Monitoring optimistic agents

Monitoring is typically included in economic models of crime thanks to a probability of detection, constant across individuals. We build on recent results in psychology to argue that comparative optimism deeply affects this standard relation. To this matter, we introduce an experiment involving proper incentives that allow a measurement of optimism bias. Our experiments support the relevance of so-called comparative optimism in decision under risk. In the context of illegal activities, our results provide a guide into costless devices to undermine fraud, through well-designed information campaigns.Optimism; Risk aversion; Monitoring design; Illegal activity; Experimental economics

Simulation of orthotic treatment in adolescent idiopathic scoliosis using a subject-specific finite element model

Adolescent idiopathic scoliosis (AIS) is a threedimensional deformity of the spine, often progressing rapidly during the growth spurt. Severe scoliosis can lead to significant degradation of quality of life and functional impairment; the aim of early orthotic treatment is to slow down curvature progression until skeletal maturity. Efficacy of bracing has often been questioned (Negrini et al., 2010; Weinstein et al., 2013), and often relies on the orthotist’s experience since objective methods to design and predict brace action are still in development (Cobetto et al., 2014). A clinically-relevant method for the evaluation of brace simulation in AIS was recently presented (Vergari et al., 2015) and applied to preliminarily validate a finite element model (FEM) of the trunk. The aim of this work was to improve the simulation of brace action on scoliotic trunks and to validate the model on a larger cohor

Towards a predictive simulation of brace action in adolescent idiopathic scoliosis

The data collection was approved of by the ethical commit-tee (CPP 6001 Ile de France V), and patients and their parents signed an informed consent.Bracing is the most common treatment to stop the progression of adolescent idiopathic scoliosis. Finite element modeling could help improve brace design, but model validation is still a challenge. In this work, the clinical relevance of a predictive and subject-specific model for bracing was evaluated in forty-six AIS patients. The model reproduces brace action and the patient’s spinopelvic adjustments to keep balance. The model simulated 70% or more patients with geometrical parameters within a preselected tolerance level. Although the model simulation of the sagittal plane could be improved, the approach is promising for a realistic and predictive simulation of brace action.The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling (with the support of ParisTech and Yves Cotrel Foundations, Proteor, Société Génerale and Covea). We are also thankful to David Barrie Colridge for his support

Quasi-automatic early detection of progressive idiopathic scoliosis from biplanar radiography: a preliminary validation

Purpose To validate the predictive power and reliability of a novel quasi-automatic method to calculate the severity index of adolescent idiopathic scoliosis (AIS). Methods Fifty-five AIS patients were prospectively included (Age: 10-15, Cobb: 16° ± 4°). Patients underwent low-dose biplanar x-rays and a novel fast method for 3D reconstruction of the spine was performed. They were followed until skeletal maturity (stable patients) or brace prescription (progressive patients). The severity index was calculated at the first exam, based on 3D parameters of the scoliotic curve, and it was compared with the patient’s final outcome (progressive or stable). Three operators have repeated the 3D reconstruction twice for a subset of 30 patients to assess reproducibility (through Cohen’s kappa and intraclass correlation coefficient). Results 85% of the patients were correctly classified as stable or progressive by the severity index, with a sensitivity of 92% and specificity of 74%. Substantial intra-operator agreement and good inter-operator agreement were observed, with 80% of the progressive patients correctly detected at the first exam. The novel severity index assessment took less than 4 minutes of operator time. Conclusions The fast and semi-automatic method for 3D reconstruction developed in this work allowed for a fast and reliable calculation of the severity index. The method is fast and user friendly. Once extensively validated, this severity index could allow very early initiation of conservative treatment for progressive patients, thus increasing treatment efficacy and therefore reducing the need for corrective surgery.BiomecA

Self-confidence and behavioral labor economics : three experimental essays

Ce manuscrit comporte trois essais qui partagent l’objectif commun d’évaluer l’impact de la confiance en soi sur les décisions des agents économiques à l’aide de la méthode expérimentale. Ce travail se concentre sur trois thèmes relatifs à l’économie comportementale du travail : le travail au noir, la recherche d’emploi et le travail en équipe. Le premier chapitre analyse les biais d’optimisme dans le contexte du travail irrégulier. Ce travail fournit une mesure des biais d’optimisme à travers un processus de décision. Les résultats montrent que les modalités d’annonce du contrôle altèrent la perception du risque : la désignation du nombre d’agents aléatoirement contrôlés tend à encourager l’optimisme des fraudeurs. Le second chapitre étudie comment l’incertitude quant à l’habileté et l’estime que les demandeurs d’emploi ont d’eux-mêmes affectent leurs décisions de recherche. Les résultats montrent qu’en moyenne les agents peu habiles ne modifient pas leur salaire de réserve, alors que les sujets très habiles tendent à diminuer leurs exigences salariales et donc à stopper plus rapidement leur recherche. Cependant, les décisions des agents peu habiles ne sont pas homogènes : les agents peu compétents ont des exigences salariales d’autant plus élevées qu’ils ont une haute estime d’eux-mêmes. Le troisième chapitre vise à évaluer dans quelle mesure l’image que les travailleurs ont d’eux-mêmes conditionne leur choix d’effort lorsqu’ils travaillent en groupe. Les résultats montrent que les agents qui sur évaluent (sous-évaluent) leur habileté exercent plus (moins) d’effort que les sujets qui ont une perception correcte de leurs compétences. Les résultats révèlent également que les individus bénéficient de la sur-confiance de leur partenaire, mais pas de leur propre biais, alors que la sous-confiance détériore le bien-être de tous les membres de l’équipe.This dissertation contains three essays that estimate the effects of self-confidence on economic agents’ decisions. An experimental approach is used for those contributions. This work is interested in three topics concerning behavioral labor economics: moonlighting, job search and teamwork. The first chapter investigates the existence of optimism biases in the context of irregular work. This essay proposes a measure of optimism biases through a decision process. The results show that the way the monitoring policy is announced deeply affects the perception of the risk at stake: the designation of the number of randomly controlled agents tends to foster the cheats’ optimism. The second chapter studies how the uncertainty on ability and self-esteem of job-seekers affect their search behaviors. The results show that on average the low ability agents’ decisions are not affected by the uncertainty about their ability, whereas the high ability agents tend to decrease their reservation wage and thus to stop their search faster. However, the low ability agents’ decisions are not homogeneous: the higher the worker’s self-esteem is, the higher his reservation wage is. The third chapter aims at estimating how workers’ self-image biases affect effort choices and team production. The results show that the workers who overestimate (underestimate) their ability provide higher (lower) effort levels than the unbiased. The results also reveal that the agents benefit from their partner’s confidence, but not from their own bias. Conversely, the presence of underconfident agents in the team damages the welfare of both teammates

Rémunération et effort des travailleurs dans un cadre collectif

National audienc

Marché du travail, évaluation et économie expérimentale

International audienceL'économie comportementale et l'économie expérimentale ont connu un formidable essor au cours des dernières décennies. L'objectif de cet article est de présenter, au travers d'un cadre général d'analyse et d'exemples d'applications, l'intérêt de l'économie expérimentale pour l'évaluation des politiques publiques sur le marché du travail. L'économie expérimentale et les méthodes alternatives existantes apparaissent comme des outils d'analyse complémentaires dans l'étude des politiques publiques. En particulier, les résultats issus de l'économie expérimentale apportent un éclairage critique sur les modèles théoriques sous-jacents à l'étude des politiques du marché du travail