Publications

La plupart des informations présentées ci-dessous ont été récupérées via RePEc avec l'aimable autorisation de Christian Zimmermann
US churches' response to Covid-19: Results from FacebookJournal articleEva Raiber et Paul Seabright, Covid Economics, Volume 61, pp. 121-171, 2020

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

How French general practitioners respond to declining medical density: a study on prescription practices, with an insight into opioids useJournal articleJulien Silhol, Bruno Ventelou et Anna Zaytseva, The European Journal of Health Economics, Volume 21, Issue 9, pp. 1391-1398, 2020

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.

Unconventional monetary policy reaction functions: evidence from the USJournal articleLuca Agnello, Vitor Castro, Gilles Dufrénot, Fredj Jawadi et Ricardo M. Sousa, Studies in Nonlinear Dynamics & Econometrics, Volume 24, Issue 4, pp. pp18, 2020

We specify unconventional monetary policy reaction functions for the Fed using linear and nonlinear econometric frameworks. We find that nonstandard policy measures are largely driven by the dynamics of inflation and the output gap, with the effect being particularly strong during QE rounds. Moreover, we uncover the presence of asymmetry and regime dependence in central bank’s actions since the global financial crisis, especially concerning the response of the term spread and the shadow short rate to the growth rate of central bank reserves. From a policy perspective and given the lack of a systematic response of monetary policy to asset price growth in nonstandard times, our findings seem to corroborate the view that concerns about asset price bubbles, financial sector pro-cyclicality and systemic risk should be part of the macro-prudential policy toolkit.

Equilibrium versions of set-valued variational principles and their applications to organizational behaviorJournal articleJing-Hui Qiu, Antoine Soubeyran et Fei He, Optimization, Volume 69, Issue 12, pp. 2657-2693, 2020

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.

Threshold regressions for the resource curseJournal articleNicolas Clootens et Djamel Kirat, Environment and Development Economics, Volume 25, Issue 6, pp. 583-610, 2020

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.

Évaluation économique de la mortalité liée à la pollution atmosphérique en FranceJournal articleOlivier Chanel, Sylvia Medina et Mathilde Pascal, Journal de gestion et d'Economie de la santé, Volume 38, Issue 2, pp. 77-92, 2020

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.

Convergence of GDP per capita in advanced countries over the twentieth centuryJournal articleAntonin Bergeaud, Gilbert Cette et Rémy Lecat, Empirical Economics, Volume 59, Issue 5, pp. 2509-2526, 2020

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.

Les communs. Des jardins partagés à wikipédiaBookJean-Benoît Zimmermann, 1000 Raisons, 2020-11, 220 pages, Libre & Solidaire, 2020

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.

Differences in work conditions between natives and immigrants: preferences vs. outside employment opportunitiesJournal articleEva Moreno Galbis, European Economic Review, Volume 130, pp. 103586, 2020

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.

Learning with minimal information in continuous gamesJournal articleSebastian Bervoets, Mario Bravo et Mathieu Faure, Theoretical Economics, Volume 15, Issue 4, pp. 1471-1508, 2020

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 equilibrium occurs in all locally ordinal potential games as soon as Nash equilibria are isolated.