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Geometric and computational hardness of bilevel programming
No full textWe first show a simple but striking result in bilevel optimization: unconstrained smooth bilevel programming is as hard as general extended-real-valued lower semicontinuous minimization. We then proceed to a worst-case analysis of box-constrained bilevel polynomial optimization. We show in particular that any extended-real-valued semi-algebraic function, possibly non-continuous, can be expressed as the value function of a polynomial bilevel program. Secondly, from a computational complexity perspective, the decision version of polynomial bilevel programming is one level above NP in the polynomial hierarchy (-hard). Both types of difficulties are uncommon in non-linear programs for which objective functions are typically continuous and belong to the class NP. These results highlight the irremediable hardness attached to general bilevel optimization and the necessity of imposing some form of regularity on the lower level
Avis de salariés en ligne : les commentaires reflètent-t-ils vraiment les notes ? Une réponse par la distance lexicale
No full textDonner son avis sur l’internet est devenu une habitude dans de nombreux domaines : après avoir essayé un nouveau restaurant, suite à une visite de musée, à la réception de son nouveau smartphone, etc. Les employeurs sont aussi concernés par cette tendance à l’évaluation généralisée. Des plateformes se sont spécialisées dans la publication d’avis de salariés anonymes et accompagnés de notes. L’arrivée de Glassdoor sur le territoire français à partir de 2014 a développé les usages de ce type de traces nouvelles pour des employeurs et des candidats à un recrutement jusque-là habitués aux seules communications institutionnelles, souvent orientées par la logique de marque employeur
A model of vertical restraints and labeling: the case of green gases
Full text linkA labeling system for green gases, such as green hydrogen and bio-methane,
could enable retailers to leverage consumers’ willingness to pay for environmental quality while promoting the adoption of these cleaner alternatives. However, the significant cost gap between green and conventional gases raises concerns about the efficacy of such a label, particularly in markets with complex value chains such as road transportation. We develop a stylized model of a gas-based road transport market to evaluate whether the market’s organization could be as efficient
as a labeling policy when consumers lack direct information about production
methods. With the label, producers prefer to exploit the double marginalization to the detriment of social welfare. However, this allows the high-quality producer to cover its fixed costs. Producers can use vertical restraints to convey quality information to consumers without the label. The informational problem creates a trade-off between the intensity of competition (driven by perceived qualities) and cost efficiency. Implementing an optimal label policy depends on the cost gap between qualities and consumers’ expectations about the share of green gas in the market. Under the current cost gap, if consumers were to be informed about the current production landscape, it is possible that their beliefs would lean towards
a relatively pessimistic view. In such a case, the label would be socially optimal
The welfare cost of ignoring the beta.
Full text linkBecause of risk aversion, any sensible investment valuation system should value less projects that contribute more to the aggregate risk. In theory, this is done by adjusting discount rates to consumption betas. But in reality, most public institutions use a dis-count rate that is rather insensitive to the risk profile of their investment projects. The economic consequences of the implied misallocation of capital are severe. I calibrate a Lucas model in which the investment opportunity set contains a constellation of projects with different expected returns and risk profiles. The model matches the traditional finan-cial and macro moments, together with the observed heterogeneity of assets’ risk profiles. The welfare loss of using a single discount rate is equivalent to a permanent reduction in consumption that lies somewhere between 15% and 45% depending upon which single discount rate is used
Droit d'alerte du CSE : précisions de ses conditions d'exercice et recevabilité de l'action syndicale (Cass. soc., 3 déc. 2025, no 24-10326 , FS–B)
No full textPatterns in sustainable food choices and policy support : Novel evidence from nine countries
No full textThis analysis uses OECD survey data from over 8,000 households in nine countries. The paper analyses household profiles via latent class analysis on the basis of both diet composition, as well as purchasing habits for products that are generally perceived to be socially responsible. Results reveal four main household profiles that are distinguished by different broad patterns in these two behaviours. Household profiles are found to differ in terms of their sociodemographic characteristics and attitudes towards the environment, as well as with respect to their level of support for various food policies. Interestingly, results regarding the relationship between environmental attitudes and red meat consumption may suggest the existence of another “meat paradox” in the sense that one group of respondents reports high levels of environmental concern but also a high frequency of meat consumption
An Evaluation of Protected Area Policies in the European Union
No full textThe European Union designates 26% of its landmass as protected areas, limiting economic development for biodiversity. We use the staggered introduction of protected areas between 1985 and 2019 to study the selection of protected land and the causal eect of protection on vegetation cover and nightlights. We nd no meaningful impacts on either outcome across four decades, countries, protection cohorts, or land characteristics. These null eects are consistent with the political economy of EU land protection: weak incentives to internalize biodiversity gains, green-glow motives, and area-based targets shape local siting and stringency choices. In practice, strict protection is applied where development pressure is low{so that protection has little bite|while in high-pressure regions, protection is typically weak, imposing only limited constraints on economic activity
