Peer Effects, Fast Food Consumption and Adolescent Weight Gain

This paper aims at opening the black box of peer effects in adolescent weight gain. Using Add Health data on secondary schools in the U.S., we investigate whether these effects partly flow through the eating habits channel. Adolescents are assumed to interact through a friendship social network. We first propose a social interaction model of fast food consumption using a generalized spatial autoregressive approach. We exploit results by Bramoullé, Djebbari and Fortin (2009) which show that intransitive links within a network (i.e., a friend of one of my friends is not my friend) help identify peer effects. The model is estimated using maximum likelihood and generalized 2SLS strategies. We also estimate a panel dynamic weight gain production function relating an adolescent’s Body Mass Index (BMI) to his current fast food consumption and his lagged BMI level. Results show that there are positive significant peer effects in fast food consumption among adolescents belonging to a same friendship school network. The estimated social multiplier is 1.59. Our results also suggest that, at the network level, an extra day of weekly fast food restaurant visits increases BMI by 2.4%, when peer effects are taken into account.Obesity, overweight, peer effects, social interactions, fast food, spatial models

A Fuzzy Approach to the Measurement of Leakages for North American Health Systems

This paper uses a fuzzy-fuzzy stochastic dominance approach to compare patients’ leakages in the Canadian and the U.S. health care systems. Leakages are defined in terms of individuals who are in bad health and could not have access to health care when needed. To carry his comparison we rely on the assumption that Canada is a strong counterfactual for the U.S. We first develop a class of fuzzy leakages indices and incorporate them in a stochastic dominance framework to derive the dominance criterion. We then use the derived criterion to perform inter-country comparisons on the global level. To provide more insight, we decompose the analysis with respect to gender, ethnicity, income and education. Intra-country comparisons reveal the presence of income based leakage inequalities in both countries yet, gender, ethnic and education based disparities appear to be present in the U.S. only. As for inter-country comparisons, results are in general consistent with the hypothesis that leakages are less important under the Canadian health care system.Health care resources, Fuzzy sets, Leakage

Equivalence Scales and Housing Deprivation Orderings: An Example Using Lebanese Data

Housing deprivation orderings raise challenges as far as measurement is concerned. The first challengeresides in the identification of an adequate variable that characterizes housing services consumed byhouseholds. Another challenge may arise in the comparisons of housing services consumption betweenhouseholds of different sizes and composition. The last challenge may arise in the choice of a deprivationline and of a deprivation index. In this paper we address theoretically those challenges. An empirical illustration is offered using Lebanese data.Housing, Deprivation, Stochastic dominance, Equivalence scales, Lebanon

Equivalence Scales and Housing Deprivation Orderings: an Example Using Lebanese Data

Housing deprivation orderings raise challenges as far as measurement is concerned. The first challenge resides in the identification of an adequate variable that characterizes housing services consumed by households. Another challenge may arise in the comparisons of housing services consumption between households of different sizes and composition. The last challenge may arise in the choice of a deprivation threshold and of a deprivation index. In this paper we address theoretically those challenges. An empirical illustration is offered using Lebanese data.Housing, Deprivation, Stochastic dominance, Equivalence scales, Lebanon

A Fuzzy Approach to the Measurement of Leakages for North American Health Systems

This paper uses a fuzzy-fuzzy stochastic dominance approach to compare patients' leakages in the Canadian and the U.S health care systems. Leakages are defined in terms of individuals who are in bad health and could not have access to health care when needed. To carry this comparison we rely on the assumption that Canada is a strong counterfactual for the U.S. We first develop a class of fuzzy leakages indices and incorporate them in a stochastic dominance framework to derive the dominance criterion. We then use the derived criterion to perform inter-country comparisons on the global level. To provide more insight, we decompose the analysis with respect to gender, ethnicity, income and education. Intra-country comparisons reveal the presence of income based leakage inequalities in both countries yet, gender, ethnic and education based disparities appear to be present in the U.S only. As for inter-country comparison, results are in general consistent with the hypothesis that leakages are less important under the Canadian health care system.Health care resources, Fuzzy sets, Leakage

Three essays in health economics

L'objectif principal de cette thèse est de comprendre comment les interactions sociales peuvent affecter l'état de santé via des changements dans certains comportements. Trois raisons motivent l'intérêt pour cette question. Premièrement, des habitudes de vie telles que les mauvaises habitudes alimentaires ou le manque d'activité physique représentent un facteur de risque important pour la santé et donc une source de coûts qui pourraient être évités. Deuxièmement, il s'agit de mieux comprendre la façon dont certains problèmes affectent le capital santé des jeunes. Troisièmement, les interactions sociales qui influencent certains comportements sont une source d'externalités qui amplifient l'impact de chocs sur la santé, nécessitant ainsi l'adoption de politiques appropriées. Dans le premier essai, nous analysons l'épidémie d'obésité observée chez les jeunes américains. Ce problème a fait couler beaucoup d'encre récemment. La plupart des recherches publiées sur ce sujet étudient l'aspect socialement contagieux de l'obésité mais sans en expliquer les mécanismes. Dans un premier temps, nous allons au delà de cette approche pour analyser si la présence d'une telle épidémie sociale est due à des effets de pairs dans les habitudes alimentaires. Nous mettons en particulier l'accent sur la consommation de malbouffe. Dans un deuxième temps, nous examinons l'impact de cette consommation sur la dynamique des gains de poids. Dans le deuxième essai, nous nous intéressons à un second mécanisme de contagion sociale, soit les interactions sociales dans la pratique d'activités physiques chez les jeunes américains. A cet effet, nous évaluons d'abord la présence d'effets de pairs sur ces comportements chez les adolescents. Nous estimons ensuite l'impact de l'activité physique sur leur état de santé. Le troisième essai porte sur l'impact d'un régime relativement généreux de pension de vieillesse sur la santé des enfants en Afrique du Sud. Nous étudions en particulier si les effets attribués à ce programme sont dus à des changements comportementaux se traduisant par une augmentation de la cohabitation entre personnes Egées prestataires de la pension et les jeunes enfants

Detection and characterization of single nanoparticles using low-aspect-ratio silicon nitride nanopores

Nanopore-based single nanoparticle detection methods have found recently increasing importance in applications ranging from gaining a better understanding of biophysical processes to technology-driven solutions such as biomolecule sensing and nanoparticle characterization. The significant advantages of nanopores include label-free, high throughput, and low material requirement. However, challenges remain especially in terms of further improving sensitivity and specificity of such methods, which are the two most important factors to take into account for biomolecule/particle sensing. This work aims to improve nanopore-based nanoparticle sensing. We first use nanopore resistive pulse sensing to detect translocation of nanobeads through low-aspect-ratio silicon nitride nanopores. Resistive-pulse sensing utilizes the principle that a single particle in a pore filled with conductive solution decreases the ionic conductance of the orifice. Transit of the particle through the pore is observed as a dip in the ionic current. We used this principle to detect 50 and 100 nm polystyrene particles modified with carboxyl group. Our result shows that the translocation current of these two nanoparticles are different, and the translocation frequency increases non-linearly with the nanoparticle concentration. We also found that often translocating particles become permanently stuck onto the nanopore surface, causing the experiment to end prematurely. In the second half of this thesis, we present a new nanopore-based sensing method that does not only overcome the clogging limitation, but actually exploits the ionic current change and induced Brownian noise caused by the blockage to characterize the properties of single nanoparticles. The technique consists of electrokinetically trapping and de-trapping of particles near a nanopore, which happens when the diameter of the nanopore is smaller than that of the particles. We prove that trapping occurs due to a balance between two counteracting factors: electrophoretic and electroosmotic forces. The motion of the trapped nanoparticle can then be modeled as a damped harmonic oscillator. We use the new trapping phenomenon to characterize nanoparticles with different sizes and charges, each of which gives different blockage current and spring constant. We also study the dependence of applied voltage on the blockage current and spring constant, which shows the ability to tune the position of trapping and force exerted on the nanoparticle. This new technique may find applications in drug delivery, transport control, and biosensing

Egypt: Towards an Algerian scenario

It is hard to watch the events unfolding in Egypt today without drawing a parallel with the Algerian situation in 1990. The images of demonstrations and clashes between Egyptian security forces and the Muslim Brotherhood are eerily reminiscent of those carried out by the Algerian People’s National Army (APNA) against the Islamists and supporters of the Islamic Salvation Front (FIS). Will history repeat itself, in Egypt this time

Validation and application of agent-based electric vehicle charging model

Agent-based models are a class of simulation in which many autonomous agents interact such that the mix of stochastic and deterministic actions each agent undertakes results in some emergent behaviour across the entire population. Such models have been used to explore the impacts of electric vehicles (EVs) on electricity grids. However, there has been little data available against which to validate this approach. In this study, we evaluate an agent based EV model against real data observed during the “My Electric Avenue” project; an Ofgem funded 3 year trial aiming to identify the impacts of EVs on local grids. We find that, within the constraints of the available trial data, the agent model is able to replicate dominant charging pattern features. The behaviour of owners will inevitably play a role in the actual charging patterns observed and we further explore how consumer adoption of time-of-use tariffs and vehicle range (battery capacity) preference would impact on demands at the local substation. We show that simplistic adoption of time-of-use tariffs would have undesirable consequences for network peak demands and that the expected increase in EV range and thus battery size, will both increase peaks and total energy supply to domestic properties

Peer Effects, Fast Food Consumption and Adolescent Weight Gain

This paper aims at opening the black box of peer effects in adolescent weight gain. Using Add Health data on secondary schools in the U.S., we investigate whether these effects partly flow through the eating habits channel. Adolescents are assumed to interact through a friendship social network. We first propose a social interaction model of fast food consumption using a generalized spatial autoregressive approach. We exploit results by Bramoullé, Djebbari and Fortin (2009) which show that intransitive links within a network (i.e., a friend of one of my friends is not my friend) help identify peer effects. The model is estimated using maximum likelihood and generalized 2SLS strategies. We also estimate a panel dynamic weight gain production function relating an adolescent’s Body Mass Index (BMI) to his current fast food consumption and his lagged BMI level. Results show that there are positive significant peer effects in fast food consumption among adolescents belonging to a same friendship school network. The estimated social multiplier is 1.59. Our results also suggest that, at the network level, an extra day of weekly fast food restaurant visits increases BMI by 2.4%, when peer effects are taken into account. Cet article a pour but d’ouvrir la boîte noire des effets de pairs dans les gains de poids chez les adolescents. À partir des données Add Health sur les écoles secondaires aux États-Unis, nous étudions si ces effets découlent en partie des habitudes alimentaires. On suppose que les adolescents interagissent dans le cadre d’un réseau social d’amitié. Nous proposons une analyse des interactions sociales de consommation de malbouffe à l’aide d’un modèle autorégressif spatial généralisé. Nous exploitons les résultats de Bramoullé, Djebbari et Fortin (2009) qui montrent que les liens intransitifs à l’intérieur d’un réseau (i.e., un ami d’un de mes amis n’est pas mon ami) aide à l’identification des effets de pairs. Le modèle est estimé à partir de méthodes de maximum de vraisemblance et de variables instrumentales généralisées. Nous estimons en outre une fonction dynamique de gain de poids reliant l’indice de masse corporelle de l’adolescent (IMC) à sa consommation courante de malbouffe et à son niveau retardée d’IMC. Nos résultats montrent qu’il existe des effets de pairs positifs et significatifs dans la consommation de malbouffe parmi les adolescents appartenant au même réseau d’amis de l’école. Le multiplicateur social est de 1,59. Nos résultats suggèrent de plus qu’au niveau du réseau social, une journée additionnelle de consommation hebdomadaire dans un restaurant de malbouffe augmente l’IMC de 2,4 %, lorsque les effets de pairs sont pris en compte.Obesity, overweight, peer effects, social interactions, fast food, spatial models., Obésité, embompoint, effets de pair, malbouffe, réseaux sociaux, modèle autorégressif spatial