Dimitrios Xefteris

Candidate quality in a downsian model with a continuous policy space

This paper characterizes a unique mixed strategy Nash equilibrium in a one-dimensional Downsian model of two-candidate elections with a continuous policy space, where candidates are office motivated and one candidate enjoys a non-policy advantage over the other candidate. We show that if votersʼ utility functions are concave and the median voter ideal point is drawn from a unimodal distribution, there is a mixed strategy Nash equilibrium where the advantaged candidate chooses the ideal point of the expected median voter with probability one and the disadvantaged candidate uses a mixed strategy that is symmetric around it. Existence conditions require the variance of the distribution to be small enough relative to the size of the advantage.

Mixed strategy equilibrium in a Downsian model with a favored candidate: A comment

This note complements Aragones and Palfrey (2002) [2] by providing upper and lower bounds of the equilibrium payoff of the advantaged (disadvantaged) candidate for any symmetric distribution of the median voterʼs ideal policy and any (even or odd) number of equidistant locations. These bounds point to a negative (positive) relationship between the equilibrium payoff of the (dis)advantaged candidate and the uncertainty regarding the median voterʼs preferences.

Stability in electoral competition: A case for multiple votes

It is well known that the Hotelling-Downs model generically fails to admit an equilibrium when voting takes place under the plurality rule (Osborne 1993). This paper studies the Hotelling-Downs model considering that each voter is allowed to vote for up to k candidates and demonstrates that an equilibrium exists for a non-degenerate class of distributions of voters’ ideal policies - which includes all log-concave distributions - if and only if (k=2). That is, the plurality rule (k=1) is shown to be the unique k-vote rule which generically precludes stability in electoral competition. Regarding the features of k-vote rules’ equilibria, first, we show that there is no convergent equilibrium and, then, we fully characterize all divergent equilibria. We study comprehensively the simplest kind of divergent equilibria (two-location ones) and we argue that, apart from existing for quite a general class of distributions when k = 2, they have further attractive properties - among others, they are robust to free-entry and to candidates’ being uncertain about voters’ preferences.

Turnout and Polarization Under Alternative Electoral Systems

This chapter presents a formal model of electoral competition where parties’ platforms are endogenously chosen and depend on the degree of the electoral rule disproportionality. We first show that proportional electoral systems generate centrifugal forces that increase candidate differentiation. This in turn implies that more proportional systems are associated with lower levels of abstention from indifference. This two-step theoretical prediction of the effect of electoral systems on turnout is then empirically validated even when we jointly control for the prevailing pivotality and party-system size hypotheses. Thus, our work highlights an additional link in the proportionality-turnout nexus.

Symmetric zero-sum games with only asymmetric equilibria

We know that a) two-player symmetric zero-sum games with non-empty equilibrium sets always admit symmetric equilibria and that b) two-player and multiplayer symmetric non-zero-sum games might have only asymmetric equilibria (Fey, 2012). But what about multiplayer symmetric zero-sum games? This paper shows that these games might also have only asymmetric equilibria. One of the examples employed to illustrate this point is the three-candidate version of the popular Hotelling–Downs model of electoral competition. This demonstrates that symmetric games with only asymmetric equilibria are not technical paradoxes but are integrated in economics and political science literature for quite a while.

Incomplete information, proportional representation and strategic voting

We introduce incomplete information to a multiparty election under proportional representation: each voter knows her preferences and votes strategically to maximize her payoffs, but is uncertain about the number and the preferences of the other voters. Parties are assumed to be purely office motivated and, hence, the resulting governments are always minimum winning. In this framework, we prove (a) generic existence of equilibria where only two parties receive a positive fraction of the votes and therefore lead to single-party governments and (b) generic inexistence of equilibria that lead to coalition governments. That is, contrary to common wisdom, a proportional rule is found not to promote sincere voting and to be favorable towards single-party governments. The existence of two-party equilibria that lead to single-party governments is robust to parties having ideological concerns.

Hotelling was Right

This paper proves existence of a subgame perfect equilibrium in Hotellings original (unidimensional city, linear transportation costs, uniform distribution of the consumers, two firms with identical and constant marginal cost, perfectly inelastic demand) location–price game such that in the location subgame the location choices of the firms are pure and identical. The result can be extended to variations of the original setup (multidimensional city, nonlinear transportation costs, nonuniform distribution of consumers, many firms with identical and constant marginal costs, two or more firms with nonidentical but constant marginal costs).

Electoral Thresholds as Coordination Devices

In this paper, we study one‐person–one‐vote parliamentary elections where voters care both about the winner of elections and about the composition of the parliament. Parties enter the parliament if and only if their vote share exceeds some predetermined threshold. We show that equilibria generically exist in which all parties obtain a non‐degenerate vote‐share and, perhaps more importantly, we show that the size of the electoral threshold acts as a coordination device, which crucially affects the win prospects of the Condorcet winner party. In particular, we argue that the win prospects of the Condorcet winner party decrease with the size of the entry threshold.

Implementation Via Approval Mechanisms

We focus on the single-peaked domain and study the class of Generalized Approval Mechanisms (GAMs): First, players simultaneously select subsets of the outcome space and scores are assigned to each alternative; and, then, a given quantile of the induced score distribution is implemented. Our main finding is that essentially for every Nash-implementable welfare optimum – including the Condorcet winner alternative – there exists a GAM that Nash-implements it. Importantly, the GAM that Nash-implements the Condorcet winner alternative is the first simple simultaneous game with this feature in the literature.

Simple centrifugal incentives in spatial competition

This paper studies the effects of introducing centrifugal incentives in an otherwise standard Downsian model of electoral competition. First, we demonstrate that a symmetric equilibrium is guaranteed to exist when centrifugal incentives are induced by any kind of partial voter participation (such as abstention due to indifference, abstention due to alienation, etc.) and, then, we argue that: (a) this symmetric equilibrium is in pure strategies, and it is hence convergent, only when centrifugal incentives are sufficiently weak on both sides; (b) when centrifugal incentives are strong on both sides (when, for example, a lot of voters abstain when they are sufficiently indifferent between the two candidates) players use mixed strategies—the stronger the centrifugal incentives, the larger the probability weight that players assign to locations near the extremes; and (c) when centrifugal incentives are strong on one side only—say for example only on the right—the support of players’ mixed strategies contain all policies except from those that are sufficiently close to the left extreme.