Working papers results

In deciding whether to join a coalition or not, an agent must consider both i) the expected power of the coalition and ii) her position in the vertical structure within the coalition. We establish the existence of a positive relationship between the degree of inequality in remuneration across ranks within coalitions and the number of coalitions to be formed endogenously in stable systems. An inherent feature of such coalitions is that they are mixed and balanced, rather than segregated, in terms of members abilities. When the surplus of a coalition is assumed to be linear in its relative power conditional on its size, we also establish the existence of stable systems and characterise them fully: a system is stable if and only if all coalitions are of an ecient size and every agent is paid her marginal contribution.

We consider a decision maker who ranks actions according to the smooth ambiguity criterion of Klibanoff et al. (2005). An action is justifiable if it is a best reply to some belief over probabilistic models. We show that higher ambiguity aversion expands the set of justifiable actions. In turn, this implies that higher ambiguity aversion expands the set of rationalizable actions of a game. Our results follow from a generalization of the duality lemma of Wald (1949) and Pearce (1984).

We analyze political selection in a closed list proportional system where parties have strong gate-keeping power, which they use as an instrument to pursue votes. Parties face a trade-off between selecting loyal candidates or experts, who are highly valued by the voters and thus increase the probability of winning the election. Voters can be rational or behavioral. The former care about the quality mix of the elected candidates in the winning party, and hence about the ordering on the party list. The latter only concentrate on the quality type of the candidates in the top positions of the party list. Our theoretical model shows that to persuade rational voters parties optimally allocate loyalists to safe seats and experts to uncertain positions. Persuading behavioral voters instead requires to position the experts visibly on top of the electoral list. Our empirical analysis, which uses data from the 2013 National election in Italy-held under closed list proportional representation-and from independent pre-electoral polls, is overall supportive of voters' rational behavior. Loyalists (i.e., party officers or former members of Parliament who mostly voted along party lines) are overrepresented in safe positions, and, within both safe and uncertain positions, they are ranked higher in the list.

Paul Krugman has written a very timely paper. It discusses an old issue, that has become very relevant again. My comments address two questions. First, should inflation targeting be reconsidered? Here my answer is a clear and resounding yes. Inflation targeting performed very well in the fight against inflation and in stabilizing inflation expectations. But now, even leaving issues of financial stability aside, monetary policy is faced with different challenges. Second, which features of the inflation targeting framework should be changed? Here I argue that other aspects of the framework are more important than the numerical value of the target. In addressing these questions, I review Paul Krugman's arguments, agreeing with many but not all of them.

The problemof choosing an optimal toolkit day after day,when there is uncertainty concerning the value of different tools that can only be resolved by carrying the tools, is a multi-armed bandit problem with nonindependent arms. Accordingly, except for very simple specifications, this optimization problem cannot (practically) be solved. Decision takers facing this problem presumably resort to decision heuristics, "sensible" rules fordeciding which tools to carry, based on past experience. In this paper, we examine and compare the performance of a variety of heuristics, some very simple and others inspired by the computer-science literature on these problems. Some asymptotic results are obtained, especially concerning the long-run outcomes of using the heuristics, hence these results indicate which heuristics do well when the discount factor is close to one. But our focus is on the relative performance of these heuristics for discount factors bounded away from one, which we study through simulation of the heur istics on a collection of test problems.

Recent applications to the modeling of emission permit markets by means of stochastic dynamic general equilibrium models look into the relative merits of different policy mechanisms under uncertainty. The approach taken in these studies is to assume the existence of an emission constraints that is always binding (i.e. the emission cap is always smaller than what actual emissions would be in the absence of climate policy). Although this might seem a reasonable assumption in the longer term, as policies will be increasingly stringent, in the short run there might be instances where this assumption is in sharp contrast with reality. A notable example would be the current status of the European Emission Trading Scheme. This paper explores the implications of adopting a technique that allows occasionally, rather than strictly, binding constraints. With this new setup the paper sets out to investigate the relative merits of different climate policy instruments under different macro-economic shocks.

Previous research has documented a behavioral distinction between 'social risk' and financial risk. For example, individuals tend to demand a premium on the objective probability of a favorable outcome when that outcome is determined by a human being instead of a randomizing device (Bohnet, Greig, Herrmann, and Zeckhauser 2008; Bohnet and Zeckhauser 2004). In this paper we ask whether social risk is always aversive, answering in the negative and identifying factors that can eliminate, or even change the sign of, the social risk premium. Motivated by the stereotype content model from the social psychology literature, which we argue has straightforward predictions for situations involving social risk (Fiske, Cuddy, and Glick 2007), we focus on two factors: 'warmth', synonymous with intent, and 'competence.' We investigate these factors using a between-subjects experimental design that implements slight modifications of the binary trust game of Bohnet and Zeckhauser across treatments. Our results indicate that h aving risk generated by another human being does not, on its own, lead to a social risk premium. Instead, we find that a positive risk premium is demanded when a counter-party has interests conflicting with one's own (low warmth) and, additionally, is competent. We find a negative social risk premium -i.e., social risk seeking- when the counter-party has contrary interests but lacks competence.

Reciprocity can be a powerful motivation for human behaviour. Scholars argue that it is relevant in the context of private provision of public goods. We examine whether reciprocity can resolve the associated coordination problem. The interaction of reciprocity with cost-sharing is critical. Neither cost-sharing nor reciprocity in isolation can solve the problem, but together they have that potential. We introduce new network notions of reciprocity relations to better understand this. Our analysis uncovers an intricate web of nuances that demonstrate the attainable yet elusive nature of a unique outcome.

Maccheroni, Marinacci, and Rustichini [17], in an Anscombe-Aumann framework, axiomatically characterize preferences that are represented by the variational utility functional where u is a utility function on outcomes and c is an index of uncertainty aversion. In this paper, for a given variational preference, we study the class of functions c that represent V. Inter alia, we show that this set is fully characterized by a minimal and a maximal element, c* and d*. The function c*, also identified by Maccheroni, Marinacci, and Rustichini [17], fully characterizes the decision maker's attitude toward uncertainty, while the novel function d* characterizes the uncertainty perceived by the decision maker.

Land conflicts in developing countries are costly. An important policy goal is to create respect for borders. This often involves mandatory, expensive interventions. We propose a new policy design, which in theory promotes neighborly relations at low cost. A salient feature is the option to by-pass regulation through consensus. The key idea combines the insight that social preferences transform social dilemmas into coordination problems with the logic of forward induction. As a first, low-cost pass at empirical evaluation, we conduct an experiment among farmers in the Ethiopian highlands, a region exhibiting features typical of countries where borders are often disputed. Our results suggest that a low-cost land delimitation based on neighborly recognition of borders could deliver a desired low-conflict situation if accompanied by an optional higher cost demarcation process.