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Introduced by Samuelson (1975), the Serendipity Theorem states that the competitive economy will converge towards the optimum steady-state provided the optimum population growth rate is imposed. This paper aims at exploring whether the Serendipity Theorem still holds in an economy with risky lifetime. We show that, under general conditions, including a perfect annuity market with actuarially fair return, imposing the optimum fertility rate and the optimum survival rate leads the competitive economy to the optimum steady-state. That Extended Serendipity Theorem is also shown to hold in economies where old adults work some fraction of the old-age, whatever the retirement age is fixed or chosen by the agents., Introduit par Samuelson (1975), le Serendipity Theorem énonce qu'une économie concurrentielle convergera vers son état stationnaire optimal à condition que le taux de natalité optimal soit imposé. Ce papier a pour but d'explorer si le Serendipity Theorem demeure valide dans une économie où la longueur de vie est sujette au risque. Nous montrons que, sous des conditions générales, incluant un marché d'annuités parfait offrant des rendements actuariellement justes, imposer le taux de natalité optimal et le taux de survie optimal mène l'économie concurrentielle à l'état stationnaire optimal. Il est démontré que ce Serendipity Theorem étendu reste valide lorsque les agents seniors travaillent une certaine fraction de leur temps, que l'âge de départ à la retraite soit fixé ou choisi par les agents eux-mêmes.

International audience; Between December 2007 and June 2008, the Court of Justice of the European Community (CJEC) pronounced four judgments (Viking, Laval, Rüffert and Luxembourg) which overtly question some of the specific features of European social models, regarding the right to strike, the nature of collectively-agreed provisions, as well as procedures for setting the minimum wage. This article begins by describing the circumstances in which those judgments were pronounced and then analyses the legal arguments giving priority to norms regarding the free provision of services over norms protecting workers. Secondly, it looks into the possible impact of such an approach of Community law, in terms both of weakening collectively-agreed provisions (based on the case of Sweden) and of implementing increasingly aggressive international subcontracting strategies, which call for new forms of collective mobilization (as the disputes that took place in the UK in 2009 show). European workers are expecting a quick response at European level, including a new directive on posted workers, while the institutions concerned remain, in contrast, very inert.; Entre décembre 2007 et juin 2008, la Cour de justice des communautés européennes rend quatre arrêts (Viking, Laval, Rüffert et Luxembourg) qui mettent en cause directement certaines spécificités des modèles sociaux européens, touchant au droit de grève, à la nature des dispositifs conventionnels et aux modalités de fixation des minima salariaux. La première partie de l’article campe les circonstances de ces arrêts et en analyse l’argumentaire juridique qui consacre la primauté des normes de libre prestation de services sur celles de protection des salariés. La seconde partie envisage les effets d’une telle orientation du droit communautaire, en termes de fragilisation des dispositifs conventionnels (le cas suédois sert de point d’appui à l’analyse) et de déploiement de stratégies de plus en plus agressives de recours à la sous-traitance internationale appelant de nouvelles formes de mobilisation collective (les conflits observés au Royaume-Uni au cours de l’année 2009 en témoignent). L’urgence des réponses attendues par les salariés au plan européen contraste singulièrement avec l’inertie des institutions qui pourraient en être porteuses.

This article analyzes the link between climate change and international migration. We use a two-country overlapping generations model with endogenous climate change, in which the production in the North generates climate change which negatively affects the productivity of the South. Our main findings are: (i) climate change will increase migration; (ii) small impacts of climate change have significant impacts on the number of migrants; (iv) a laxer immigration policy increases long- run migration, reduces climate change, increases North-South inequality if DRTS are significant; (v) a greener technology reduces long-run migration, provides a double- dividend in favor of the environment, reduces inequality if the migrants' impact to overall climate change is large. The preference over the policies thus depends on whether the policy maker targets inequality, wealth, the number of migrants or the environment, but the qualitative ranking between the policies does not change if the policies are costly.

This paper analyzes empirically a public policy promoting industrial clusters in France. Cluster policies have become popular in many countries but have not been extensively evaluated. We propose in this paper the first quantitative evaluation of a cluster policy exploiting firm-level data. We use data on production and employment for firms that benefited from the policy and on firms that did not, both before and after the policy started. We first show that the policy selected firms in sectors and regions in relative decline. Second, the policy did not succeed in reversing the relative decline in productivity for the targeted firms. The policy had no robust effect on employment or exports.

This paper develops a theory of optimal fertility behavior under mortality shocks. In an OLG model, young adults determine their optimal fertility, labor supply and life-cycle consumption with both exogenous child and adult mortality risks. We show that a rise in adult mortality exerts an ambiguous effect on both net and total fertility in a general equilibrium framework, while child mortality shocks unambiguously lead to a rise in total fertility, leaving net fertility unchanged. We complement our theory with an empirical analysis using a sample of 39 Sub-Saharan (SSA) countries over the 1980-2004 period, examining the overall effects of the child and adult mortality channels on both total and net fertility. We find child mortality to exert a robust, positive impact on total fertility but no impact on net fertility, whereas a rise in adult mortality is found to negatively influence both total and net fertility, whereas a rise in adult mortality is found to negatively influence both total and net fertility. Given the particular demographic profile of the HIV/AIDS epidemic (killing essentially young, active adults), we then conclude in favor of an ambiguous negative effect of the HIV/AIDS epidemic on net fertility in SSA.

This paper analyzes empirically the effect of spatial agglomeration of activities on the productivity of firms using French individual firm data from 1996 to 2004. This allows us to control for endogeneity biases that the estimation of agglomeration economies typically encounters. French firms benefit from localization economies, but not from urbanization economies nor from competition effects. The benefits generated by increased sectoral clustering, though positive and highly significant are modest and geographically very limited. The gains from clusters are also quite well internalized by firms in their location choice: we find very little difference between the geography that would maximize productivity gains and the geography actually observed.

Les recommandations de l’Union européenne sur les retraites se sont multipliées au cours des dernières années. Chronologiquement, la question de la réforme des systèmes de retraite est d’abord apparue à travers les textes et recommandations des acteurs en charge des questions de politique économique : Direction générale affaires économiques et financières de la Commission (DG ECFIN), Conseil Ecofin, Comité de politique économique (CPE), Banque centrale européenne. Avec la surveillance accrue des finances publiques (déficit, dette, dépenses publiques) dans le cadre du pacte de stabilité et de croissance et des grandes orientations de politique économique (Gope), les États sont toujours davantage exhortés à réformer leur système de retraite. Dans le jargon des textes communautaires, réformer signifie limiter les dépenses futures des retraites par répartition en réduisant le niveau relatif des pensions, en retardant l’âge de départ en retraite et en développant les dispositifs fondés sur la capitalisation (...).

An outline of the evolution from the birth up to present days of the macroeconomics is laid out, its emergence during the thirties, then the period of the domination of the Keynesian macroeconomics of the years 1950 to 1970. The following stage of the evolution has been the attack from Milton Friedman and Robert Lucas against Keynesian macroeconomics. We consider the works of these authors deserve the label of a "scientific revolution à la Kuhn", with the emergence of the dynamic and stochastic macroeconomics. Associated with this, the focus of macroeconomics has shifted. Themes linked to market failures, and especially to unemployment disappear, in favour of cycle and growth analysis, these last being studied from the postulate of efficient working of the system. These last years have seen the emergence of a "New Neoclassical Synthesis" mimicking the old synthesis in combining keynesian and classical elements, while adopting the new methodology of equilibrium discipline and of agents rational behaviour., Nous retraçons à grands traits l'évolution de la macroéconomie de sa naissance à nos jours, son émergence dans les années 1930, puis la période de règne sans partage de la macroéconomie keynésienne des années 1950 à 1970. L'étape suivante de son évolution est l'offensive menée par Milton Friedman et Robert Lucas contre la macroéconomie keynésienne. Les travaux de ces auteurs ont débouché sur un changement de perspective qui nous paraît mériter d'être épinglé comme une "révolution scientifique" à la Kuhn, l'émergence de la macroéconomie dynamique et stochastique. Avec celle-ci, le centre d'intérêt de la théorie et de la modélisation macroéconomie se déplace. Le thème des défaillances de l'économie de marché, et en particulier du chômage, est délaissé au profit d'un examen des phénomènes du cycle et de la croissance, ceux-ci étant étudiés à partir de l'hypothèse d'un fonctionnement efficace du système. Ces dernières années ont vu l'émergence d'une "nouvelle synthèse néoclassique" rejouant le jeu de la synthèse ancienne avec une combinaison d'éléments keynésiens et classiques, tout en adoptant la méthodologie nouvelle de discipline de l'équilibre et de rationalité des agents.

In this paper we propose a unifying approach to the study of recursive economic problems. Postulating an aggregator function as the fundamental expression of tastes, we explore conditions under which a utility function can be constructed. We also modify the usual dynamic programming arguments to include this class of models. We show that Bellman's equation still holds, so many results known for the additively separable case can be generalized for this general description of preferences. Our approach is general, allowing for both bounded and unbounded (above/below) returns. Many recursive economic models, including the standard examples studied in the literature, are particular cases of our setting.

We provide sufficient conditions on the objective functional and the constraint functions under which the Lagrangean can be represented by l(1) sequence of multipliers in infinite horizon discrete time optimal growth models. (C) 2003 Elsevier B.V. All rights reserved.

International audience; Wr prove existence of a competitive equilibrium in a version of a Ramsey (one sector) model in which agents are heterogeneous and gross investment is constrained to be non negative. We do so by converting the infinite-dimensional fixed point problem tated in terms of prices and commodities into a finite-dimensional Negishi problem involving individual weights in a social value function. This method allows us to obtain detailed results concerning the properties of competitive eqilibria. Because of the simplicity of techniques utilized our approach is amenable to be adapted by practioners in analogous problems often studied in macroeconomics

International audience

International audience; We incorporate a production technology that exhibits increasing returns to scale for small values of the capital stock and diminishing returns for the higher stocks at the firm level in a discrete-time version of Romer's endogenous growth model. We study the social planner's problem where the social production technology exhibits globally increasing returns to scale. The properties of the optimal paths are charaxterized. It is proved that for a given quality of knowledge technology, the countries can take off if their initial stock of capital is above a critical value. We nalyze the effect of three factors on the critical value: initial knowledge, quality of knowledge technology, and level of fixed costs associated with production.

International audience

International audience

This paper provides new developments in job search theory, incorporating a duality in search strategies which compose the offer rate. Two strategies are modelled. A first one, called passive strategy, consists in searching exclusively in the spatial area of the public employment agency. The alternative strategy allows to extend search area, using other media, like networks or advertisements. Introducing this duality leads us to ambiguous effects of search strategies on the theoretical exit rate. A micro-econometric estimation allows us to overcome this difficulty. A two-step method is chosen in order to, first, study the strategies' selection rule and, second, to take into account multiple destinations after unemployment and possible unobserved heterogeneity in the duration model. Results highlight the selectivity of the search strategies' choice, in particular the role of spatial constraints. Besides, they conclude to discriminate impacts of job search strategies on exit rates, according to the job found., Dans cet article, deux stratégies de recherche d'emploi concurrentes sont introduites comme facteurs explicatifs du taux de sortie du chômage. Le modèle de prospection en équilibre partiel construit oppose une première stratégie consistant à limiter la zone de recherche à la zone de compétence de l'agence publique pour l'emploi à une stratégie alternative, plus coûteuse, qui permet, à travers la mobilisation des procédures marchandes et du réseau social, d'élargir l'horizon spatial de la recherche. L'introduction de cette dualité des stratégies de recherche dans le cadre d'un modèle de recherche à environnement stationnaire fait apparaître à l'équilibre des effets théoriques ambigus sur la durée d'accès à l'emploi. L'estimation économétrique de la fonction de vraisemblance associée à l'expression du taux de sortie du chômage vise à lever cette ambiguité. Réalisée en deux étapes afin de contrôler la sélectivité du choix des stratégies de prospection, notamment l'effet des contraintes spatiales, l'estimation économétrique des taux de sortie du chômage contrôle également l'hétérogénéité des transitions individuelles vers l'emploi et la présence potentielle d'hétérogénéité inobservable. Les résultats économétriques concluent alors à l'endogénéité des stratégies de prospection et à leur influence discriminante sur les durées d'accès aux différents types emplois.