Publications
The understanding of ecosystem services is essential to support sustainable use and preservation of ecosystems. Coralligenous habitats, main contributors of the Mediterranean marine biodiversity, are yet understudied in term of services provided. This study presents an original small-scale approach to investigate the services provided by coralligenous habitats of a French study area consisting of two marine sites (Marseille and Port-Cros sites) in order to cover two contrasted anthropogenic pressure despite the small-scale. Our results are based on the opinions of 43 experts who ranked 15 services in terms of existence and level of importance for human well-being: supporting ecological functions were considered the most important, then provisioning and cultural services. Regulating services were considered uncertain due to a lack of knowledge. The small-scale approach highlighted a need for a referential frame to determine the existence of services (e.g. geographical and temporal scales, benefits and beneficiaries levels).
BACKGROUND:
In 2016, countries agreed on a Fast-Track strategy to "end the AIDS epidemic by 2030". The treatment and prevention components of the Fast-Track strategy aim to markedly reduce new HIV infections, AIDS-related deaths and HIV-related discrimination. This study assesses the economic returns of this ambitious strategy.
METHODS:
We estimated the incremental costs, benefits and economic returns of the Fast-Track scenario in low- and middle-income countries, compared to a counterfactual defined as maintaining coverage of HIV-related services at 2015 levels. The benefits are calculated using the full-income approach, which values both the changes in income and in mortality, and the productivity approach.
FINDINGS:
The incremental costs of the Fast-Track scenario over the constant scenario for 2017-2030 represent US$86 billion or US$13.69 per capita. The full-income valuation of the incremental benefits of the decrease in mortality amounts to US$88.14 per capita, representing 6.44 times the resources invested for all countries. These returns on investment vary by region, with the largest return in the Asia-Pacific region, followed by Eastern and Southern Africa. Returns using the productivity approach are smaller but ranked similarly across regions.
INTERPRETATION:
In all regions, the economic and social value of the additional life-years saved by the Fast-Track approach exceeds its incremental costs, implying that this strategy for ending the AIDS epidemic is a sound economic investment.
The aim of this paper is to study the interplay between long term productive investments and more short term and liquid speculative ones. A three-period lived overlapping generations model allows us to make this distinction. Agents have a portfolio decision. When young, they can invest in human capital that is a productive long term investment that provides a return during the following two periods. When young or in the middle age, they can invest in a bubble. Young individuals can also borrow on a credit market to finance the productive investment. However, the amount borrowed is limited by a credit constraint. We show that the existence of a stationary bubble raises productive investment and production when the bubleless economy is credit constrained and dynamically efficient. Indeed, young agents sell short the bubble to increase productive investments, whereas traders at middle age transfer wealth to old age. The bubble allows to relax the credit constraint. We outline that a permanent technological shock inducing either a larger return of capital in the short term or a similar increase in the return of capital in both periods raises productive capital, production and the bubble size. We use our framework to discuss the effect on the occurrence of bubbles of financial regulation and fiscal policy.
On many two-sided platforms, users on one side not only care about user participation and usage levels on the other side, but they also care about participation and usage of fellow users on the same side. Most prominent is the degree of seller competition on a platform catering to buyers and sellers. In this paper, we address how seller competition affects platform pricing, product variety, and the number of platforms that carry trade.
We review the most recent advances in distributed optimal control applied to Environmental Economics, covering in particular problems where the state dynamics are governed by partial differential equations (PDEs). This is a quite fresh application area of distributed optimal control, which has already suggested several new mathematical research lines due to the specificities of the Environmental Economics problems involved. We enhance the latter through a survey of the variety of themes and associated mathematical structures beared by this literature. We also provide a quick tour of the existing tools in the theory of distributed optimal control that have been applied so far in Environmental Economics.
We solve a linear-quadratic model of a spatio-temporal economy using a polluting one-input technology. Space is continuous and heterogenous: locations differ in productivity, nature self-cleaning technology and environmental awareness. The unique link between locations is transboundary pollution which is modelled as a PDE diffusion equation. The spatio-temporal functional is quadratic in local consumption and linear in pollution. Using a dynamic programming method adapted to our infinite dimensional setting, we solve the associated optimal control problem in closed-form and identify the asymptotic (optimal) spatial distribution of pollution. We show that optimal emissions will decrease at given location if and only if local productivity is larger than a threshold which depends both on the local pollution absorption capacity and environmental awareness. Furthermore, we numerically explore the relationship between the spatial optimal distributions of production and (asymptotic) pollution in order to uncover possible (geographic) environmental Kuznets curve cases.
Utiliser le revenu pour mesurer les conditions de vie des enfants est de plus en plus critiqué, en particulier pour les très jeunes enfants. Cet article propose une description multidimensionnelle de la pauvreté des enfants en France, au moment de leur naissance et pendant leur première année de vie, en utilisant une mesure de la pauvreté monétaire et une approche de la pauvreté en conditions de vie, à partir de l’Étude longitudinale française depuis l’enfance (la cohorte Elfe) qui est une enquête nationale représentative portant sur plus de dix-huit mille enfants nés en France en 2011. Les résultats montrent que la pauvreté monétaire ne coïncide pas toujours avec la pauvreté en conditions de vie : certains enfants vivent dans des ménages à faibles revenus sans pour autant être considérés comme pauvres tandis que d’autres dont les revenus sont plus élevés peuvent néanmoins être considérés comme pauvres au regard des conditions de vie. Cette approche permet d’être plus précis et plus nuancé dans la compréhension de la pauvreté des enfants à de très jeunes âges.
