Giovanna Iannantuoni

Extreme voting under proportional representation: the multidimensional case

We study the strategic behavior of voters in a spatial model of proportional representation, in which the policy space is multidimensional. Our main finding is that in large electorate, under some assumptions on voters’ preferences, voters essentially vote, in any equilibrium, only for the extreme parties.

The effect of ideology on policy outcomes in proportional representation systems

In this paper we propose a model in which there are ideological and strategic voters who vote under proportional rule. We prove that the behavior of ideological voters matters for the determination of the outcome. We show that a subset of strategic voters partially counteracts the votes of the ideological voters.

On stable outcomes of approval, plurality, and negative plurality games

We prove two results on the generic determinacy of Nash equilibrium in voting games. The first one is for negative plurality games. The second one is for approval games under the condition that the number of candidates is equal to three. These results are combined with the analogous one obtained in De Sinopoli (Games Econ Behav 34:270–286, 2001) for plurality rule to show that, for generic utilities, three of the most well-known scoring rules, plurality, negative plurality and approval, induce finite sets of equilibrium outcomes in their corresponding derived games—at least when the number of candidates is equal to three. This is a necessary requirement for the development of a systematic comparison amongst these three voting rules and a useful aid to compute the stable sets of equilibria Mertens (Math Oper Res 14:575–625, 1989) of the induced voting games. To conclude, we provide some examples of voting environments with three candidates where we carry out this comparison.

Divided government and dominance solvability

Using the spatial theory of voting, this paper describes an institutional structure where there are two branches of the government: the executive, elected by plurality rule, and the legislative elected by proportional rule. The resulting policy outcome is described through a compromise between these two branches. The parties announce their position on a policy issue and then voters vote. We prove the uniqueness of Nash equilibrium in the subgame, where the election of the president is known. Moreover, this equilibrium can be obtained by the process of iterated elimination of dominated strategies. We then solve the whole game by backward induction. Furthermore, the policy outcome at equilibrium of the two-stage game is the same of the simultaneous game, where voters simultaneously choose the two branches. The results suggest a moderate behavior of the voters, basically due to the will to balance the policy outcome.

Electing a parliament

We present a model where a society elects candidates belonging to two parties to a national parliament. The electoral rule determines the seats distribution between the two parties. The policy outcome is a function of the number of seats the two parties win in the election. We analyze two electoral rules, multidistrict majority and single district proportional. We prove that under both systems there is a unique pure strategy perfect equilibrium outcome. We compare the outcomes under the two systems.

A purely non-cooperative model of divided government

In this paper I describe an institutional structure in which there are two branches of the government: the executive one, elected by plurality rule, and the legislative one elected by proportional rule. The resulting policy outcome is described through a compromise between these two branches. Given the presidential result, legislative elections are characterized by essentially an unique Nash equilibrium such that any voter on the left of the corresponding policy outcome votes for the leftist party and any voter on the right votes for the rightist party. Moreover, this equilibrium can be obtained by a process of iterated elimination of dominated strategies. The whole game is then solved by backward induction and dominance arguments.

It's a Matter of Confidence: Institutions, Government Stability and Economic Outcomes

The effect of constitutional structures (such as the effect of a presidential vs. a parliamentary system) over policy outcomes has been widely studied in the economic literature. In this paper, we investigate whether stable parliamentary systems and unstable parliamentary systems behave differently in terms of the policy outcomes they implement. We show that accounting for the stability of parliamentary systems generates results that are more robust compared to the previous literature. More precisely, we find that stable parliamentary systems are significantly different both from presidential and from unstable parliamentary ones. Moreover, we show that this result is robust to changes in the set of countries, and to changes in the definition of stability. Finally, we discuss how these results are consistent with the presence of a selection effect in parliamentary systems.

Proportional Representation with Uncertainty

We introduce a model with strategic voting in a parliamentary election with proportional representation and uncertainty about voters’ preferences. In any equilibrium of the model, most voters only vote for those parties whose positions are extreme. In the resulting parliament, a consensus government forms and the policy maximizing the sum of utilities of the members of the government is implemented.

Constitutional Rules and Efficient Policies

This paper compares the ability to select the efficient policy of a parliamentary and a presidential constitutional setup. In order to do it we build a dynamic theoretical model with asymmetric information that succeeds in addressing both the politicians accountability and the competence dimensions. The main difference between the two institutional frameworks is the presence of the confidence vote in the parliamentary system that may cause elections before the natural end of the legislature. The equilibrium predictions suggest that, exactly because of the different incentives created by the confidence vote, the parliamentary system has a higher probability of selecting the efficient policy the higher is the quality of politicians that are member of the legislative body.

Voting for Legislators

In this paper we propose a model with uncertainty in which strategic voters vote, under poportional rule, for a Parliament and parties bargain to form a government. We prove that only consensus government form and only extreme parties take votes.