Ground beetle (Coleoptera: Carabidae) communities on green roofs in Switzerland: synthesis and perspectives

Urban Ecosystems - Green roofs have recently gained recognition for their potential contribution to urban ecosystems by providing, among other services, habitat for plants and animals, and stepping...     

Reduced costs propagation in an efficient implicit enumeration for the 01 multidimensional knapsack problem

In a previous work we proposed a variable fixing heuristics for the 0-1 Multidimensional knapsack problem (01MDK). This approach uses fractional optima calculated in hyperplanes which contain the binary optimum. This algorithm obtained best lower bounds on the OR-Library benchmarks. Although it is very attractive in terms of results, this method does not prove the optimality of the solutions found and may fix variables to a non-optimal value. In this paper, we propose an implicit enumeration based on a reduced costs analysis which tends to fix non-basic variables to their exact values. The combination of two specific constraint propagations based on reduced costs and an efficient enumeration framework enable us to fix variables on the one hand and to prune significantly the search tree on the other hand. Experimentally, our work provides two main contributions: (1) we obtain several new optimal solutions on hard instances of the OR-Library and (2) we reduce the bounds of the number of items at the optimum on several harder instances.     

Wage and Productivity Differentials in Japan: The Role of Labor Market Mechanisms

This paper aims at explaining two stylized facts of the Lost Decade in Japan: rising wage inequalities and increasing firm‐level productivity differentials. We build a model where firms can choose between efficiency wages with endogenous effort and competitive wages, and show that it can replicate those facts. Using Japanese microeconomic data, we find support for the existence of efficiency wages in one group of firms and competitive wages in the other group. Based on those results, a simulation shows that the share of firms using efficiency wages has declined, within sectors, during the Lost Decade, as predicted by the model.     

The Impact of Growth,Labour Cost and Working Time on Employment: Lessons from the French Experience

Abstract. In order to account for the evolution of employment at the macro‐economic level, we have developed a model wherein employment is explained by added value, working time and real labour cost. Estimations using quarterly French macro‐economic data are carried out in a multivariate framework for three sets of sectors. We obtain a relationship in which employment rises when there is growth and falls when labour cost or working time rises, in both industrial and non‐industrial sectors. This model then allows retrospective measurement of the contributions of each of the variables with respect to employment inflections since the mid‐1980s.     

The relationship between organisational change and being a perpetrator of workplace bullying: A three-wave longitudinal study

ABSTRACT

While research has unravelled the association between organisational change and being a target of workplace bullying, scholars have still to shed light on the perpetrator perspective of this association. In the current study, we further the literature by investigating the relationship between exposure to organisational change and being a perpetrator of workplace bullying. We introduced perceptions of psychological contract breach as a mechanism that accounts for the process in which exposure to organisational change leads employees to direct bullying behaviours to other members of the organisation. Using three-wave longitudinal data from 1994 employees we estimated a between-subjects mediation model controlling for autoregressive effects. Results confirmed our hypothesis that exposure to organisational change at Time 1 was positively related to being a perpetrator of workplace bullying at Time 3 through perceptions of psychological contract breach at Time 2. These findings suggest that organisations should invest in factors that lower employees’ likelihood to perceive psychological contract breach in the aftermath of organisational change because these perceptions may indeed result in the enactment of workplace bullying towards other members of the organisation.     

Confidence Intervals for Conditional Tail Risk Measures in ARMA–GARCH Models

ABSTRACT

ARMA–GARCH models are widely used to model the conditional mean and conditional variance dynamics of returns on risky assets. Empirical results suggest heavy-tailed innovations with positive extreme value index for these models. Hence, one may use extreme value theory to estimate extreme quantiles of residuals. Using weak convergence of the weighted sequential tail empirical process of the residuals, we derive the limiting distribution of extreme conditional Value-at-Risk (CVaR) and conditional expected shortfall (CES) estimates for a wide range of extreme value index estimators. To construct confidence intervals, we propose to use self-normalization. This leads to improved coverage vis-à-vis the normal approximation, while delivering slightly wider confidence intervals. A data-driven choice of the number of upper order statistics in the estimation is suggested and shown to work well in simulations. An application to stock index returns documents the improvements of CVaR and CES forecasts.     

Organisation,Emergence and Cambridge Social Ontology

John Searle has mistakenly claimed that emergence is the central concept in the account of social ontology defended by Tony Lawson, the central figure in the project now regularly referred to as Cambridge Social Ontology. This is not the case. Rather, if any concept can be considered central for Lawson, it is organisation. In this paper, I explain how Searle could misunderstand Lawson and, in doing so, I bring out the importance of organisation for understanding how phenomena, both social and non-social, are constituted.     

The RSA (Revenu de solidarité active) and back‐to‐work incentives in France

Using an inventory of local and/or non‐statutory transfers (droits connexes) in 13 French towns and cities, the article first measures the gains from returning to work for recipients of national, statutory means‐tested benefits (Revenu minimum d'insertion— RMI, and Allocation parent isolé— API) by type of household before 2009. The reforms of national, statutory benefits carried out during the 2000s, especially those affecting the working tax credit (Prime pour l'emploi— PPE), failed to ensure that the recipients of means‐tested benefits always stood to gain financially from returning to work. The effects of the reforms were offset by the effects of other measures. The article then simulates the effects of the introduction of the Revenu de solidarité active (RSA) in place of the RMI in 2009, and takes into account the way that local and/or non‐statutory transfers are modified by increases in national, statutory transfers. We observe that the RSA eliminates the financial disincentives to returning to work for almost all localities and types of household. The article shows that the marginal tax rate of 38 per cent chosen by the government is very close to the upper limit compatible with a back‐to‐work incentive.