the Condorcet loser is fairly low across voting methods and information structures. Approval Voting and Borda Count dissolve information imperfect

Multi-Winner Voting with Approval Preferences

Approval-based committee (ABC) rules are voting rules that output a fixed-size subset of candidates, a so-called committee. ABC rules select committees based on dichotomous preferences, i.e., a voter either approves or disapproves a candidate. This simple type of preferences makes ABC rules widely suitable for practical use. In this book, we summarize the current understanding of ABC rules from the viewpoint of computational social choice. The main focus is on axiomatic analysis, algorithmic results, and relevant applications.Comment: This is a draft of the upcoming book "Multi-Winner Voting with Approval Preferences

Two field experiments on approval voting in Germany

We report on two field experiments on Approval Voting conducted during actual state and federal elections in Germany. Voters provided approval ballots both for named district candidates and for state parties. The data reveal significant discrepancies in the outcomes under the official method and Approval Voting. Further, our analysis suggests that currently used voting methods do a poor job of representing the electorate’s preferences. As a consequence, some recurring features of the political landscape in a given country might be, in part, an artifice of the employed voting method