Working papers results

We investigate the role of 'noise' shocks as a source of business cycle fluctuations. To do so we set up a simple model of imperfect information and derive restrictions for identifying the noise shock in a VAR model. The novelty of our approach is that identification is reached by means of dynamic rotations of the reduced form residuals. We find that noise shocks generate hump-shaped responses of GDP, consumption and investment and account for quite a sizable fraction of their prediction error variance at business cycle horizons.

We build a model of a limit order book and examine the consequences of adding a dark pool. Starting with an illiquid book, we show that book and consolidated fill rates and volume increase, but the spread widens, depth declines and welfare deteriorates. When book liquidity increases, more orders migrate to the dark pool and large traders'welfare improves; but while the spread-increase is dampened, the depth-reduction is amplified and small traders are still worse off. All effects are stronger for a continuous than for a periodic dark pool and when the tick size is large.

IIf citizens of different countries belonging to an economic union adhere to different and deeply rooted cultural norms, when these countries interact their leaders may find it impossible to agree on efficient policies, especially in hard times. Political leaders' actions are bound to express policies that do not violate these norms. This paper provides a simple positive theory and a compelling case study of the importance of cultural clashes when economies integrate, as well as a normative argument about the desirability of institutional integration. Namely, we argue that a political union, with a common institutions and enforcement of rules, is a solution which is most beneficial the greater is cultural diversity in an economic union.

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.