Abstract: We consider collective choice problems where a set of agents have to choose in alternative front a finite set and agents may or may not become users of the chosen alternative. All allocation is a pair given by the chosen alternative and the set Of its users. Agents have gregarious Preferences over allocations: given all allocation, they prefer that the set of users becomes larger. We require that the final allocation be efficient and stable (no agent call be forced to be a User and no agent who wants to be it User call be excluded). We propose a two-stage sequential mechanism whose unique subgame perfect equilibrium Outcome is all efficient and stable allocation which also satisfies a maximal participation property. (C) 2008 Elsevier Inc. All rights reserved.

Abstract: We consider the classic cake-division problem when the cake is a heterogeneous good represented by an interval in the real line. We provide a mechanism to implement, in all anonymous way all envy-free and efficient allocation when agents have private information on their preferences. The mechanism is a multi-step sequential game form in which each agent at each step receives a morsel of the cake that is the intersection of what she asks tor herself and what the other agent concedes to her. (c) 2008 Elsevier Inc. All rights reserved.

Abstract: In this paper we study the optimal design of credit derivative contracts when banks have private information about their ability in the loan market and are subject to capital requirements. First, we prove that when banks are subject to a maximum loss capital requirement the optimal signaling contract is a binary credit default basket. Second, we show that if credit derivative markets are opaque then banks cannot commit to terminal-date risk exposure, and therefore the optimal signaling contract is more costly. The above results allow us to discuss the potential implications of different capital adequacy rules for the credit derivative markets. (c) 2008 Elsevier Inc. All rights reserved.

Abstract: In this paper, we study two-person bargaining problems represented by a space of alternatives, a status quo point, and the agents' preference relations on the alternatives. The notion of a family of increasing sets is introduced, which reflects a particular way of gradually expanding the set of alternatives. For any given family of increasing sets, we present a solution which is Pareto optimal and monotonic with respect to this family, that is, it makes each agent weakly better off if the set of alternatives is expanded within this family. The solution may be viewed as an expression of equal-opportunity equivalence as defined in Thomson [Soc. Choice Welf. 11 (1994) 137-156]. It is shown to be the unique solution that, in addition to Pareto optimality and the monotonicity property mentioned above, satisfies a uniqueness axiom and unchanged contour independence. A noncooperative bargaining procedure is provided for which the unique backward induction outcome coincides with the solution. (c) 2004 Elsevier B.V. All rights reserved.

Abstract: We examine the strategy-proof provision of excludable public goods when agents care about the number of other consumers. We show that strategy-proof and efficient social choice functions satisfying an outsider independence condition must always assign a fixed number of consumers, regardless of individual desires to participate. A hierarchical rule selects participants and a generalized median rule selects the level of the Public good. Under heterogeneity in agents' views oil the optimal number of consumers, strategy-proof, efficient, and outsider independent social choice functions are much more limited and in an important case must be dictatorial. (C) 2003 Elsevier Inc. All rights reserved.