Working papers results

In real-life elections, vote-counting is often imperfect. We analyze the consequences of such imperfections in plurality and runoff rule voting games. We call a strategy profile a robust equilibrium if it is an equilibrium if the probability of a miscount is positive but small.

All robust equilibria of plurality voting games satisfy Duverger's Law: In any robust equilibrium, exactly two candidates receive a positive number of votes. Moreover, robust- ness (only) rules out a victory of the Condorcet loser.

All robust equilibria under runoff rule satisfy Duverger's Hypothesis: First round votes vare (almost always) dispersed over more than two alternatives. Robustness has strong implications for equilibrium outcomes under runoff rule: For large parts of the parameter space, the robust equilibrium outcome is unique.

This is a survey of some of the recent decision-theoretic literature involving beliefs that cannot be quantified by a Bayesian prior. We discuss historical, philosophical, and axiomatic foundations of the Bayesian model, as well as of several alternative models recently proposed. The definition and comparison of ambiguity aversion and the updating of non-Bayesian beliefs are briefly discussed. Finally, several applications are mentioned to illustrate the way that ambiguity (or "Knightian uncertainty") can change the way we think about economic problems.

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The available empirical evidence suggests that the distribution of income and its composition play an important role in explaining tax noncompliance. We address the issue from a macroeconomic point of view, building a dynamic general equilibrium Bewley- Huggett-Aiyagari model that jointly endogenizes tax evasion and income heterogeneity. Our results showthat the model can successfully replicate the salient qualitative and quantitative features of U.S. data. In particular, the model replicates fairly well the shape of the cross-sectional distribution of misreporting rates over true income levels. Furthermore, we show that a switch from progressive to proportional taxation has important quantitative effects on noncompliance rates and tax revenues.

This article compares the impact of plague across Europe during the seventeenth century. It shows that, contrary to received wisdom, seventeenth century plague cannot be considered a "great equalizer": the disease affected southern Europe much more severely than the north. In particular, Italy was by far the area worst struck. Using both archival sources and previously published data, the article introduces a novel epidemiological variable that has not been considered in the literature: territorial pervasiveness of the contagion. This variable is much more relevant than local mortality rates in accounting for the different regional impact of plague. The article shows that pandemics, and not economic hardship, generated a severe demographic crisis in Italy during the seventeenth century --- at a time when northern European populations were growing quickly. Plague caused a "system shock" to the economy of the Italian peninsula that might be key in understanding the start of its relative decline compared to the emerging northern European countries.

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We analyze forward-induction reasoning in games with asymmetric information assuming some commonly understood restrictions on beliefs. Specifically, we assume that some given restrictions Δ on players' initial or conditional first-order beliefs are transparent, that is, not only the restrictions Δ hold, but there is common belief in Δ at every node. Most applied models of asymmetric information are covered as special cases whereby Δ pins down the probabilities initially assigned to states of nature. But the abstract analysis also allows for transparent restrictions on beliefs about behavior, e.g. independence restrictions or restrictions induced by the context behind the game. Our contribution is twofold. First, we use dynamic interactive epistemology to formalize assumptions that capture foward-induction reasoning given the transparency of Δ, and show that the behavioral implications of these assumptions are characterized by the Δ-rationalizability solution procedure of Battigalli (1999, 2003). Second, we study the differences and similarities between this solution concept and a simpler solution procedure put forward by Battigalli and Siniscalchi (2003). We show that the two procedures are equivalent if Δ is 'closed under compositions', a property that holds in all the applications considered by Battigalli and Siniscalchi (2003). We also show that when Δ is not closed under compositions the simpler solution procedure may fail to characterize the behavioral implications of forward induction reasoning.

Interactive epistemology in dynamic games studies forms of strategic reasoning like backward induction and forward induction by formally representing the players' beliefs about each other, conditional on each history. Work on this topic typically relies on epistemic models where states of the world specify both strategies and beliefs. In this literature, strategies are interpreted as objective descriptions of what the players would choose at each history. But the intuitive interpretation of strategy is that of (subjective) contingent plan of action. As players do not delegate their moves to devices that mechanically execute a strategy, plans cannot be anything but beliefs of players about their own behavior. In this paper we analyze strategic reasoning in dynamic games with perfect information by means of epistemic models where behavior is described only by the play path, and players' beliefs include their contingent plans. We define rational planning, a property of beliefs only, and material consistency, which connects plans with choices on the play path. Material rationality is the conjunction of rational planning and material consistency. In perfect information games of depth two, the simplest dynamic games, correct belief in material rationality only implies a Nash outcome, not the backward-induction one. We have to consider stronger assumptions of persistence of belief in material rationality in order to obtain backward induction and forward induction. We relate our work to the existing literature, and we discuss the extension of our analysis to games with imperfect information.

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