JOSÉ HELENO FARO
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Artigo Científico Ambiguity aversion in the long run: “To disagree, we must also agree”(2016) Araujo, Aloisio; Silva, Pietro da; JOSÉ HELENO FAROArtigo Científico On the confidence preferences model(2012) Chateauneuf, Alain; JOSÉ HELENO FAROIn this paper we study the model of decision under uncertainty consistent with confidence preferences. In that model, a decision maker held beliefs represented by a fuzzy set of priors and tastes captured by a standard affine utility index on consequences. First, we find some interesting properties concerning the well-known maxmin expected utility model, taking into account the point of view of the confidence preferences model. Further, we provide new examples of preferences that capture ambiguity-averse attitudes weaker than ambiguity attitudes featured by maxmin expected utility theory. Finally, we discuss the axiomatic foundations for the confidence preferences model with optimistic behavior.Artigo Científico Financial market structures revealed by pricing rules: Efficient complete markets are prevalent(2018) Araujo, Aloisio; Chateauneuf, Alain; JOSÉ HELENO FAROTrabalho de Evento Dynamic bbjective and subjective rationality(2014) JOSÉ HELENO FARO; Lefort, Jean PhilippeThe objective and subjective rationality model characterizes decision makers (DMs) by two preference relations over uncertain acts and provides a dual perspective on rationality. The Örst preference reáects choices that are rational in an objective sense and the second one expresses choices labeled as subjectively rational. While an objective ranking means that the DM can convince others of the correctness of making them, in a sub jective choice the DM cannot be convinced of the incorrectness of making them. Objective and subjective preferences are represented, respectively, by Bewleyís unanimity rule and a maxmin expected utility, both repre sentations holding the same set of multiple priors. We propose and axiomatize a dynamic model for the objective and subjective rationality theory. The static model speciÖes some set of prior probabilities, which should be then updated in the light of new and rele vant information. We provide two new axioms on the interplay of uncon ditional objective relations and conditional subjective preferences. Such axioms ensure that a conditional subjective relation is also a maxmin ex pected utility preference and the corresponding set of priors is generated by the full Bayesian updating rule. Our main result thus provides a foun dation for sequentially consistent maxmin subjective preferences, where the prior sets are updated according to the prior-by-prior Bayesí rule. Finally, we study the dynamics of objective preferences and its relations with our main result.Artigo Científico Variational bewley preferences(2015) JOSÉ HELENO FAROArtigo Científico Pricing rules and arrow – debreu ambiguous valuation(2012) Araujo, Aloisio; Chateauneuf, Alain; JOSÉ HELENO FAROThis paper considers pricing rules of single-period securities markets with finitely many states. Our main result characterizes those pricing rules C that are super-replication prices of a frictionless and arbitrage-free incomplete asset structure with a bond. This characterization relies on the equivalence between the sets of frictionless securities and securities priced by C. The former captures securities without bid-ask spreads, while the second captures the class of securities where, if some of its delivers is replaced by a higher payoff, then the resulting security is characterized by a higher value priced by C. We also analyze the special case of pricing rules associated with securities markets admitting a structure of basic assets paying one in some event and nothing otherwise. In this case, we show that the pricing rule can be characterized in terms of capacities. This Arrow–Debreu ambiguous state price can be viewed as a generalization for incomplete markets of Arrow–Debreu state price valuation. Also, some interesting cases are given by pricing rules determined by an integral w.r.t. a risk-neutral capacity. For instance, incomplete markets of Arrow securities and a bond are revealed by a Choquet integral w.r.t. a special risk-neutral capacity.Trabalho de Evento Bewley meet Gilboa and Schmeidler: legitimate preferences under uncertainty(2014) JOSÉ HELENO FARO; Ok, Efe; Riella, GilWe model an organization by a preference relation over uncertain acts satisfying a set of axioms capturing a legitimate decision making process. We show that our set of behavioral conditions is equivalent to a legitimate representation of preferences: there exist two nested sets of priors in which the smaller one represents the set of priors from individuals who occupy higher positions within the organization, while the larger one takes into account also probabilistic beliefs from people of lower positions. A legitimate decision that supports an act f against an act g includes authorization, which occurs when the smaller set of priors unanimously deems the act f better than the act g, a la Bewley (2002), and endorsement, which occurs when the larger set of priors deems the act f better than the act g according to a maxmin rule a la Gilboa and Schmeidler (1989).Artigo Científico Dynamic objective and subjective rationality(2019) JOSÉ HELENO FARO; Lefort, Jean PhilippeWe characterize prior-by-prior Bayesian updating using a model proposed by Gilboa, Maccheroni, Marinacci, and Schmeidler (2010) that jointly considers objective and subjective rationality. These rationality concepts are subject to the Be wley unanimity rule and maxmin expected utility, respectively, with a common set of priors and the same utility over consequences. We use this setup with two preference relations to develop a novel rationale for full Bayesian updating of maxmin expected utility preferences.Artigo Científico Cobb-Douglas preferences under uncertainty(2013) JOSÉ HELENO FAROThis paper axiomatizes Cobb-Douglas preferences under uncertainty. First, we extend the original Trockel (Econ Lett 30:7–10, 1989)’s axiomatic foundation to a general state space framework based on the Strong Homotheticity Axiom, obtaining also the incomplete case a la Bewley (Decis Econ Financ 25:79–110, 2002). We show that this key axiom for the Cobb-Douglas expected utility specification is refuted by Ellsberg’s uncertainty aversion behavioral pattern. Our main result provides a set of meaningful axioms characterizing Cobb-Douglas min-expected utility preferences, an important class of uncertainty averse preferences for studying the consequences of ambiguity in finance and other fields. Finally, we present briefly how to obtain more general representations like the variational case.Artigo Científico Ignorance and competence in choices under uncertainty(2014) Casaca, Paulo; Chateauneuf, Alain; JOSÉ HELENO FAROWe propose a model of decision making that captures reluctance to bet when the decision maker (DM) perceives that she lacks adequate information or expertise about the underlying contingencies. On the other hand, the same DM can prefer to bet in situations where she feels specially knowledgeable or competent even if the underlying contingencies have vague likelihoods. This separation in terms of sources of uncertainty is motivated by the Heath and Tversky’s competence hypothesis as well as by the Fox and Tversky’s comparative ignorance effect. Formally, we characterize preference relations % over Anscombe – Aumann acts represented by J (f) = min p∈C A u(f)dp + max p∈C A c u(f)dp, where u is an affine utility index on consequences, C is a nonempty, convex and (weak∗ ) compact subset of probabilities measures, and A is a referential chance event. In this model there is a clear separation of ambiguity attitudes. The case E ⊂ A captures possible familiar target events while the case E ⊂ A c might refer to the case of relative ignorance concerning related contingencies. This model captures a special case of event dependence of ambiguity attitudes in which the well known maxmin model is a special case. We also characterize the case where we have a Choquet Expected Utility representation. Journal of Economic Literature Classification Number: D81.