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Solving minimum-cost shared arborescence problems
No full textInternational audienceIn this work, we consider the minimum-cost shared Steiner arborescence problem (SStA). In this problem, the goal is to find a minimum-cost subgraph, which is shared among multiple entities and each entity is able to establish a cost-efficient Steiner arborescence. The SStA has been recently used in the literature to establish shared functional modules in protein-protein interaction networks.We propose a cut-based formulation for the problem, and design two exact algorithmic approaches: one based on the separation of connectivity cut inequalities, and the other corresponding to a Benders decomposition of the former model. Both approaches are enhanced by various techniques, including (i) preprocessing, (ii) stabilized cut generation, (iii) primal heuristics, and (iv) cut management. These two algorithmic alternatives are computationally evaluated and compared with a previously proposed flow-based formulation. We illustrate the effectiveness of the algorithms on two types of instances derived from protein-protein interaction networks (available from the previous literature) and from telecommunication access networks
The Effect of Joint Auditor Pair Composition on Audit Quality: Evidence from Impairment Tests
No full textInternational audienceUsing a sample of firms from France, where the law requires the use of two auditors, we study the effect of auditor pair composition on audit quality by examining a specific account, goodwill impairment. We document that firms audited by a Big 4–non‐Big 4 auditor pair (BS) are more likely to book an impairment and book a larger impairment than firms audited by a Big 4–Big 4 auditor pair (BB) when low‐performance indicators suggest a greater likelihood of impairment. Moreover, firms audited by a BB pair reduce impairment disclosures when they book impairments, while firms audited by a BS pair do not, suggesting lower transparency for firms audited by a BB pair. Our results inform investors and firms in mandatory joint audit regimes, as well as regulators who are considering requiring joint audits
Decomposition methods for the two-stage stochastic Steiner tree problem
No full textInternational audienceA new algorithmic approach for solving the stochastic Steiner tree problem based on three procedures for computing lower bounds (dual ascent, Lagrangian relaxation, Benders decomposition) is introduced. Our method is derived from a new integer linear programming formulation, which is shown to be strongest among all known formulations. The resulting method, which relies on an interplay of the dual information retrieved from the respective dual procedures, computes upper and lower bounds and combines them with several rules for fixing variables in order to decrease the size of problem instances. The effectiveness of our method is compared in an extensive computational study with the state-of-the-art exact approach, which employs a Benders decomposition based on two-stage branch-and-cut, and a genetic algorithm introduced during the DIMACS implementation challenge on Steiner trees. Our results indicate that the presented method significantly outperforms existing ones, both on benchmark instances from literature, as well as on large-scale telecommunication networks
Gender Interaction in Teams: Experimental Evidence on Performance and Punishment Behavior
No full textInternational audienc
2ème convention de recherche relative aux déterminants de la formation des niveaux de loyers
No full textLe rapport contient deux études empiriques originales. La première étude exploite pour la première fois les données collectées par 15 observatoires des loyers dans le but de réaliser une typologie des marchés locatifs privés en France en 2015. Cette typologie est basée sur les prix hédoniques estimés en incluant les caractéristiques structurelles et une grande variété de caractéristiques contextuelles des logements (socio-économiques, aménités/désaménités environnementales, accessibilité) et en tenant compte de l’hétéroscédasticité et de l’autocorrélation spatiale des erreurs. Si la variance des montants des loyers au sein d’un même observatoire des loyers s’explique en grande partie par les caractéristiques structurelles des logements, les variables socioéconomiques et les variables d’aménité sont néanmoins des déterminants significatifs. Cinq groupes de communes centres présentant des mécanismes similaires de fixation des montants des loyers résultent de l’analyse, séparant les communes centres des grandes métropoles avec un marché tendu, celles avec un marché moins tendu, les communes littorales touristiques, les villes industrielles en déficit d’attractivité et le cas particulier sétois. La deuxième étude présente les résultats d'une analyse visant à évaluer l’impact de l’économie collaborative sur le marché locatif privé en France, à travers l’exemple de Airbnb. Cette plateforme de location de logements entre particuliers en France connait un fort succès. Selon une étude publiée par Airbnb en collaboration avec le cabinet d'études économiques Astérès, 8 millions de voyageurs ont utilisé Airbnb pour séjourner en France en 2016, ce qui place notre pays en deuxième position dans le classement des pays les plus demandés sur la plateforme, Paris étant la première « ville Airbnb » au monde. Dans cette note, nous présentons d’abord les résultats d’une analyse descriptive de données Airbnb provenant de la société AirDNA (https://www.airdna.co/) et nous construisons un ensemble d’indicateurs permettant de caractériser le phénomène Airbnb. Nous réalisons ensuite une étude économétrique visant à évaluer l’impact de l’activité de Airbnb sur les loyers du parc locatif privé de douze villes françaises. Les résultats sont obtenus via l’estimation d’un modèle hédonique spatio-temporel robuste à l’autocorrélation spatiale et l’hétéroscédasticité de formes inconnues, sur la période 2014-2015. Cette étude pourra ainsi alimenter la réflexion de l'Etat et des collectivités territoriales sur l'encadrement de l'activité des plateformes de location, dans la continuité de la loi du 7 octobre 2016 pour une République numérique
Point de vue : les nouveaux chantiers du management de la diversité
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Evaluating knowledge types in design science research : an integrated framework
No full textInternational audienceAs the design science research (DSR) paradigm has evolved, several frameworks and taxonomies have been proposed to aid researchers in understanding and applying DSR principles and practices to evaluate the knowledge produced. This paper attempts to integrate two such efforts, the evaluation methods taxonomy and the genres of inquiry framework, in an attempt to derive a more complete evaluation standard. The integration is based on various knowledge types, using mapping and merging techniques. Doing so results in three artifacts. The first is the integrated framework which refines the genres of inquiry framework with six recognized knowledge types (definitional, descriptive, prescriptive, explanatory, predictive, and explanatory and predictive). Evaluation criteria for each knowledge type emerge from the integration. The second contribution is a guidance scheme that helps in determining relevant evaluation criteria, based upon the type of DSR contribution and the role of the evaluator (DSR researcher, author, reader, or reviewer). Finally, the approach to the integration, including the integration algorithm, is adaptable to other contexts where criteria to evaluate different knowledge types need to be integrated
An equilibrium search model of the French dual market for medical services
No full textESSEC Working paper. Document de Recherche ESSEC / Centre de recherche de l’ESSEC. ISSN : 1291-9616The French market for specialist physician care has a dual structure, including a sector 1 with regulated fees, and a sector 2 where physicians can freely choose fees. Patients who undergo a sequential search process for the best medical o¤er develop a reservation fee decision rule. We analyzed physicians decisions to work in sector 1 or in sector 2, and their choice of fee in sector 2. The model features several pure strategy equilibria that can be ordered with respect to patient welfare. Policy implications follow