Missing Contracts: On the Rationality of not Signing a Prenuptial Agreement

Many couples do not sign prenuptial agreements, even though this often leads to costly and inefficient litigation in case of divorce. In this paper we show that strategic reasons may prevent agents from signing a prenuptial agreement. Partners which have high productivity in marital activities wish to signal their type by running the risk of a costly divorce. Hence this contract incompleteness arises as a screening device. Moreover, the threat of costly divorce is credible since the lack of an ex-ante agreement leads to a moral hazard problem within the couple, which induces partners to reject any ex-post amicable agreement, under specific circumstances. We also investigate conditions that make this contract incompleteness an optimal form of contracting and we briefly discuss the effects of enforceable and/or mandatory premarital agreements on the rate of divorce and on the social welfare. Finally, our model suggests that there is no major objection in making prenuptial agreements enforceable, but also that there are not good reasons to make them mandatory.asymmetric information, incomplete contracts, prenuptial agreement.

Age-Based Preferences in Paired Kidney Exchange

We consider a model of Paired Kidney Exchange (PKE) with feasibility constraints on the number of patient-donor pairs involved in exchanges. Patients' preferences are restricted so that patients prefer kidneys from compatible younger donors to kidneys from older donors. In this framework, patients with compatible donors may enroll on PKE programs to receive an organ with higher expected graft survival than that of their intended donor. PKE rules that satisfy individual rationality, eciency, and strategy-proofness necessarily select pairwise exchanges. Such rules maximize the number of transplantations among pairs with the youngest donors, and sequentially among pairs with donors of dierent age group

The Strategy-Proof Provision of Public Goods under Congestion and Crowding Preferences

We examine the strategy-proof provision of excludable public goods when agents care not only about the level of provision of a public good, but also the number of consumers. We show that on such domains strategy- proof and efficient social choice functions satisfying an outsider independence condition must be rigid in that they must always assign a fixed number of consumers, regardless of individual desires to participate. The fixed number depends on the attitudes of agents regarding group size - being small when congestion effects dominate (individuals prefer to have fewer other consumers) and large when cost sharing effects dominate (agents prefer to have more consumers). A hierarchical rule selects which consumers participate and a variation of a generalized median rule to selects the level of the public good. Under heterogeneity in agents' views on 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.Public Goods, Congestion, Club Goods, Strategy-Proof

Recursive no-envy

In economics the main efficiency criterion is that of Pareto-optimality. For problems of distributing a social endowment a central notion of fairness is no-envy (each agent should receive a bundle at least as good, according to her own preferences, as any of the other agent's bundle). For most economies there are multiple allocations satisfying these two properties. We provide a procedure, based on distributional implications of these two properties, which selects a single allocation which is Pareto-optimal and satisfies no-envy in two-agent exchange economies. There is no straightforward generalization of our procedure to more than two-agents.no-envy, fair allocation, recursive methods, exchange economies

Equilibrium Selection in Sequential Games with Imperfect Information

Games with imperfect information often feature multiple equilibria, which depend on beliefs off the equilibrium path. Standard selection criteria such as passive, symmetric or wary beliefs rest on ad hoc restrictions on beliefs. We propose a new selection criterion that imposes no restrictions on beliefs: we select the action pro\u85le that is supported in equilibrium by the largest set of beliefs. We conduct an experiment to compare the predictive power of the existing and our novel selection criteria in an application on vertical multi- lateral contracting. We find that our criterion outperforms the other selection criteria

UN ALGORITMO DI CONTATTO RUOTA-ROTAIA PER L'IMPIEGO IN SISTEMI DI CALCOLO IN TEMPO REALE

Nello studio del comportamento dinamico dei veicoli ferroviari uno degli aspetti di maggiore rilevanza è il problema della determinazione delle forze scambiate al contatto ruota-rotaia. Questo problema è tuttora oggetto di studi che da un lato cercano di ottenere risultati di maggiore accuratezza e dall'altro cercano di ridurre i tempi di calcolo. Il lavoro illustra i risultati ottenuti con l'algoritmo di contatto sviluppato presso il Politecnico di Torino, denominato RTCONTACT; questo codice, che è un'evoluzione dell'algoritmo CONPOL, è il risultato di lunghe attività di ricerca, le versioni precedenti sono state utilizzate in cosimulazione con codici MBS e in ambiente Matlab® per simulare il comportamento di veicoli ferroviari. Il codice è stato sviluppato anche basandosi su risultati sperimentali ottenuti da banco prova "Roller-Rig". In questo lavoro si illustrano le principali caratteristiche del codice e si presentano confronti con altri codici numerici, pubblicazioni e normative per i risultati di maggiore interesse per il contatto ruota-rotai

Matching with Partners and Projects

We study a model that is a hybrid of the classical roommate matching model object allocation model. We propose a model where agents are matched in pairs in order to undertake a project. Agents have preferences over both the partner and the project they are assigned to. These preferences over partners and projects are separable and dichotomous. Each agent partitions the set of partners into friends and outsiders, and the set of projects into good and bad ones. Friendship is mutual and transitive. In addition, preferences over projects among friends are correlated (homophily). We define a suitable notion of the weak core and propose an algorithm, the minimum demand priority algorithm (MDPA) that generates an assignment in the weak core. In general, the strong core does not exist but the MDPA assignment satisfies a limited version of the strong core property when only friends can be members of the blocking coalition. The MDPA is also strategy-proof. Finally we show that our assumptions on preferences are indispensable. We show that the weak core may fail to exist if any of the assumptions of homophily, separability anddichotomous preferences are relaxed

Long-term radiographic and clinical-functional outcomes of isolated, displaced, closed talar neck and body fractures treated by ORIF: the timing of surgical management

Background: The main purpose of this retrospective case series study was to evaluate long-term radiographic and clinical outcomes of a consecutive series of patients diagnosed with isolated, displaced, closed talar neck or body fractures treated by open reduction and internal fixation (ORIF). Secondly, the aim was to verify the influence of the location of talar fractures on the outcomes, the prognostic value of the Hawkins sign, whether operative delays promote avascular necrosis (AVN) and if the fractures require emergent surgical management. Methods: From January 2007 to December 2012, at our institution, 31 patients underwent ORIF through the use of screws. On the basis of Inokuchi criteria, the injuries were divided between neck and body fractures, which were classified according to Hawkins and Sneppen, respectively. The patients included were divided into two groups in relation to fracture location and complexity. Radiographic assessment focused on reduction quality, bone healing, the Hawkins sign and post-traumatic arthritis (PTA) development. For the clinical evaluation, clinical-functional scores (AOFAS Ankle-Hindfoot Score; MFS; FFI-17; SF-36) and VAS were determined, and statistical analysis was performed. Results: 27 patients, 19 males and 8 females, mean age 38.3 years, were included with an average follow-up period of 83.2 months (range 49\u2013119). There were 9 neck and 19 body fractures; their reduction was anatomical or nearly anatomical in 22 cases, and all reached radiographic consolidation after a mean period of 3.4 months (range 1.7\u20137). The Hawkins sign was observed in 9 cases, in which necrosis did not develop. With a 0\u201311 day surgical timing interval, more than 60% of the patients obtained good or fair results with different scores, while 18 (66.7%) were completely satisfied (VAS: 9\u201310). The early complications included malunions (21.4%) and wound problems (25%); the late complications involved AVN (25%) and PTA (78.6%). Conclusions: Despite a high rate of long-term complications, satisfactory clinical results were achieved. Talar fracture location did not influence the outcomes, the Hawkins sign was confirmed as a positive prognostic factor, and operation timing did not influence AVN development. Hence, these injuries do not require emergent surgical management by ORIF

Using deceased-donor kidneys to initiate chains of living donor kidney paired donations: algorithms and experimentation

We design a flexible algorithm that exploits deceased donor kidneys to initiate chains of living donor kidney paired donations, combining deceased and living donor allocation mechanisms to improve the quantity and quality of kidney transplants. The advantages of this approach have been measured using retrospective data on the pool of donor/recipient incompatible and desensitized pairs at the Padua University Hospital, the largest center for living donor kidney transplants in Italy. The experiments show a remarkable improvement on the number of patients with incompatible donor who could be transplanted, a decrease in the number of desensitization procedures, and an increase in the number of UT patients (that is, patients unlikely to be transplanted for immunological reasons) in the waiting list who could receive an organ.Comment: To be published in AIES 201

Stable Sharing

We propose a simple model in which agents are matched in pairs in order to complete a task of unit size. The preferences of agents are single-peaked and continuous on the amount of time they devote to it. Our model combines features of two models: assignment games (Shapley and Shubik (1971)) and the division problem (Sprumont (1991)). We provide an algorithm (Select-Allocate-Match) that generates a stable and Pareto efficient allocation. We show that stable allocations may fail to exist if either the single-peakedness or the continuity assumption fail