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Approximation complexity of min-max (regret) versions of shortest path, spanning tree, and knapsack
No full textThis paper investigates, for the first time in the literature, the approximation of min-max (regret) versions of classical problems like shortest path, minimum spanning tree, and knapsack. For a bounded number of scenarios, we establish fully polynomial-time approximation schemes for the min-max versions of these problems, using relationships between multi-objective and min-max optimization. Using dynamic programming and classical trimming techniques, we construct a fully polynomial-time approximation scheme for min-max regret shortest path. We also establish a fully polynomial-time approximation scheme for min-max regret spanning tree and prove that min-max regret knapsack is not at all approximable. We also investigate the case of an unbounded number of scenarios, for which min-max and min-max regret versions of polynomial-time solvable problems usually become strongly NP-hard. In this setting, non-approximability results are provided for min-max (regret) versions of shortest path and spanning tree.ouinonouirechercheInternationa
Dependencies between players in Boolean games
No full textBoolean games are a logical setting for representing static games in a succinct way, taking advantage of the expressive power and conciseness of propositional logic. A Boolean game consists of a set of players, each of them controls a set of propositional variables and has a specific goal expressed by a propositional formula. There is a lot of graphical structures hidden in a Boolean game: the satisfaction of each player’s goal depends on players whose actions have an influence on these goals. Even if these dependencies are not specific to Boolean games, in this particular setting they give a way of finding simple characterizations of Nash equilibria and computing them.ouinonouirechercheInternationa
Inputs, Gender Roles or Sharing Norms? Assessing the Gender Performance Gap Among Informal Entrepreneurs in Madagascar
No full textNous utilisons un échantillon représentatif d’entrepreneurs informels à Antananarivo, Madagascar, pour mesurer et expliquer l'existence d'un écart de performance entre les unités de production informelles dirigées par des hommes et celles dirigées par des femmes. Une fois pris en compte les niveaux des facteurs de production, de capital humain, le secteur d'activité, l'année et la sélection endogène dans l'entreprenariat, l'écart de valeur ajoutée entre les entreprises féminines et masculines est d’environ 33%, au détriment des femmes. Nous étudions ensuite l’impact différencié des normesde partages au sein de la communauté et de la répartition des tâches au sein du ménage sur la capacitédes hommes et des femmes entrepreneurs à atteindre leur frontière de production. Notre analyse suggère que seuls les entrepreneurs masculins sont sujets à la pression à la redistribution de la part duréseau distant. Pour les femmes, opérer une activité à domicile n’est pas un handicap en soi, mais celaagit plutôt comme un vecteur de transmission des effets négatifs des normes sociales et de répartition des tâches sur la gestion de l’entreprise. Nos résultats sont compatibles avec des situations dans lesquelles les femmes entrepreneures opérant une activité à domicile ressentiraient davantage le poids de leur propre communauté, sans doute à cause de normes de solidarité contraignantes, mais aussi à cause de leurs responsabilités domestiques.We use a representative sample of informal entrepreneurs in Madagascar to add new evidence on themagnitude of the gender performance gap. After controlling for business and entrepreneur characteristics, female-owned businesses exhibit a value added 28 percent lower than their male counterparts. Correcting for endogenous selection into informal self-employment raises the gap by 5 percentage points. We then investigate the role of sharing norms and gender-differentiated allocationof time within the household in the gender performance gap, by estimating their effect on the technicalinefficiency of female and male entrepreneurs. Only male entrepreneurs seem subject to pressure to redistribute from the distant network. Our findings are consistent with situations where women working at home would essentially feel negatively the burden of their own community due to intensesocial norms and obligations in their workplace but also of domestic chores and responsibilities. Wefind evidence of females self-selecting themselves into industries in which they can combine marketorientedand domestic activities.nonnonouirechercheInternationa
Liquidity risk and contagion for liquid funds
No full textFund managers face liquidity problems but they have to distinguish the market liquidity risk implied by their assets and the funding liquidity risk. This latter is due to both the liquidity mismatch between assets and liabilities and the redemption risk due to the possible outflows from clients. The main contribution of this paper is the analysis of contagion looking at common market liquidity problems to detect funding liquidity problems. Using the CDS Bond Spread basis as a liquidity indicator and a state space model with time-varying volatility specification, we show that during the 2007-2008 financial crisis, there exist pure contagion effects both in terms of price and liquidity on the emerging sovereign debt market. This result has strong implication since the main risk for an asset manager is to get stuck with an unwanted position due to a dry-up of market liquidity.nonouirechercheInternationa
France's new economic regulations: insights from institutional legitimacy theory
No full textPurpose – The paper seeks to adopt an institutional view of legitimacy to examine how a sample of French companies reacted to the introduction of the “New Economic Regulations” in French law in 2001 requiring that publicly listed companies disclose environmental information.Design/methodology/approach – The approach used in the paper is both quantitative and qualitative. A content analysis of environmental disclosure provided in annual reports, environmental reports and web sites by 26 French companies listed in the CAC 40 is performed throughout the period 2001-2011.Findings – The findings of this study show a significant and enduring improvement in the quality and quantity of environmental disclosure from 2001 to 2011. Even in the absence of penalties for non-compliance, the NRE law stimulated a stark and positive lasting change in the way that French companies account for their environmental information. These findings are consistent with the institutional view of legitimacy theory whereby legislation provides corporate managers with a representation of relevant audiences' perceptions about social and environmental reporting, prompting them to comply with the law to ensure organizational legitimacy.Originality/value – Social and environmental reporting studies generally adopt a strategic view of legitimacy to examine how organizations use social and environmental reporting to respond strategically to legitimacy threats. This study provides early empirical evidence about the relevance of institutional legitimacy theory in explaining environmental reporting.nonouirechercheInternationa
Trade Agreements and Core Labour Standards
No full textOver the last two decades, a growing number of free trade agreements have included social and labour provisions. This Policy Brief investigates the repercussions of such clauses on the ratification of what are seen as fundamental ILO conventions and on workers‟ rights practices. An empirical estimation indicates that labour provisions have not played a significant role in improving labour practices, and that their effect has been limited to the ratification of ILO conventions. This gap highlights the importance included in trade agreements.nonouinon-rechercheInternationalTravaux universitaire
Covers and approximations in multiobjective optimization
No full textDue to the growing interest in approximation for multiobjective optimization problems (MOPs), a theoretical framework for defining and classifying sets representing or approximating solution sets for MOPs is developed. The concept of tolerance function is proposed as a tool for modeling representation quality. This notion leads to the extension of the traditional dominance relation to t-t- dominance. Two types of sets representing the solution sets are defined: covers and approximations. Their properties are examined in a broader context of multiple solution sets, multiple cones, and multiple quality measures. Applications to complex MOPs are included.nonouirechercheInternationa
Dynamic recovery decision during composite web services execution
No full textDuring the execution of a Composite Web Service (CWS), different faults may occur and cause a Web Service (WS) to fail. To repair failures some strategies can be applied, such as WS retry or substitution, compensation of the performed execution, roll-back, replication, or take checkpoints to later restart the execution. Each strategy has advantages and disadvantages on different execution scenarios and can produce different impact on the CWS QoS, depending on the execution environment and execution state at the moment of the failure. In this paper we propose a model and show experimental results to dynamically decide which recovery strategy is the best choice in terms of the impact on the CWS QoS.nonouirechercheInternationa
Data Reductions and Combinatorial Bounds for Improved Approximation Algorithms
No full textKernelization algorithms in the context of Parameterized Complexity are often based on a combination of data reduction rules and combinatorial insights. We will expose in this paper a similar strategy for obtaining polynomial-time approximation algorithms. Our method features the use of approximation-preserving reductions, akin to the notion of parameterized reductions. We exemplify this method to obtain the currently best approximation algorithms for Harmless Set, Differential and Multiple Nonblocker, all of them can be considered in the context of securing networks or information propagation.nonouirechercheInternationa
