Publications

La plupart des informations présentées ci-dessous ont été récupérées via RePEc avec l'aimable autorisation de Christian Zimmermann
Targeting the key player: An incentive-based approachJournal articleMohamed Belhaj et Frédéric Deroian, Journal of Mathematical Economics, Volume 79, Issue C, pp. 57-64, 2018

We consider a network game with local complementarities. A policymaker, aiming at minimizing or maximizing aggregate effort, contracts with a single agent on the network to trade effort change against transfer. The policymaker has to find the best agent and the optimal contract to offer. Our study shows that for all utilities with linear best-responses, it only takes two statistics about the position of each agent on the network to identify the key player: the Bonacich centrality and the self-loop centrality. We also characterize key players under linear quadratic utilities for various contractual arrangements.

Testing for misspecification in the short-run component of GARCH-type modelsJournal articleThomas Chuffart, Emmanuel Flachaire et Anne Péguin-Feissolle, Studies in Nonlinear Dynamics & Econometrics, Volume 22, Issue 5, pp. 1-17, 2018

In this article, a misspecification test in conditional volatility and GARCH-type models is presented. We propose a Lagrange Multiplier type test based on a Taylor expansion to distinguish between (G)ARCH models and unknown GARCH-type models. This new test can be seen as a general misspecification test of a large set of GARCH-type univariate models. It focuses on the short-term component of the volatility. We investigate the size and the power of this test through Monte Carlo experiments and we compare it to two other standard Lagrange Multiplier tests, which are more restrictive. We show the usefulness of our test with an illustrative empirical example based on daily exchange rate returns.

TCR and CD28 Concomitant Stimulation Elicits a Distinctive Calcium Response in Naive T CellsJournal articleFan Xia, Cheng-Rui Qian, Zhou Xun, Yannick Hamon, Anne-Marie Sartre, Anthony Formisano, Sébastien Mailfert, Marie-Claire Phelipot, Cyrille Billaudeau, Sébastien Jaeger, et al., Frontiers in Immunology, Volume 9, 2018

T cell activation is initiated upon ligand engagement of the T cell receptor (TCR) and costimulatory receptors. The CD28 molecule acts as a major costimulatory receptor in promoting full activation of naive T cells. However, despite extensive studies, why naive T cell activation requires concurrent stimulation of both the TCR and costimulatory receptors remains poorly understood. Here, we explore this issue by analyzing calcium response as a key early signaling event to elicit T cell activation. Experiments using mouse naive CD4+ T cells showed that engagement of the TCR or CD28 with the respective cognate ligand was able to trigger a rise in fluctuating calcium mobilization levels, as shown by the frequency and average response magnitude of the reacting cells compared with basal levels occurred in unstimulated cells. The engagement of both TCR and CD28 enabled a further increase of these two metrics. However, such increases did not sufficiently explain the importance of the CD28 pathways to the functionally relevant calcium responses in T cell activation. Through the autocorrelation analysis of calcium time series data, we found that combined but not separate TCR and CD28 stimulation significantly prolonged the average decay time (τ) of the calcium signal amplitudes determined with the autocorrelation function, compared with its value in unstimulated cells. This increasement of decay time (τ) uniquely characterizes the fluctuating calcium response triggered by concurrent stimulation of TCR and CD28, as it could not be achieved with either stronger TCR stimuli or by coengaging both TCR and LFA-1, and likely represents an important feature of competent early signaling to provoke efficient T cell activation. Our work has thus provided new insights into the interplay between the TCR and CD28 early signaling pathways critical to trigger naive T cell activation.

Data from: Regional paleoclimates and local consequences: Integrating GIS analysis of diachronic settlement patterns and process-based agroecosystem modeling of potential agricultural productivity in Provence (France)Journal articleDaniel Contreras, Eneko Hiriart, Alberte Bondeau, Alan Kirman, Joël Guiot, Loup Bernard, Romain Suarez et Sander Van Der Leeuw, 2018

Holocene climate variability in the Mediterranean Basin is often cited as a potential driver of societal change, but the mechanisms of this putative influence are generally little explored. In this paper we integrate two tools - agro-ecosystem modeling of potential agricultural yields and spatial analysis of archaeological settlement pattern data - in order to examine the human consequences of past climatic changes. Focusing on a case study in Provence (France), we adapt an agro-ecosystem model to the modeling of potential agricultural productivity during the Holocene. Calibrating this model for past crops and agricultural practices and using a downscaling approach to produce high spatiotemporal resolution paleoclimate data from a Mediterranean Holocene climate reconstruction, we estimate realistic potential agricultural yields under past climatic conditions. These serve as the basis for spatial analysis of archaeological settlement patterns, in which we examine the changing relationship over time between agricultural productivity and settlement location. Using potential agricultural productivity (PAgP) as a measure of the human consequences of climate changes, we focus on the relative magnitudes of 1) climate-driven shifts in PAgP and 2) the potential increases in productivity realizable through agricultural intensification. Together these offer a means of assessing the scale and mechanisms of the vulnerability and resilience of Holocene inhabitants of Provence to climate change. Our results suggest that settlement patterns were closely tied to PAgP throughout most of the Holocene, with the notable exception of the period from the Middle Bronze Age through the Early Iron Age. This pattern does not appear to be linked to any climatically-driven changes in PAgP, and conversely the most salient changes in PAgP during the Holocene cannot be clearly linked to any changes in settlement pattern. We argue that this constitutes evidence that vulnerability and resilience to climate change are strongly dependent on societal variables.

Intra-household bargaining in poor countriesBook chapterJean-Marie Baland et Roberta Ziparo, In: Towards Gender Equity in Development, S. Anderson, L. Beaman et J.-P. Platteau (Eds.), 2018-11, pp. 69-96, Oxford University Press, 2018

This paper is intended to bridge the theoretical literature describing efficient intra-household behaviour and the development literature that collects empirical regularities pointing toward the existence of strategic decision-making among spouses.
It examines the key elements of the collective model and discusses its relevance to analysing intra-household behaviour in poor countries. It explores the role that risk and uncertainty, information asymmetries, power imbalances, arranged marriages, strategic investment, gender norms, and extended households play in the attainment of efficiency.

L’agent économique et ses représentations : une introductionBook chapterGilles Campagnolo, Jean-Sébastien Gharbi, Philippe Grill et Jean Magnan de Bornier, In: Revue de Philosophie Economique / Review of Economic Philosophy, 2018-11, Volume 19, Issue 1, pp. 3-13, Vrin, 2018
Qui travaille après 65 ans ?Journal articleAlain Trannoy, Insee Références, pp. 25-38, 2018

La part des personnes âgées de 65 à 74 ans qui sont en emploi est en forte croissance depuis 10 ans, même si elle ne représente encore que 5 %de cette classe d’âge. En comparaison avec les inactifs dumême âge, les actifs occupés entre 65 et 74 ans sont plus souvent des hommes, en bonne santé, plus diplômés et résidant dans l’agglomération parisienne. Les cadres salariés, mais aussi les indépendants et les agriculteurs sont surreprésentés dans ce groupe.
Comparés aux 60-64 ans en emploi, les actifs occupés entre 65 et 74 ans sont plus souvent indépendants et plus fréquemment à temps partiel quand ils sont salariés ; qu’ils soient salariés ou indépendants, leurs revenus d’activité sont plus faibles en moyenne.
Parmi les 65-74 ans en emploi, 70 %perçoivent également une pension de retraite ; ceux qui n’en perçoivent pas en parallèle sont plus souvent immigrés, de sexe féminin, en bonne santé et résidant dans l’agglomération parisienne. L’emploi de ces non-cumulants se distingue principalement par une durée de travail plus importante : 78 % sont à temps complet (contre 32 % pour ceux qui perçoivent une pension de retraite). Quatre profils types de personnes en emploi après 65 ans se dégagent : les employées peu diplômées à temps partiel, les très diplômés et très qualifiés urbains, les commerçants et enfin les agriculteurs âgés.
Enfin, parmi les déterminants extra-financiers qui sont associés à la décision de rester en emploi au-delà de 65 ans pour ceux qui étaient encore en emploi à cet âge, le non-salariat, l’absence de limitation dans les activités habituelles, la poursuite de l’activité du conjoint ou encore la faible différence d’âge avec le conjoint se détachent comme les facteurs explicatifs les plus significatifs.

Revue de philosophie économique : L’agent économique et ses représentations : une introductionBookGilles Campagnolo, Jean-Sébastien Gharbi, Philippe Grill et Jean Magnan de Bornier (Eds.), 2018-11, Volume 19(1), 206 pages, Vrin, 2018

Le 3 e Colloque international Philosophie économique a été organisé les 15 et 16 juin 2016 à Aix-en-Provence par le Greqam/Amse. Il a réuni des conférenciers venus de vingt-quatre pays, avec pour orateurs pléniers Cristina Bicchieri, John Davis et Daniel Hausman autour du thème de « l’agent économique et ses représentations ». Nous avons rassemblé dans le présent numéro spécial une sélection de textes présentés et discutés à cette occasion.
La manière dont on peut représenter « l’agent économique » importe à la fois du point de vue de la philosophie économique qui l’interroge, de la théorie économique qui l’utilise, et des travaux empiriques qui s’appuient sur les modèles qu’elle propose et, parfois, impose. Elle importe encore afin de comprendre la façon dont les institutions émergent, dont les sociétés s’organisent et dont divers mécanismes contribuent au « bien-être général » – que ceux-ci apparaissent spontanément ou qu’ils soient le résultat d’une création volontaire et pragmatique. Elle importe enfin également pour envisager (et possiblement) corriger des situations dans lesquelles les marchés sont incomplets ou n’existent tout simplement pas.
La question de l’agence (ou de l’« agentivité ») se pose en économie d’une manière dont la spécificité mérite discussion – prolongeant ainsi les travaux sur cette question. Malgré la diversité des termes rencontrés, en anglais comme en français (le colloque s’étant tenu dans les deux langues), pour désigner cet élément-clé des analyses proposées par les diverses sciences sociales, il semble que les économistes lui prêtent un intérêt qui ne se retrouve pas autant dans les autres disciplines…

Investigating the twin-deficit phenomenon among oil-exporting countries: Does oil really matter?Journal articleOlusegun Ayodele Akanbi et Rashid Sbia, Empirical Economics, Volume 55, Issue 3, pp. 1045-1064, 2018

This study empirically investigates the existence of twin deficits—the impact of fiscal policy on the current account—among selected major oil-exporting countries. Given the huge effects of the oil proceeds on these economies, the study separates the effects of oil on the fiscal balance from its effect on the current account balance. The investigation took a further step by grouping these countries—based on their fiscal policy actions over the period of years under review—into pro-cyclical and counter-cyclical fiscal countries. In line with the existing literature, the impact of fiscal balance on the current account balance takes into consideration the contemporaneous effects brought about by exchange rate fluctuations, the growth in GDP, rate of openness and the growth in money supply. The models are estimated based on a panel of 31 oil-exporting countries over the period 1984–2013, using the two-stage least squares estimation techniques. The results from all countries estimations reveal the existence of twin-deficit in the total economy. In the non-oil economy, on the other hand, the evidence of twin-deficit disappears. This evidence is also reported in the counter-cyclical fiscal countries. Results from pro-cyclical fiscal countries indicated the total opposite, revealing the existence of twin-deficit in the non-oil economy, while this evidence does not occur in the total economy. The indisputable conclusion is that oil dominance continues to blur the existence of twin deficits among the oil-exporting countries.

The Creation and Evolution of the Donor Funded Market for Antimalarials and the Growing Role of Southern FirmsJournal articleFabienne Orsi, Sauman Singh et Luis Sagaon-Teyssier, Science, Technology and Society, Volume 23, Issue 3, pp. 349-370, 2018

Since the early 2000s, the question of access to medicines at affordable prices for Southern populations has appeared as one of the major challenges for the international governance of health. But what is at stake is the creation of market for medicines in the global South, particularly countries in the Sub-Saharan Africa. These markets are new in nature in the sense that they are driven by international organisations where Southern firms, especially from India, occupy an increasingly important position. However, the specificity of these markets and the way they are constituted have been little analysed. In this article, we suggest focusing the attention on the constitution of the market of antimalarial drugs and highlighting the role played by Southern firms in this market. Our study focuses on the public sector market of antimalarial drugs. We provide an institutional and quantitative analysis of the creation of this public market. We then discuss the growing importance of the Southern firms, mainly Indian and Chinese, in this market.