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Heterogeneous peer effects and gender-based interventions for teenage obesity
No full textInternational audienceThis paper explores the role of gender heterogeneity in the social diffusion of obesity among adolescents and its policy implications. We propose a social interaction model which allows for gender-dependent heterogeneity in peer effects. Our empirical approach is consistent with the best response functions of a non-cooperative model where social interactions stem from the channel of pure spillover or pure conformity. We estimate the model using data on adolescent Body Mass Index and network-based interactions. Our approach allows us to account for network endogeneity. Our results show that peer effects are gender-dependent, and male students are particularly responsive to the weight of their female friends. According to simulations, reaching out to women results in an 8% increase in effectiveness in reducing overall BMI, based on the most conservative scenario. Thus, female-tailored interventions are likely to be more effective than a gender-neutral approach to fighting obesity in schools
What Makes a Satisfying Life? Prediction and Interpretation with Machine‐Learning Algorithms
No full textInternational audienceMachine Learning (ML) methods are increasingly being used across a variety of fields, and have led to the discovery of intricate relationships between variables. We here apply ML methods to predict and interpret life satisfaction using data from the UK British Cohort Study. We discuss the application of first Penalized Linear Models and then one non‐linear method, Random Forests. We present two key model‐agnostic interpretative tools for the latter method: Permutation Importance and Shapley Values. With a parsimonious set of explanatory variables, neither Penalized Linear Models nor Random Forests produce major improvements over the standard Non‐penalized Linear Model. However, once we consider a richer set of controls these methods do produce a non‐negligible improvement in predictive accuracy. Although marital status, and emotional health continue to be the most‐important predictors of life satisfaction, as in the existing literature, gender becomes insignificant in the non‐linear analysis
Littératie financière : le « mauvais » genre ?
No full textInternational audienceThe concept of “financial literacy” has become a must when studying household finance. All empirical studies show that, overall, people’s financial knowledge is rather limited, particularly in certain categories of the population, notably among women. This article examines the gender gap in France. The gap seems to be better accounted for by social norms, gender stereotypes, or preferences than by observable individual characteristics. A financial education policy aimed at improving literacy must therefore be differentiated according to gender.Le concept de « financial literacy » est, aujourd’hui, un point de passage obligé, afin d’étudier la finance des ménages. Toutes les études empiriques montrent que, globalement, les connaissances financières des individus sont plutôt limitées, particulièrement dans certaines catégories de la population, notamment chez les femmes. Cet article fait le point sur ce gender gap, dans le cas de la France. Cet écart semble davantage expliqué par les normes sociales, les stéréotypes de genre, ou encore les préférences, que par les caractéristiques observables des individus. Une politique d’éducation financière, visant à améliorer la littératie, doit donc être différenciée selon le sexe
Lessons for Interactive Theorem Proving Researchers from a Survey of Coq Users
No full textInternational audienceThe Coq Community Survey 2022 was an online public survey of users of the Coq proof assistant conducted during February 2022. Broadly, the survey asked about use of Coq features, user interfaces, libraries, plugins, and tools, views on renaming Coq and Coq improvements, and also demographic data such as education and experience with Coq and other proof assistants and programming languages. The survey received 466 submitted responses, making it the largest survey of users of an interactive theorem prover (ITP) so far. We present the design of the survey, a summary of key results, and analysis of answers relevant to ITP technology development and usage. In particular, we analyze user characteristics associated with adoption of tools and libraries and make comparisons to adjacent software communities. Notably, we find that experience has significant impact on Coq user behavior, including on usage of tools, libraries, and integrated development environments (IDEs)
The End of Londongrad? Ownership transparency and Offshore Investment in Real Estate
No full textThis paper studies the impact of beneficial ownership transparency in the British real estate market. In an effort to reduce illicit investment following the invasion of Ukraine, the UK government announced a new law in 2022 requiring offshore companies that owned domestic real estate to identify their ultimate owners in a public register. Using a difference-in-difference framework, we find that new property purchases by companies registered in tax havens fell relative to those made via non-havens, a result consistent with transparency raising the costs of illicit investment. These declines persist even after dropping tax havens favored by Russians, suggesting that the reform drove the decline, rather than sanctions. We do not find strong evidence of price effects nor substitution into ownership through suspicious domestic companies. While the policy does appear to have been effective at deterring some anonymous investment into the British property market, incomplete implementation led some clients to still successfully shield their ownership information, implying scope for better design and enforcement in the future
Media Coverage of Immigration and the Polarization of Attitudes
No full textInternational audienceThis paper investigates the effect of media coverage on immigration attitudes. It combines data on immigration coverage in French television with individual panel data from 2013 to 2017 that records respondents' preferred television channel and attitudes toward immigration. The analysis focuses on within-individual variations over time, addressing ideological self-selection into channels. We find that increased coverage of immigration polarizes attitudes, with initially moderate individuals becoming more likely to report extremely positive and negative attitudes. This polarization is mainly driven by an increase in the salience of immigration, which reactivates pre-existing prejudices, rather than persuasion effects from biased news consumption
Prudent aggregation of quasi-hyperbolic experts
No full textInternational audienceImagine a cohort of economic experts appraising long-term projects through the quasi-hyperbolic discounting criterion. The parameters (long-run and short-run discount rates) used by each expert may differ, which implies different policy recommendations. Subsequently, a decision maker is faced with the task of selecting an efficient aggregation from these varied opinions. This paper proposes a solution to reconcile these conflicting recommendations, taking into account the decision maker’s adoption of a “prudent” behavior
L’ expérimentation « Territoires zéro chômeur de longue durée » : analyse quantitative des entreprises à but d’emploi et de leurs salariés
No full textL’expérimentation « Territoires zéro chômeur de longue durée » vise en priorité à proposer des emplois adaptés aux personnes durablement privées d’emploi résidant sur les territoires concernés par l’expérimentation.Ce rapport est composé de deux chapitres qui étudient deux aspects différents du programme « Territoires zéro chômeur de longue durée » (TZCLD). Le premier chapitre est centré sur le fonctionnement des entreprises à but d’emploi (EBE), en particulier en ce qui concerne leurs résultats économiques et l’impact qu’elles ont sur le tissu productif local. Le deuxième chapitre présente les résultats d’une enquête menée auprès des salariés en EBE, portant principalement sur leur état de santé et leur bien-être. Les réponses collectées sont comparées à celles d’un groupe témoin comparable
Détecteur diamant pour la détection de particules à faible parcours: Membrane diamant pour le monitorage en ligne de microfaisceaux d'ions et télescope ΔE-E pour l'identification de particules
No full textThe work described in this thesis focuses on the development of innovative diamond detectors. They are designed to detect short-range particles for use in support of radiobiology and nuclear physics applications. Diamond, a wide bandgap semiconductor, was chosen for its qualities in terms of charge transport and collection (high carrier mobility and high saturation velocity). The physical analyses and technical developments carried out focused on the geometry and arrangement of the different diamond layers used in the detectors, in order to adapt them to the scientific issues addressed in the study. This manuscript is divided into two main sections. The first part deals with the online monitoring of air-extracted ion microbeams which are capable of irradiating biological samples on a micrometric scale in order to study post-irradiation cellular mechanisms. This requires the development of a sufficiently thin detector that allows low-energy ions (from a few hundred keV to a few MeV) to pass through it during biological irradiation. Thus, membranes a few microns thick were conceived using a deep diamond etching protocol. The aim is to obtain a highly homogeneous surface with very low roughness for optimal charge collection. Plasma etching was chosen because it allowed speeds of a few micrometres per hour to be achieved. Comparisons between different etching settings are presented. The use of polycrystalline diamond masks made it possible to obtain etching patterns adapted to the mechanical constraints (vacuum-air interface) associated with the use of membranes as active windows for extracting beams into the air before they impact biological cultures (ion counting). A prototype comprising four membranes with an average thickness of 7.6 µm was produced. Its response was fully characterised under proton beams at the AIFIRA facility at LP2I Bordeaux. In the second part of the manuscript, a monolithic diamond ΔE-E telescope, a second prototype designed to improve on previous work, was fully characterised under ion and electron beams. With such a device, the measurement of energy deposits in two successive stages, ΔE and E, makes it possible to deduce the identity of the incident particle (atomic number and mass). The objective of designing such a device is to obtain a detector that combines compactness and charge collection efficiency. The distinctive feature of this detector lies in the superposition of intrinsic diamond layers and diamond layers heavily doped with boron. The detector was sized so that it could be tested with a wide range of incident particles to establish proof of concept. The results of its characterisation under low-energy electron beams (30~keV), protons (up to 3~MeV), carbon (0.98~MeV/u) and alpha particles from an source are presented and discussed.Les travaux décrits au cours de cette thèse portent sur le développement de détecteurs diamant innovants destinés à la détection de particules à faible parcours pour des applications en support à la radiobiologie et à la physique nucléaire. Le diamant, semi-conducteur à grand gap, a été choisi pour ses qualités en termes de transport et collecte de charges (importantes mobilités des porteurs ainsi que vitesses de saturation élevées). Pour l’adapter aux problématiques scientifiques de l’étude, la géométrie et l’arrangement de différentes couches de diamant entrant dans la réalisation des détecteurs ont été les points centraux des analyses physiques et développement techniques réalisés. Ce manuscrit est divisé en deux parties. La première porte sur le monitorage en ligne de microfaisceaux d’ions extraits à l’air capable d’irradier des échantillons biologiques à l’échelle micrométrique pour étudier les mécanismes cellulaires post-irradiation. Cela nécessite la réalisation d’un détecteur suffisamment fin qui permette à des ions de basse énergie (de quelques centaines de keV à quelques MeV) de le traverser lors d’irradiations biologiques. Ainsi, des membranes de quelques microns d’épaisseur ont été conçues par la mise en œuvre d’un protocole de gravure profonde du diamant avec pour objectif l’obtention d’une surface d’une grande homogénéité avec une très faible rugosité pour une collecte de charge optimale. La gravure plasma a été retenue car elle a permis d’atteindre des vitesses de quelques micromètres par heure. Des comparaisons entre différents paramétrages de gravure sont présentés. L’utilisation de masques en diamant polycristallin a permis d’obtenir les motifs de gravures adaptés aux contraintes mécaniques (interface vide – air) liée à l’utilisation des membranes comme fenêtre active d’extraction des faisceaux à l’air avant impact sur les cultures biologiques (comptage des ions). Un prototype comportant quatre membranes d’épaisseur moyenne de 7,6~µm a été réalisé. Sa réponse a été caractérisée entièrement, sous faisceaux de protons sur l’installation AIFIRA du LP2I Bordeaux. En deuxième partie du manuscrit, un télescope E-E monolithique en diamant, second prototype conçu en amélioration de travaux antérieurs, a été entièrement caractérisé sous faisceaux d’ions et d’électrons. Avec un tel dispositif, la mesure des dépôts d’énergies dans deux étages successifs, E et E, permet de déduire l’identité de la particule incidente (nombre atomique et masse). L’objectif lié à la conception d’un tel dispositif est d’obtenir un détecteur mêlant compacité et efficacité de collecte de charges. La particularité de ce détecteur réside dans la superposition de couches de diamant intrinsèque et de diamant fortement dopée en bore. Le détecteur a été dimensionné afin de pouvoir être testé avec un large panel de particules incidentes pour en établir la preuve de concept. Les résultats issus de sa caractérisation sous faisceaux d’électrons de faible énergie (30~keV), de protons (jusqu’à~3 MeV), de carbone (0,98~MeV/u) et d’alpha issus de source sont présentées et discutés
Political Brinkmanship and Compromise
No full textInternational audienceWe study how do-or-die threats ending negotiations affect gridlock and welfare when two opposing parties bargain. Failure to agree on a deal in any period implies a continuation of the negotiation. However, under brinkmanship, agreement failure in any period may precipitate a crisis with a small chance, i.e. an outcome worse than the status-quo and any possible deal. In equilibrium, such brinkmanship threats improve the probability of an agreement but also increase the risk of crisis. Brinkmanship reduces welfare when one might think it is most needed: severe gridlock. In this case, despite this global welfare loss, a party has incentives to use brinkmanship strategically to obtain a favorable bargaining position