Unconditional Quantile Treatment Effects Under Endogeneity

This article develops estimators for unconditional quantile treatment effects when the treatment selection is endogenous. We use an instrumental variable (IV) to solve for the endogeneity of the binary treatment variable. Identification is based on a monotonicity assumption in the treatment choice equation and is achieved without any functional form restriction. We propose a weighting estimator that is extremely simple to implement. This estimator is root n consistent, asymptotically normally distributed, and its variance attains the semiparametric efficiency bound. We also show that including covariates in the estimation is not only necessary for consistency when the IV is itself confounded but also for efficiency when the instrument is valid unconditionally. An application of the suggested methods to the effects of fertility on the family income distribution illustrates their usefulness. Supplementary materials for this article are available online.     

Le corps en jeu : les conditions sociales de l’arrêt de travail des footballeurs professionnels

Underlaid by a long-term case study in a professional football club, this analysis of the social conditions that led these players to temporarily stop work when their physical integrity was impaired focuses on relations within the work group. It describes how this process fits into the framework of social relations between various categories of workers who adjust individually and collectively to occupational requirements. While inquiring into the conditions of bringing players physically into play, it focuses on the practices of members of the medical staff whose position within the group is awkward.     

Business ethics,company value and ownership structure

This paper examines the effect of ethical performance on the value of a company and the attractiveness of its stocks for major owners; institutional investors and insiders. Using the Ethisphere^® Institute Ethics Quotient to distinguish between ethical and unethical companies, results show that good ethical performance enhanced company value for a sample of 240 large US companies. Furthermore, strong evidence is found that institutional investors are attracted to ethical companies, but that insiders do not show any investment preferences based on the ethical performance of a company.

     

Estimation of Conditional Ranks and Tests of Exogeneity in Nonparametric Nonseparable Models

Consider a nonparametric nonseparable regression model Y = ?(Z, U), where ?(Z, U) is strictly increasing in U and U ～ U[0, 1]. We suppose that there exists an instrument W that is independent of U. The observable random variables are Y, Z, and W, all one-dimensional. We construct test statistics for the hypothesis that Z is exogenous, that is, that U is independent of Z. The test statistics are based on the observation that Z is exogenous if and only if V = F_Y|Z(Y|Z) is independent of W, and hence they do not require the estimation of the function ?. The asymptotic properties of the proposed tests are proved, and a bootstrap approximation of the critical values of the tests is shown to be consistent and to work for finite samples via simulations. An empirical example using the U.K. Family Expenditure Survey is also given. As a byproduct of our results we obtain the asymptotic properties of a kernel estimator of the distribution of V, which equals U when Z is exogenous. We show that this estimator converges to the uniform distribution at faster rate than the parametric n^{? 1/2}-rate.     

From Linear to Semidefinite Programming: An Algorithm to Obtain Semidefinite Relaxations for Bivalent Quadratic Problems

In this paper, we present a simple algorithm to obtain mechanically SDP relaxations for any quadratic or linear program with bivalent variables, starting from an existing linear relaxation of the considered combinatorial problem. A significant advantage of our approach is that we obtain an improvement on the linear relaxation we start from. Moreover, we can take into account all the existing theoretical and practical experience accumulated in the linear approach. After presenting the rules to treat each type of constraint, we describe our algorithm, and then apply it to obtain semidefinite relaxations for three classical combinatorial problems: the K-CLUSTER problem, the Quadratic Assignment Problem, and the Constrained-Memory Allocation Problem. We show that we obtain better SDP relaxations than the previous ones, and we report computational experiments for the three problems.     

Sex and cultural differences in the acceptance of functional foods: a comparison of American, Canadian, and French college students

OBJECTIVE: Functional foods (FF)--foods containing nutritional supplements in addition to natural nutrients--have an increasing presence in the marketplace. Expanding on previous research, the authors investigated college students' acceptance of FF. PARTICIPANTS: In September--March 2004, 811 undergraduates in Canada, the United States, and France participated in the study. METHODS: A self-administered questionnaire measured students' general food attitudes and beliefs as well as FF-related knowledge, attitudes, beliefs, and purchase intention. RESULTS: Overall, participants slightly favored FF over traditional foods. However, although most respondents associated FF with positive health benefits, many remained dubious of currently available FF information. In terms of culture and sex, the authors found small but significant divergences in FF knowledge, attitudes, and behaviors. CONCLUSIONS: Stronger labeling and education efforts may increase cross-cultural acceptance of FF by college students.     

PERSONALITY,INFORMATION ACQUISITION,AND CHOICE UNDER UNCERTAINTY: AN EXPERIMENTAL STUDY

This article studies the role of personality in choice under risk and uncertainty. We explore the hypothesis that personality plays a role in decision making in situations of uncertainty but not in situations of risk. In addition to offering support for this main hypothesis, we explore the various pathways through which personality exerts its influence. What we find is that in uncertain environments, where decision makers are able to acquire information about the unknown probability distributions they face, personality variables influence the type of information people acquire, which then influences their choice. Our experimental design brings in two novel aspects of choice under uncertainty: information acquisition and advice. The findings indicate that indeed, under uncertainty, personality matters for choice in a way it does not under risk. Furthermore, the results suggest that personality can play a role at multiple levels, such as people's preferences for certain types of information and the likelihood of following advice. (JEL C90, D03, D81)     

Nest design in a changing world: Great tit <Emphasis Type="Italic">Parus major</Emphasis> nests from a Mediterranean city environment as a case study

Investigations of urbanization effects on birds have focused mainly on breeding traits expressed after the nest-building stage (e.g. first-egg date, clutch size, breeding success, and offspring characteristics). Urban studies largely ignored how and why the aspects of nest building might be associated with the degree of urbanization. As urban environments are expected to present novel environmental changes relative to rural environments, it is important to evaluate how nest-building behavior is impacted by vegetation modifications associated with urbanization. To examine nest design in a Mediterranean city environment, we allowed urban great tits (Parus major) to breed in nest boxes in areas that differed in local vegetation cover. We found that different measures of nest size or mass were not associated with vegetation cover. In particular, nests located adjacent to streets with lower vegetation cover were not smaller or lighter than nests in parks with higher vegetation cover. Nests adjacent to streets contained more pine needles than nests in parks. In addition, in nests adjacent to streets, nests from boxes attached to pine trees contained more pine needles than nests from boxes attached to other trees. We suggest that urban-related alterations in vegetation cover do not directly impose physical limits on nest size in species that are opportunistic in the selection of nesting material. However, nest composition as reflected in the use of pine needles was clearly affected by habitat type and the planted tree species present, which implies that rapid habitat change impacts nest composition. We do not exclude that urbanization might impact other aspects of nest building behaviour not covered in our study (e.g. costs of searching for nest material), and that the strengths of the associations between urbanization and nest structures might differ among study populations or species.     

A new universal resample-stable bootstrap-based stopping criterion for PLS component construction

We develop a new robust stopping criterion for partial least squares regression (PLSR) component construction, characterized by a high level of stability. This new criterion is universal since it is suitable both for PLSR and extensions to generalized linear regression (PLSGLR). The criterion is based on a non-parametric bootstrap technique and must be computed algorithmically. It allows the testing of each successive component at a preset significance level \(\alpha \). In order to assess its performance and robustness with respect to various noise levels, we perform dataset simulations in which there is a preset and known number of components. These simulations are carried out for datasets characterized both by \(n>p\), with n the number of subjects and p the number of covariates, as well as for \(n<p\). We then use t-tests to compare the predictive performance of our approach with other common criteria. The stability property is in particular tested through re-sampling processes on a real allelotyping dataset. An important additional conclusion is that this new criterion gives globally better predictive performances than existing ones in both the PLSR and PLSGLR (logistic and poisson) frameworks.     

How do immigrant parents of children with complex health needs manage to cope in their daily lives?

Daily life with children who have complex health needs can be stressful for parents. Immigrant parents are vulnerable to stress because they may lack language skills and knowledge about the health care system and have limited social networks. In this study, we focus on how immigrant parents of children with complex health needs use emotion‐focused and problem‐focused coping strategies to manage their daily life, and how their self‐efficacy and the immigration process may affect their coping. This qualitative study had an exploratory design with individual and focus group interviews. The sample comprised 27 parents—18 mothers and 9 fathers—from Pakistan, Poland, and Vietnam. The findings indicated that the parents' love for their child helps them to cope in their daily life. Newly arrived migrants, single mothers with a severely ill child who lacked support and migrant parents with language difficulties struggle to cope. Some of the stress is related to personal, social and structural problems, and to the insufficient resources available to meet the child's needs. The parents used both emotion‐focused and problem‐focused coping strategies. The parents noted that access to both universal and selective welfare services is an important factor that contributed to their self‐efficacy and coping.