Condorcet efficiency of positional voting rules with single-peaked preferences

A discussion is presented regarding the single-stage election procedures Plurality, Negative Plurality, and Borda Rules; with an emphasis on their Condorcet Efficiency, which measures their propensity to elect the Condorcet Winner. A theoretical analysis shows how the Condorcet Efficiency of these voting rules change as the various measures of group mutual coherence change. Both Plurality and Negative Plurality Rules are found to perform very poorly over identifiable ranges of the defined measures of group mutual coherence. While Borda Rule is not always found to be the most Condorcet Efficient single-stage rule in all scenarios, it never performs poorly under any scenario. These theoretical results are then reinforced by empirically-based analysis to show very solid support for using Borda Rule, despite some concerns that have been expressed that Borda Rule requires voters to rank candidates, while Plurality and Negative Plurality Rules do not.

The standard two-stage voting rules Plurality Elimination and Negative Plurality Elimination are evaluated relative to Borda Rule on the basis of Condorcet Efficiency. Theoretical analysis shows that the Condorcet Efficiency of these two-stage voting rules consistently marginally dominate Borda Rule as the various measures of group mutual coherence change. However, it is also found that the probability that either of the two-stage rules will elect a different candidate than the winner by Borda Rule is quite small. Empirically-based analysis reinforces this observation to lead to the general conclusion that the additional effort that is required to use a two-stage voting rule, rather than simply using Borda Rule, is not likely to be worthwhile. Other benefits are considered that result from using Borda Rule rather than a two-stage voting rule.

A resource available in different types is to be distributed or redistributed among agents differing in their ability to consume these types. Preferences over consumption levels are not observable but known to be single-peaked. We identify the only strategy-proof and efficient allocation rule satisfying a formulation of “fair net trades” (Schmeidler and Vind in Econometrica 40(4):637–642, 1972). This rule coincides with the “generalized uniform rule” (Thomson in Axiomatic analysis of generalized economies with single-peaked preferences, 1995a) when the resource is available in a single type and with the “egalitarian rule” (Bochet et al. in J Econ Theory 148:535–562, 2013) when there are no individual endowments. Moreover, it coincides with the “uniform rule” (Sprumont in Econometrica 59(2):509–519, 1991) when the resource is available in a single type and there are no individual endowments. This rule belongs to a new class of group strategy-proof rules. Our analysis provides a unified treatment of the applications in Bochet et al. (Theor Econ 7:395–423, 2012, J Econ Theory 148:535–562, 2013).

We use preference data from the 2015 parliament election in the Austrian federal state of Styria to analyze different voting rules. An exit poll right after the election collected data on ordinal and cardinal preferences from approximately 1000 actual voters. Our analysis is threefold. First, we determine the hypothetical social outcomes under different voting rules; second, we investigate the stability of the outcomes under those rules. Finally, we provide a categorization of different types of parties and analyze the impact of certain voting rules (Plurality Rule, Plurality Run Off, Hare System, Condorcet Method, Approval Voting, Borda Rule, Evaluative Voting, and Majority Judgment) on the performances of parties in those scenarios.

This paper combines social choice theory with mathematical optimization by applying various group decision concepts to a classical problem of combinatorial optimization, namely the famous traveling salesperson (sales- man) problem. The aim of the latter is to find a tour through all vertices of a given graph along edges of minimal total cost. In this contribution we replace the measure of additive edge costs by the social acceptance of different edges and the resulting tours. In particular, for four different voting rules, the Borda rule, Approval voting, Plurality rule and Simple Majority rule, we will investi- gate the social acceptance of tours derived from global and local decisions. It will be shown that these two decision approaches can lead to widely varying results.

We compare the Condorcet Efficiencies of the plurality rule, the negative plurality rule, and the Borda rule to examine what might be gained by using a voting rule that requires candidate rankings. Previous analyses have considered (1) voting situations for which the three rules determine different candidates as winners (and the Condorcet Efficiencies might actually differ across the three rules) as well as (2) refined measures of Group Mutual Coherence that assess the presence of underlying models of rational behavior that governs voter preferences. In this paper, we present the final step of this particular line of analysis by analyzing (1) and (2) simultaneously. We conclude that there is a considerable benefit on the basis of Condorcet Efficiency from asking voters to submit candidate rankings in three-candidate elections.

In collective decision making, where a voting rule is used to take a\ncollective decision among a group of agents, manipulation by one or more agents\nis usually considered negative behavior to be avoided, or at least to be made\ncomputationally difficult for the agents to perform. However, there are\nscenarios in which a restricted form of manipulation can instead be beneficial.\nIn this paper we consider the iterative version of several voting rules, where\nat each step one agent is allowed to manipulate by modifying his ballot\naccording to a set of restricted manipulation moves which are computationally\neasy and require little information to be performed. We prove convergence of\niterative voting rules when restricted manipulation is allowed, and we present\nexperiments showing that most iterative voting rules have a higher Condorcet\nefficiency than their non-iterative version.\n

Asymptotics of the minimum manipulating coalition size for positional voting rules under impartial culture behaviour

The Condorcet efficiency of Borda Rule with anonymous voters

On the Constitutional Choice of a Democratic Voting Rule: An Experimental Approach

The Borda Compromise states that, if one has to choose among five popular voting rules that are not Condorcet consistent, one should always give preference to the Borda rule over the four other rules. We assess the theoretical as well as the empirical support for the Borda Compromise. We find that, despite considerable differences between the properties of the theoretical framework and the characteristics of two sets of observed ranking data, all three analyses provide considerable support for the Borda Compromise.