Survival, reproduction and congestion: The spaceship problem re-examined

This paper re-examines the spaceship problem, i.e. the design of the optimal population under a fixed living space, by focusing on the dilemma between adding new beings and extending the life of existing beings. For that purpose, we characterize, under time-additive individual welfare depending negatively on population density, the preference ordering of a utilitarian social planner over lifetime-equal histories, i.e. histories with demographic conditions yielding an equal finite number of life-periods (imposed by resources constraints). The analysis of the spaceship problem contradicts widespread beliefs about the populationism of Classical Utilitarianism and the antipopulationism of Average Utilitarianism. We also study the invariance property exhibited by various utilitarian rankings to the total space available and to individual preferences. Finally, we compare histories for a spaceship with a stationary population, and try to accomodate intuitions about posterity and renewal of populations.environmental congestion ; fertility ; longevity ; population ethics ; utilitarianism ; renewal

Sustainability, resource substitution in energy inputs and learning

We assess the impact of the existence of a costly energy substitute (like wind, solar) for a non-renewable resource (like oil, coal) on the sustainability of consumption. The prospects for sustainability depend crucially on the costs of this substitute. If one can reduce the costs of the resource substitute via learning-by-using then we find that still this does not guarantee sustainability. Also, the poorer a country the less it will take the learning-by-using effect into account and the more likely it will be unsustainable.Renewable resource, non-renewable resource, substitution, sustainability, learningby- using.

Learning-by-doing and the Costs of a Backstop for Energy Transition and Sustainability

We assess the impact of being able to substitute an unlimited but costly energy substitute (like wind, solar) for a non-renewable resource (like oil, coal) in a model of sustainable growth. The prospects for sustainability on the optimal path depend crucially on the costs of this substitute.Furthermore, the poorer a country, measured in terms of capital stock at a given point in time, the later it should switch to the renewable substitute, and the more likely it will be unsustainable. Taking learning-by-doing in account, we find that this leads to an earlier switching time but does not guarantee sustainability.backstop technology; non-renewable resource; resource substitution; sustainability; learning-by-doing.

Longevity and environmental quality in an OLG model

Whereas existing OLG models with endogenous longevity neglect the impact of environmental quality on mortality, this paper studies the design of the optimal public intervention in a two-period OLG model where longevity is influenced positively by health expenditures, but negatively by pollution due to production. It is shown that if individuals, when choosing how much to spend on health, do not internalize the impact of their decision on environmental quality (i.e. the space available for each person), the decentralization of the social optimum requires a tax not only on capital income, but also, on health expenditures. The sensitivity of the optimal second-best public intervention is also explored numerically.longevity, health care, natural environment, pollution

Tradable pollution permits in dynamic general equilibrium: can optimality and acceptability be reconciled?

In this paper we study the optimal growth path and its decentralization in a two-sector overlapping- generations model with pollution. One sector (power generation) is polluting and the other (final good) is not. Pollution is regulated by tradable emission permits. The issue is whether the optimal growth path can be replicated in equilibrium with pollution permits, given that some permits must be issued free of charge for the sake of political acceptability. We provide a policy rule that allows optimality and acceptability to be reconciled.general equilibrium, optimal growth, pollution, tradable emission permits, acceptability

Bankable emission permits under uncertainty and optimal risk-management rules.

This article proposes a theory of banking of emission permits under conditions of regulatory uncertainty. Based on a two-period partial equilibrium framework, we examine the effects of increasing risk - in the sense of a mean-preserving spread - regarding a future permits allocation at the firm-level. We also examine the role of an agency to pool risks by re-allocating permits for a group of firms. Our results are twofold. First, an increase in risk may lead to changes in a firm’s banking strategy, depending on the third partial derivative of its production function with respect to pollution. Second, we define an optimal risk-sharing rule between agents to respond to political decision changes. Our results overall suggest that the bankability of permits may be used as a risk-management tool.Banking; Emission permits; Policy risk; Uncertainty;

Learning-by-doing and the Costs of a Backstop for Energy Transition and Sustainability

We assess the impact of being able to substitute an unlimited but costly energy substitute (like wind, solar) for a non-renewable resource (like oil, coal) in a model of sustainable growth. The prospects for sustainability on the optimal path depend crucially on the costs of this substitute.Furthermore, the poorer a country, measured in terms of capital stock at a given point in time, the later it should switch to the renewable substitute, and the more likely it will be unsustainable. Taking learning-by-doing in account, we find that this leads to an earlier switching time but does not guarantee sustainability

Sustainability, resource substitution in energy inputs and learning

We assess the impact of the existence of a costly energy substitute (like wind, solar) for a non-renewable resource (like oil, coal) on the sustainability of consumption. The prospects for sustainability depend crucially on the costs of this substitute. If one can reduce the costs of the resource substitute via learning-by-using then we find that still this does not guarantee sustainability. Also, the poorer a country the less it will take the learning-by-using effect into account and the more likely it will be unsustainable

Ressources renouvelables et quotas d’exploitation dans un modèle à générations imbriquées

Dans le cadre d'un modèle à générations imbriquées, nous supposons que la gestion d'une ressource renouvelable correspond à l'émission de quotas d'exploitation transférables. Chaque agent a la possibilité d'utiliser les quotas dans la production ou de les vendre à la génération suivante. Nous montrons qu'une telle politique de gestion d'une ressource naturelle renouvelable est possible seulement pour certains niveaux de ressource au moment de l'introduction des quotas. Nous montrons alors que les quotas conduisent à l'existence d'un unique équilibre stable de long terme fonction du niveau d'exploitation défini par le planificateur.Quotas d’exploitation, Ressources renouvelables, Générations imbriquées

Comportement des groupes d’investissement face à une incertitude sur l’environnement

Nous proposons d'étudier dans un modèle à deux secteurs de production, les effets d'une incertitude portant sur la qualité de l'environnement sur les comportements de choix de portefeuille et d'épargne des agents. Nous supposons que les individus investissent dans les firmes par l'intermédiaire de groupes d'investissement. Nous montrons, alors qu'à l'équilibre macroéconomique, un accroissement de risque peut conduire à une diminution du stock de capital et favoriser les firmes à effet certain sur l'environnement. Ces résultats dépendent des effets de la pollution sur la consommation et des comportements de précaution des individusEnvironnement, Risque, Choix de portefeuille, Epargne