Publications

Résumé In this article we propose a theoretical model to better comprehend the effect of gun laws on violent property crime. We assume that a violent encounter between a criminal and a victim is costly to both, and we uncover two types of equilibria: a pure strategy violent equilibrium and a mixed strategy equilibrium where the criminal is deterred with strictly positive probability. The effect of a relaxation of gun laws is shown to be conditional on both initial gun laws and on the relative improvement of the victims’ defense capacity relative to the criminals’ offense capacity. We uncover a potentially inverted U-shaped relationship between gun laws leniency and investments in violent activities which helps reconciling seemingly contradictory empirical findings.
Mots clés Deterrence, Gun laws, Crime, Dissuasion, Contrôle des armes à feu, Crime
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Résumé By using a pre-order principle in [Qiu JH. A pre-order principle and set-valued Ekeland variational principle. J Math Anal Appl. 2014;419:904–937], we establish a general equilibrium version of set-valued Ekeland variational principle (denoted by EVP), where the objective function is a set-valued bimap defined on the product of left-complete quasi-metric spaces and taking values in a quasi-ordered linear space, and the perturbation consists of a cone-convex subset of the ordering cone multiplied by the quasi-metric. Moreover, we obtain an equilibrium EVP, where the perturbation contains a σ-convex subset and the quasi-metric. From the above two general EVPs, we deduce several interesting corollaries, which extend and improve the related known results. Several examples show that the obtained set-valued EVPs are new. Finally, applying the above EVPs to organizational behavior sciences, we obtain some interesting results on organizational change and development with leadership. In particular, we show that the existence of robust organizational traps.
Mots clés Robust trap problem, Caristi&#039, s fixed point theorem, Pre-order principle, Quasi-metric space, Equilibrium version of Ekeland variational principle
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Résumé Disparities in physicians' geographical distribution lead to highly unequal access to healthcare, which may impact quality of care in both high and low-income countries. This paper uses a 2013-2014 nationally representative survey of French general practitioners (GPs) matched with corresponding administrative data to analyze the effects of practicing in an area with weaker medical density. To avoid the endogeneity issue on physicians' choice of the location, we enriched our variable of interest, practicing in a relatively underserved area, with considering changes in medical density between 2007 and 2013, thus isolating GPs who only recently experienced a density decline (identifying assumption). We find that GPs practicing in underserved areas do shorter consultations and tend to substitute time-consuming procedures with alternatives requiring fewer human resources, especially for pain management. Results are robust to considering only GPs newly exposed to low medical density. Findings suggest a significant impact of supply-side shortages on the mix of healthcare services used to treat patients, and point to a plausible increased use of painkillers, opioids in particular.
Mots clés France, Opioids, Health workforce, Medically underserved area, General practitioners, Prescriptions
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Résumé In this paper, we study insurance decisions when the policyholder evaluates insurance with narrow framing. We show that due to aversion to risk on the net insurance payoff, i.e., insurance indemnity minus insurance premium, narrow framing reduces insurance demand. This helps explaining the observed low insurance demand in many insurance markets. We also show that the optimal insurance contract involves a deductible and the coinsurance of losses above the deductible when transaction costs depend on the actuarial value of the policy. Moreover, when the policyholder is loss averse over the net insurance payoff, a fixed indemnity equal to insurance premium should be paid for a range of intermediate losses.
Mots clés Deductible Hedging Risk sharing Narrow framing Loss aversion
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Résumé Fêtes de réveillon en petit comité ou annulées, familles dispersées et isolées, autoconfinement, confinements locaux, partiels ou généralisés, couvre-feu, restrictions de déplacement, fermeture des frontières, incertitudes quant à la réouverture de certains secteurs : la France, comme de nombreux autres pays du monde, a fait face à une série de restrictions pour tenter d'endiguer l'épidémie. Si chaque type de mesures/restrictions a sa propre efficacité dans le contrôle de la dynamique épidémiologique, ces dernières doivent également être évaluées en fonction de leur acceptabilité par la population. À l'heure où les décideurs se posent la question de ré-évaluer les mesures restrictives pour éviter un rebond de l'épidémie, les préférences des populations devraient compter dans la décision publique.
Mots clés Confinement, Epidémie de Covid-19, Mesure restrictive
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Résumé This paper analyzes the behavior of cross-country growth rates with respect to resource abundance and dependence. We reject the linear model that is commonly used in growth regressions in favor of a multiple-regime alternative. Using a formal sample-splitting method, we find that countries exhibit different behaviors with respect to natural resources depending on their initial level of development. In high-income countries, natural resources play only a minor role in explaining the differences in national growth rates. On the contrary, in low-income countries, abundance seems to be a blessing but dependence restricts growth.
Mots clés Natural resources, Threshold regressions, Growth, Resource curse
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Résumé This study investigates U.S. churches' response to the SARS-CoV-2 pandemic by looking at their public Facebook posts. For religious organizations, in-person gatherings are at the heart of their activities. Yet religious in-person gatherings have been identified as some of the early hot spots of the pandemic, but there has also been controversy over the legitimacy of public restrictions on such gatherings. Our sample contains information on church characteristics and Facebook posts for nearly 4000 churches that posted at least once in 2020. The share of churches that offer an online church activity on a given Sunday more than doubled within two weeks at the beginning of the pandemic (the first half of March 2020) and stayed well above baseline levels. Online church activities are positively correlated with the local pandemic situation at the beginning, but uncorrelated with most state interventions. After the peak of the first wave (mid April), we observe a slight decrease in online activities. We investigate heterogeneity in the church responses and find that church size and worship style explain differences consistent with churches facing different demand and cost structures. Local political voting behavior, on the other hand, explains little of the variation. Descriptive analysis suggests that overall online activities, and the patterns of heterogeneity, remain unchanged through end-November 2020.
Mots clés Social media, Church, Covid-19 pandemic, Facebook
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Résumé This paper analyzes the link between asset bubbles, endogenous labor and capital. First, we explicitly and theoretically derive the conditions to have a crowding-in effect of the bubble, i.e. higher levels of capital and labor. Second, the utility function we consider shows that this result does not require an arbitrarily high elasticity of intertemporal substitution in consumption.
Mots clés Overlapping generations, Endogenous labor, Crowding-in effect, Asset bubbles
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Résumé This study compares GDP per capita levels and growth rates across 17 advanced economies over the period 1890–2013 using an accounting breakdown and runs Phillips and Sul (Econometrica 75(6):1771–1855, 2007) convergence tests. An overall convergence process has been at work among advanced economies, mainly after WWII, driven mostly by capital intensity and then TFP, while trends in hours worked and employment rates are disparate. However, this convergence process came to a halt during technology shocks, during the two world wars and since the 1990s, with the convergence of advanced economies stopping far from the level of US GDP per capita.
Mots clés Global history, Technological change, Convergence, Productivity, GDP per capita
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Résumé Immigrants are disproportionately employed in agriculture and construction, sectors with relatively high injury rates. What pushes immigrants to accept riskier and more strenuous work conditions? We propose a circular model and show that differences in average work conditions borne by natives and immigrants are driven by both preferences and unearned income. Using French data we find that, in line with the model’s predictions, (i) rigid wages are associated with a larger immigrant-native gap in work conditions; (ii) high unearned income individuals benefit on average from better work conditions; (iii) for immigrants and natives with high unearned income, differences in demographic characteristics explain part of the immigrant-native gap in work conditions. In contrast, the gap largely persists among low unearned income people even once we have imposed identical demographic composition among them. This suggests that there must be other factors that influence preferences over work conditions and that are missing in our empirical analysis.
Mots clés Composition effects, Preferences, Outside employment opportunities, Work conditions, Immigrants
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Résumé This paper provides an empirical assessment of the effect of income inequality on credit dynamics in 12 advanced economies over the period 1948-2015. We use foreign Communist influence as an instrument to identify exogenous variation in inequality and estimate the dynamic effect of a top income shock on credit over GDP. The results suggest that the evolution of top incomes has persistent effects on credit expansion, especially for mortgage and business loans.
Mots clés Top income shares, Income inequality, Finance, Credit
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Résumé Cet article propose une discussion méthodologique à partir d’une évaluation économique des impacts sur la mortalité de l’exposition chronique aux particules fines en France continentale. Il prend comme point de départ l’évaluation quantitative d’impact sanitaire (EQIS), réalisée par Santé publique France en 2016, de 5 scénarios de réduction des concentrations par deux méthodes de mesure de la mortalité (nombre de décès prématurés évités et nombre total d’années de vie gagnées). Après une justification des valeurs monétaires utilisées – 3 millions € pour la valeur d’évitement d’un décès et 80 000 € pour celle d’une année de vie gagnée – nous les appliquons aux données sanitaires, et obtenons des résultats comparables aux études contemporaines. En particulier, dans un scénario sans pollution anthropique, l’EQIS de 2016 estime à 48 283 les décès prématurés évités, que nous évaluons à 144,85 milliards €2008. Nous questionnons ensuite les méthodes et pratiques, en commençant par identifier les sources de divergence avec la précédente étude française menée en 1998-99, dont l’évaluation était 5 fois moindre en dépit d’émissions particulaires plus élevées. Puis, nous discutons le choix des valeurs monétaires et les conditions d’utilisation de ces résultats dans la décision publique. Au final, nous apportons un argument supplémentaire sur la nécessité de réduire l’exposition des populations à la pollution de l’air ambiant en France.
Mots clés Value of a prevented fatality, Mortality, Economic valuation, Air pollution, Valeur d&#039, évitement d&#039, un décès, Pollution atmosphérique, Évaluation économique, Mortalité
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Résumé This paper provides experimental support for the hypothesis that insurance can be a motive for religious donations. We randomize enrollment of members of a Pentecostal church in Ghana into a commercial funeral insurance policy. Then church members allocate money between themselves and a set of religious goods in a series of dictator games with significant stakes. Members enrolled in insurance give significantly less money to their own church compared to members that only receive information about the insurance. Enrollment also reduces giving towards other spiritual goods. We set up a model exploring different channels of religiously based insurance. The implications of the model and the results from the dictator games suggest that adherents perceive the church as a source of insurance and that this insurance is derived from beliefs in an interventionist God. Survey results suggest that material insurance from the church community is also important and we hypothesize that these two insurance channels exist in parallel.
Mots clés Charitable giving, Informal Insurance, Economics of religion
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Résumé While payoff-based learning models are almost exclusively devised for finite action games, where players can test every action, it is harder to design such learning processes for continuous games. We construct a stochastic learning rule, designed for games with continuous action sets, which requires no sophistication from the players and is simple to implement: players update their actions according to variations in own payoff between current and previous action. We then analyze its behavior in several classes of continuous games and show that convergence to a stable Nash equilibrium is guaranteed in all games with strategic complements as well as in concave games, while convergence to Nash occurs in all locally ordinal potential games as soon as Nash equilibria are isolated.
Mots clés Stochastic approximation, Continuous games, Payoff-based learning
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Résumé Les communs, dont les racines historiques sont lointaines, ont toujours prouvé, au fil du temps, leur efficacité comme mode d'action collective et solidaire et sont aujourd'hui une réalité incontournable de ce début du XXIe siècle. Ils manifestent la volonté d'un nombre croissant de citoyens de reprendre la main sur leur destin, à l'heure où les grands centres de décision s'éloignent de leur vie quotidienne dans les contingences de la mondialisation économique et financière. Un commun, c'est un mode d'action collective autour d'une ressource partagée, pour la gérer efficacement au bénéfice de chacun et la préserver contre la dégradation ou une appropriation abusive. On trouve des communs dans une très grande variété de domaines : ressources naturelles et foncières, cognitives, sociales, urbaines... Des jardins partagés à Wikipedia, des AMAP aux monnaies locales, les initiatives collaboratives se multiplient. Les communs ne sont pas, comme certains de leurs détracteurs les qualifient, une naïve utopie débouchant sur une indescriptible pagaille dans laquelle chacun n'agirait qu'en fonction de son intérêt propre. Un commun, c'est aussi une gouvernance s'appuyant sur une structure et un système de règles, produites collectivement et acceptées par tous avec, pour chacun, des rôles différenciés en termes de droits et de responsabilités. Cet ouvrage a été rédigé avant la pandémie de la Covid-19. Or, par-delà le repli sur soi et la peur de l'autre, la crise sanitaire a aussi donné lieu à de magnifiques initiatives de solidarité et d'action collective. Elle a rappelé à quel point la problématique des communs, qui ouvre une troisième voie, hors de la dualité État/marché, est plus que jamais d'actualité. Ce livre propose une analyse des fondements du phénomène et de la variété de ses manifestations. Il interroge sur la question de savoir dans quelle mesure les communs peuvent constituer un moteur de transformation profonde de nos sociétés.
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Mots clés Stochastic Games
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Résumé This paper investigates the impact of informal microfinance groups (self-help groups, or SHGs) on children’s education and work in rural India. In 2002, 24 eligible villages were randomly selected for opening SHGs, and 12 others were randomly selected as a control group. Households were surveyed three times over a 5-year period, allowing for the study of medium-term outcomes. We find a robust and strong increase in secondary school enrollment rates over time, with intention-to-treat estimates of about 40%. This effect stems from a quicker grade progression, leading to lower dropout rates between primary and secondary school. Contrary to usual presumptions, we find no decrease in overall child labor (but a reorientation toward part-time domestic work) and no direct role of credit. By contrast, we show that social interactions within SHGs are very important.
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Résumé We consider a contracting relationship where the agent's effort induces monetary costs, and limits on the agent's resource restrict his capability to exert effort. We show that, the principal finds it best to offer a sharing contract while providing the agent with an up-front financial transfer only when the monetary cost is neither too low nor too high. Thus, unlike in the limited liability literature, the principal might find it optimal to fund the agent. Moreover, both incentives and the amount of funding are non-monotonic functions of the monetary cost. These results suggest that an increase in the interest rate may affect the form of contracts differently , depending on the initial level of the former. Using the analysis, we provide and discuss several predictions and policy implications.
Mots clés Funding, Wealth constraint, Moral hazard, Contract theory
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Résumé In game theory, the question of convergence of dynamical systems to the set of Nash equilibria has often been tackled. When the game admits a continuum of Nash equilibria, however, a natural and challenging question is whether convergence to the set of Nash equilibria implies convergence to a Nash equilibrium. In this paper we introduce a technique developed in Bhat and Bernstein (2003) as a useful way to answer this question. We illustrate it with the best-response dynamics in the local public good game played on a network, where continua of Nash equilibria often appear.
Mots clés Convergence, Continua of Nash equilibria, Best-response dynamics
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Résumé Objective: We assess the existence of unfair inequalities in health and death using the normative framework of inequality of opportunities, from birth to middle age in Great Britain. Methods: We use data from the 1958 National Child Development Study, which provides a unique opportunity to observe individual health from birth to the age of 54, including the occurrence of mortality. We measure health status combining self-assessed health and mortality. We compare and statistically test the differences between the cumulative distribution functions of health status at each age according to one childhood circumstance beyond people's control: the father's occupation. Results: At all ages, individuals born to a 'professional', 'senior manager or technician' father report a better health status and have a lower mortality rate than individuals born to 'skilled', 'partly skilled' or 'unskilled' manual workers and individuals without a father at birth. The gap in the probability to report good health between individuals born into high social backgrounds compared with low, increases from 12 percentage points at age 23 to 26 at age 54. Health gaps are even more marked in health states at the bottom of the health distribution when mortality is combined with self-assessed health. Conclusions: There is increasing inequality of opportunities in health over the lifespan in Great Britain. The tag of social background intensifies as individuals get older. Finally, there is added analytical value to combining mortality with self-assessed health when measuring health inequalities.
Mots clés Mortality, Self-assessed health, Longitudinal, Health inequality, Equality of opportunity, Childhood
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