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La régénération des infrastructures ferroviaires : Une transition sans fin ?
No full textInternational audienceQuelques recherches sur les moteurs internet qui mesurent le degré d’utilisation d’un terme le confirment, l’usage du terme « régénération » a fait un véritable bond à partir du tournant desannées 2000. Si sa diffusion se tasse puis s’affaiblit doucement dans le monde anglophone, son utilisation poursuit une pente croissante dans le monde francophone. Le terme émane dessciences de la nature et il possède une définition précise en médecine. La médecine régénérative (ou régénératrice) vise la réparation ou le remplacement de cellules, tissus ouorganes pour restaurer une fonction altérée du corps humain. Sorti de ce domaine disciplinaire, le terme est certes moins ubiquiste que celui, encore plus invasif, de résilience.Cependant, il a néanmoins envahi tous les champs de l’action sur la ville et ses équipements.Les architectes, urbanistes, gestionnaires d’infrastructures et de réseaux l’emploient couramment, et de proche en proche la société et le monde politique le reprennent, au pointque sa signification précise semble de plus en plus floue, comme le dénonce dans une tribune récente du journal Le Monde une association spécialisée dans la production agricole biologique 1 . Quelles pratiques et quelles significations sont donc associées à la notion de régénération lorsque celle-ci concerne des infrastructures, c’est-à-dire des quantitésd’artefacts physiques hautement complexes enchevêtrées avec des structures de savoir et de pouvoir qui soutiennent, notamment dans nos sociétés avancées, toutes les superstructureséconomiques, environnementales et sociales qui font notre quotidien ? Le besoin d’utiliser ce terme spécifique plutôt que ceux de réparation, restauration ou modernisation nous dit-ilquelque chose de la manière dont les parties prenantes, des chercheurs les plus avancés aux techniciens de maintenance les plus humbles, se représentent les capacités d’évolution denotre environnement physique
Bernoulli variables, classical exclusion processes and free probability
No full text40 pages, submitted to the special issue of the Annales H. Poincare in memory of Krzysztof GawedzkiInternational audienceWe present a new description of the known large deviation function of the classical symmetric simple exclusion process by exploiting its connection with the quantum symmetric simple exclusion processes and using tools from free probability. This may seem paradoxal as free probability usually deals with non commutative probability while the simple exclusion process belongs to the realm of classical probability. On the way, we give a new formula for the free energy -- alias the logarithm of the Laplace transform of the probability distribution -- of correlated Bernoulli variables in terms of the set of their cumulants with non-coinciding indices. This latter result is obtained either by developing a combinatorial approach for cumulants of products of random variables or by borrowing techniques from Feynman graphs
The unusual French policy mix towards labour market inequalities
No full textInternational audienceThis short paper presents an overview of the French policy mix towards labour market inequalities, consisting of a high minimum wage together with targeted payroll tax cuts around the minimum wage. It reviews the recent literature documenting the impact of that policy mix on employment and wage inequality. The main takeaways are that pre‐tax wage inequality has been increasing in France rather like it has in the UK and the US, while net wage inequality has decreased and then remained stable. The employment experience for the middle age group is also very close in France to the one in the UK and the US, while it differs markedly at young and older ages. The paper offers two more general thoughts on how to make progress in comparing policy options. First, most studies tend to give too much weight to tax and benefit reforms in being able to reduce inequality as they disregard incidence mechanisms, and fail to incorporate properly longer‐term effects of other policies on pre‐tax inequality. Second, the design of effective policy should always incorporate simplicity and salience. Failure to do so is likely to lead to little expected impact of such policies
The Economics of the Informal Sector: New Estimates, New Implications for OECD countries
No full textThis paper explores the dynamics and implications of the informal sector within OECD countries, employing a novel estimation approach based on an endogenous growth model. The model integrates both formal and informal sectors, incorporating public services and key determinants of informality. By calibrating this model with OECD data from 1996 to 2016, we derive significant insights into the size and impact of the informal sector. Our findings reveal that, on average, the informal sector constitutes 19.98% of the economy. Policy adjustments influencing the informal sector exhibit a nonlinear effect on economic growth. Specifically, increased formal sector taxation, reduced penalties on informal activities, enhanced access to public goods, and improved quality of government institutions all dynamically interact to shape the informal sector's size and its economic consequences. This study underscores the necessity of a nuanced policy approach, considering the structural characteristics of the economy to optimize growth while managing informality effectively.Ce papier explore les dynamiques et les implications du secteur informel dans les pays de l'OCDE, en utilisant une nouvelle approche d'estimation basée sur un modèle de croissance endogène. Le modèle intègre à la fois les secteurs formel et informel, en tenant compte des services publics et des principaux déterminants de l'informalité. En calibrant ce modèle avec des données de l'OCDE de 1996 à 2016, nous tirons des enseignements significatifs sur la taille et l'impact du secteur informel. Nos résultats révèlent qu'en moyenne, le secteur informel représente 19,98 % de l'économie. Les ajustements politiques influençant le secteur informel montrent un effet non linéaire sur la croissance économique. Plus précisément, l'augmentation de la fiscalité du secteur formel, la réduction des pénalités sur les activités informelles, l'amélioration de l'accès aux biens publics et l'amélioration de la qualité des institutions gouvernementales interagissent de manière dynamique pour façonner la taille du secteur informel et ses conséquences économiques. Cette étude souligne la nécessité d'une approche politique nuancée, tenant compte des caractéristiques structurelles de l'économie pour optimiser la croissance tout en gérant efficacement l'informalité
Targeting Disaster Aid: A Structural Evaluation of Large Earthquake Reconstruction Program
No full textThis paper studies the question of how to target aid after a natural disaster.Disaster aid programs often use property damage as a criterion for eligibility. A household's ability to insure against shocks may be harder to observe but more important in determining how the disaster affects welfare. We develop a model of household demand for reconstruction aid and estimate the model parameters using a household survey following the 2015 Nepal earthquake. Key model predictions are validated using a spatial regression discontinuity design. We use the model to estimate welfare from counterfactual targeting strategies. Conditioning aid on property damages does not significantly improve welfare relative to allocating aid randomly. An untargeted approach that divides the aid budget equally among all households in the affected areas yields larger welfare gains. Using resources to assess property damages for targeting purposes may not be cost effective
Epidémies dues à un arbovirus transmis par le moustique Aedes albopictus en France hexagonale: probabilité d'apparition, ampleur de la transmission et impacts sanitaires, économiques et sociaux
No full textCitation suggérée : Anses. (2024). Epidémies dues à un arbovirus transmis par le moustique Aedes albopictus enFrance hexagonale : probabilité d'apparition, ampleur de la transmission et impacts sanitaires,économiques et sociaux (saisine 2022-SA-0146). Maisons-Alfort : Anses, 247 p
Monitoring macroplastics in aquatic and terrestrial ecosystems: Expert survey reveals visual and drone-based census as most effective techniques
No full textInternational audienceAnthropogenic litter, such as plastic, is investigated by the global scientific community from various fields employing diverse techniques. The goal is to assess and finally mitigate the pollutants' impacts on the natural environment. Plastic litter can accumulate in different matrices of aquatic and terrestrial ecosystems, impacting both biota and ecosystem functioning. Detection and quantification of macroplastics, and other litter, can be realized by jointly using visual census and remote sensing techniques. The primary objective of this research was to identify the most effective approach for monitoring macroplastic litter in riverine and marine environments through a comprehensive survey based on the experiences of the scientific community. Researchers involved in plastic pollution evaluated four litter occurrence and flux investigation methods (visual census, drone-based surveys, satellite imagery, and GPS/GNSS trackers) through a questionnaire. Traditional visual census and drone deployment were deemed as the most popular approaches among the 46 surveyed researchers, while satellite imagery and GPS/GNSS trackers received lower scores due to limited field validation and short performance ranges, respectively. On a scale from 0 to 5, visual census and drone-based surveys obtained 3.5 and 2.0, respectively, whereas satellite imagery and alternative solutions received scores lower than 1.2. Visual and drone censuses were used in high, medium and low-income countries, while satellite census and GPS/GNSS trackers were mostly used in high-income countries. This work provides an overview of the advantages and drawbacks of litter investigation techniques, contributing i) to the global harmonization of macroplastic litter monitoring and ii) providing a starting point for researchers and water managers approaching this topic. This work supports the selection and design of reliable and cost-effective monitoring approaches to mitigate the ambiguity in macroplastic data collection, contributing to the global harmonization of macroplastic litter monitoring protocols
How could 50 °C be reached in Paris: Analyzing the CMIP6 ensemble to design storylines for adaptation
No full textInternational audienceReaching a surface temperature of 50 °C in a heavily populated region, like Paris, would have devastating effects. Although such a high value seems far from the present-day record of 42.6 °C, its occurrence cannot be dismissed by the end of the 21st century, due to the continuous increase of global mean temperature. In this paper, we address two questions that were asked by the City of Paris to a group of scientists: When does this event start to be likely? What are the prevailing meteorological conditions? We base our study on the CMIP6 simulation ensemble. Many of the CMIP6 yield biases in temperature. Rather than using methods of bias correction, which are not necessarily adapted to high extremes, we propose a pragmatic approach of model selection in order to seek such high temperature events that are deemed realistic. We analyze the meteorological conditions leading to first occurrences of such hot events and their common atmospheric patterns. This paper describes a simple data mining approach (on a large ensemble of climate model simulations) which could be adapted to other regions of the world, in order to help decision makers anticipating and adapting to such devastating meteorological events