Optimal pension funding with demographic instability and endogenous returns on investment

This paper tries to explore some optimal funding policies for pension systems in a general equilibrium setting where funding affects returns on investment and wages through its impact on capital formation. This is done in the context of irregular demographic evolutions such as those expected in developed countries for the next century. Particular attention is given to the intergenerational welfare criterion which is used for designing optimal policies. It appears that funding receives low justification with a welfare criterion which assumes a high substitutability between consumptions of successive cohorts, implying a low concern for intergenerational equity. Funding is highly justified in the opposite case where a high level of consumption for some cohorts is not considered as a compensation for low consumption by others. However the optimal patterns of transfers and savings which are found in this latter case are not straightforward. Some simpler funding rules are explored in the last section of this paper, which show that non-optimal funding may imply, on the contrary, a high level of inequality between subsequent generations.Paper presented at the ISPE-conference Fiscal implications of an ageing population, May–June 1990 at Vaalsbroek, The Netherlands. We thank Pierre Pestieau for his remarks on a first draft of this paper. We also thank for their comments our two discussants Carol Propper and Lans Bovenberg, as well as other participants to the ISPE Conference. Any errors are, of course, ours.     

The use of traditional and modern methods of fertility control in Kinshasa, Zaire

Abstract The practice of post-partum abstinence has been a long-standing tradition in many societies of tropical Africa, yet recent research suggests an erosion of the taboo on post-partum sexual relations as a means of fertility control. The current study among women in the lower income groups in Kinshasa, Zaire, provides evidence of this. There is strong motivation toward child-spacing, as shown by 80 per cent of the women who reported to be currently practising some means of fertility control: 73 per cent with traditional methods, only 7 per cent with modern contraceptives. There appears to be some carry-over of traditional practice, in that abstinence is related to the age and nursing status of the last born child. However, the most widely practised method is withdrawal. This suggests a desire on the part of this population for alternatives to abstinence, an issue with important implications for future family planning programs in Zaire.     

Introduction. Ce que les écrits font au travail

As is known, large numbers of writings circulate within every kind of professional environment. As a result, there is extensive research on the formats, uses and roles of writings in work. However, the approach taken here is not to describe what is done with writings in work. The central hypothesis rests on a performative vision of writings, one that gives them the power to act, agency. It can be summed up as follows: what do writings “do” to work? Studying work through its writings is a way to connect two dimensions that are too often kept separate: situated activities on the one hand, organizational functions on the other. Indeed, writings are material and robust — though not always lasting — traces of concrete activities, and they provide a handhold for the rigorous analysis of work as close as possible to its conditions of realization. However, writings travel and circulate. They form links between workers, groups, workshops, services, firms, without which production could not take place. They stretch work beyond its source. To track them is therefore to shift the field of enquiry to moments other than the present of the observed situation, and also to other nearby, surrounding workspaces. This brings out the procedural and interactive dimensions of organizations, their integrating capacity. Exploring what writings do to work is therefore not only to place oneself at an intermediate level between situated action and organized action. For the sociologist, it is a way of connecting these two perspectives “on paper”, by embedding the analysis of the actual work in spatially and temporally broader collective actions, and by documenting organizational analysis on the basis of observed work situations. It is a way of contributing to a more extensive ecology of activity, more clearly anchored within its organizational envelope.     

Correlation and variable importance in random forests

This paper is about variable selection with the random forests algorithm in presence of correlated predictors. In high-dimensional regression or classification frameworks, variable selection is a difficult task, that becomes even more challenging in the presence of highly correlated predictors. Firstly we provide a theoretical study of the permutation importance measure for an additive regression model. This allows us to describe how the correlation between predictors impacts the permutation importance. Our results motivate the use of the recursive feature elimination (RFE) algorithm for variable selection in this context. This algorithm recursively eliminates the variables using permutation importance measure as a ranking criterion. Next various simulation experiments illustrate the efficiency of the RFE algorithm for selecting a small number of variables together with a good prediction error. Finally, this selection algorithm is tested on the Landsat Satellite data from the UCI Machine Learning Repository.     

Trends in Mortality Decrease and Economic Growth

The vast literature on extrapolative stochastic mortality models focuses mainly on the extrapolation of past mortality trends and summarizes the trends by one or more latent factors. However, the interpretation of these trends is typically not very clear. On the other hand, explanation methods are trying to link mortality dynamics with observable factors. This serves as an intermediate step between the two methods. We perform a comprehensive analysis on the relationship between the latent trend in mortality dynamics and the trend in economic growth represented by gross domestic product (GDP). Subsequently, the Lee-Carter framework is extended through the introduction of GDP as an additional factor next to the latent factor, which provides a better fit and better interpretable forecasts.     

联合国改革努力的历史发展

联合国改革长期以来是国际社会关注的焦点,为了理解这一进程的未来走向,有必要清醒地认识它所经历的历史发展.联合国改革涉及组织结构、管理程序以及宪制安排三个方面,涵盖国际安全以及经济和社会问题两个主要领域,反映出各国在这些问题上的不同立场和观点.联合国改革努力的不同规划表明,在这些领域取得实质性突破仍然困难重重.     

Postmining Management in France: Situation and Perspectives

Even if most French mines are definitively closed, potential risks remain above the abandoned sites. In addition to surface instability, some mining sites may be affected by dangerous gas emissions, flooding events, or environmental impacts. Those kinds of disorders strongly influence the land-use management of the concerned areas. The present article presents the French mining historical context and identifies the major kinds of residual risks and harmful effects that may affect abandoned mine sites. The prevention policy applied on the national territory is then discussed and prospects for further developments are proposed.     

Representation,Propagation, and Decision Issues in Risk Analysis Under Incomplete Probabilistic Information

This article tries to clarify the potential role to be played by uncertainty theories such as imprecise probabilities, random sets, and possibility theory in the risk analysis process. Instead of opposing an objective bounding analysis, where only statistically founded probability distributions are taken into account, to the full‐fledged probabilistic approach, exploiting expert subjective judgment, we advocate the idea that both analyses are useful and should be articulated with one another. Moreover, the idea that risk analysis under incomplete information is purely objective is misconceived. The use of uncertainty theories cannot be reduced to a choice between probability distributions and intervals. Indeed, they offer representation tools that are more expressive than each of the latter approaches and can capture expert judgments while being faithful to their limited precision. Consequences of this thesis are examined for uncertainty elicitation, propagation, and at the decision‐making step.