Although volunteering is considered a good strategy for successful ageing, not many older adults are engaged in voluntary work and those who are do so mainly sporadically. This study focuses on time invested in volunteering rather than on doing voluntary work or not, as is often done in studies so far. By combining the theory of resources for volunteering with a functional and structural approach to volunteering, this cross-sectional study seeks to shed light on a wide range of factors associated with the intensity of volunteering. The study is based on a sample of 1,599 volunteers aged 50 and older participating in the Norwegian study on Life Course, Ageing and Generation Study (NorLAG). The survey includes, among others, detailed information about demographics and time invested in voluntary work and questions about attitudes, motivations, structural and other potential barriers to volunteering. Multivariate linear regression analyses indicate that a religious attitude is associated with elevated hours spent on voluntary work, while co-habitation is associated with a decreased engagement in voluntary work. In addition, people who are motivated to volunteer because they find it interesting and because volunteering allows them to use their competence spend more time volunteering. Human capital, i.e. education, income and subjective health, are not associated with the number of hours invested in voluntary work. The likelihood of contributing more volunteering hours of older men is 17.5 per cent higher than that of older women. We found no indication of a relation between work status, functional limitations, urbanisation or ethnicity and voluntary work engagement. Policies aiming to increase time investment of volunteers should strive for an optimal fit between the nature of the voluntary work and the interests and skills of the volunteers. In designing interventions to stimulate higher engagement in voluntary work, one should further promote strategies for flexible time commitment.

In the classical risk model with initial capital u, let τ(u) be the time of ruin, X+(u) be the risk reserve just before ruin, and Y+(u) be the deficit at ruin. Gerber and Shiu (1998) defined the function mδ(u) =E[e−δ τ(u)w(X+(u), Y+(u)) 1 (τ(u) < ∞)], where δ ≥ 0 can be interpreted as a force of interest and w(r,s) as a penalty function, meaning that mδ(u) is the expected discounted penalty payable at ruin. This function is known to satisfy a defective renewal equation, but easy explicit formulae for mδ(u) are only available for certain special cases for the claim size distribution. Approximations thus arise by approximating the desired mδ(u) by that associated with one of these special cases. In this paper a functional approach is taken, giving rise to first-order correction terms for the above approximations.

Les macroinvertébrés benthiques sont couramment utilisés dans le domaine de la bioindication. Pourtant les méthodes indicielles globales ne permettent pas de poser un diagnostic sur les causes réelles de dégradation. Cette étude propose donc d'intégrer les avancées théoriques récentes mettant en relation les stratégies biologiques des organismes (reproduction, durée de vie, habitudes alimentaires et respiratoires) avec les perturbations de leur environnement. Cette approche a été appliquée à la Chalaronne, un cours d'eau soumis à des effluents d'une station d'épuration. L'analyse biocénotique, basée sur l'abondance des taxons, permet de séparer les stations amont des stations aval puisque 17,9 % de la variabilité totale du tableau de données y est consacrée. Au niveau fonctionnel, l'utilisation des traits biologiques définis pour chaque taxon permet une meilleure séparation amont - aval, puisque la valeur obtenue est de 23,1 %. Cet exemple nous montre que la structure fonctionnelle observée en amont correspond à des caractéristiques de résilience. Au contraire la structure fonctionnelle observée en aval correspond à des caractéristiques de résistance. L'approche fonctionnelle présente donc deux intérêts : d'une part elle permet une bonne discrimination des situations étudiées, d'autre part elle ouvre des perspectives intéressantes pour l'étude des fonctionnalités biologiques des écosystèmes.