About partial probabilistic information

Suppose a decision maker (DM) has partial information about certain events of a σ-algebra A belonging to set ε and assesses their likelihood through a capacity v. When is this information probabilistic, i.e. compatible with a probability ? We consider three notions of compatibility with a probability in increasing degree of preciseness. The weakest requires the existence of a probability P on A such that P(E) ≥ v(E) for all E ∈ ε, we then say that v is a probability minorant. A stronger one is to ask that v be a lower probability, that is the infimum of a family of probabilities on A. The strongest notion of compatibility is for v to be an extendable probability, i.e. there exists a probability P on A which coincides with v on A. We give necessary and sufficient conditions on v in each case and, when ε is finite, we provide effective algorithms that check them in a finite number of steps.Partial probabilistic information, exact capacity, core, extensions of set functions.

Measuring Inequality Without the Pigou-Dalton Condition

income differentials, deprivation, satifaction, Lorenz dominance, progressive transfers, expected utility, generalized Gini social

From sure to strong diversification

This paper presents a characterization of weak risk aversion in terms of preference for sure diversification. Similarly, we show that strong risk aversion can be characterized by weakening preference for diversification, as introduced by Dekel [11], in what we name preference for strong diversification.Weak risk aversion, strong risk aversion, diversification.

G-continuity, impatience and G-cores of exact games

This paper is concerned with real valued set functions defined on the set of Borel sets of a locally compact σ-compact topological space Ω. The first part characterizes the strong and weak impatience in the context of discrete and continuous time flows of income (consumption) valued through a Choquet integral with respect to an (exact) capacity. We show that the impatience of the decision maker translates into continuity properties of the capacity. In the second part, we recall the generalization given by Rébillé [8] of the Yosida-Hewitt decomposition of an additive set function into a continuous part and a pathological part and use it to give a characterization of those convex capacities whose core contains at least one G-continuous measure. We then proceed to characterize the exact capacities whose core contains only G-continuous measures. As a dividend, a simple characterization of countably additive Borel probabilities on locally compact σ-compact metric spaces is obtained.Impatience, exact and convex capacities, G-cores, σcores, Yosida-Hewitt decomposition.

Increases in risk and demand for risky asset

n this paper, we examine the effect of a decrease in risk on the demand for risky asset in the standard portfolio problem. We introduce a new class of dominance, that we name relative order and we prove that this class of dominance is consistent both with central dominance introduced by Gollier [5] and with mean preserving increase in risk. Finally, we show that some known classes of dominance are particular cases of our new class of dominance.EU model, portfolio choice, mean preserving increase in risk, central dominance, relative simple dominance, relative dominance.

Diversification, Convex Preferences and Non-Empty Core

We show, in the Choquet expected utility model, that preference for diversification, that is, convex preferences, is equivalent to a concave utility index and a convex capacity. We then introduce a weaker notion of diversification, namely ``sure diversification.'' We show that this implies that the core of the capacity is non-empty. The converse holds under concavity of the utility index. This property is shown to be equivalent to the notion of comonotone diversification\,; notion that we introduce in the paper. Finally, in the expected utility model, all these notions of diversification are equivalent and are represented by the concavity of the utility index.

Some Fubini theorems on product sigma-algebras for non-additive measures

We give some Fubini's theorems (interversion of the order of integration and product capacities) in the framework of the Choquet integral for product sigma-algebras. Following Ghirardato this is performed by considering slice-comonotonic functions. Our results can be easily interpreted for belief functions, in the Dempster and Shafer setting.Choquet integral, product capacity.

Ambiguity Aversion and Absence of Trade

What is the effect of ambiguity aversion on trade? Although in a Bewley's model ambiguity aversion always lead to less trade, in other models this is not always true. However, we show that if the endowments are unambiguous then more ambiguity aversion implies less trade, for a very general class of preferences. The reduction in trade caused by ambiguity aversion can be as severe as to lead to no-trade. In an economy with MEU decision makers, we show that if the aggregate endowment is unanimously unambiguous then every Pareto optima allocation is also unambiguous. We also characterize the situation in which every unanimously unambiguous allocation is Pareto optimal. Finally, we show how our results can be used to explain the home-bias effect. As a useful result for our methods, we also obtain an additivity theorem for CEU and MEU decision makers that does not require comonotonicity JEL Code: D51, D6, D8no-trade results, ambiguity aversion, Pareto optimality.

Choice under Uncertainty with the Best and Worst in Mind: Neo-additive Capacities

The concept of a non-extreme-outcome-additive capacity (neo-additive capacity ) is introduced. Neo-additive capacities model optimistic and pessimistic attitudes towards uncertainty as observed in many experimental studies. Moreover, neo-additive capacities can be applied easily in economic problems, as we demonstrate by examples. This paper provides an axiomatisation of Choquet expected utility with neo-capacities in a framework of purely subjective uncertainty.

Modeling attitudes toward uncertainty through the use of the Sugeno integral

The aim of the paper is to present under uncertainty, and in an ordinal framework, an axiomatic treatment of the Sugeno integral in terms of preferences which parallels some earlier derivations devoted to the Choquet integral. Some emphasis is given to the characterization of uncertainty aversion.Sugeno integral; uncertainty aversion; preference relations; ordinal information