Limit Theorems for Estimating the Parameters of Differentiated Product Demand Systems

We provide an asymptotic distribution theory for a class of Generalized Method of Moments estimators that arise in the study of differentiated product markets when the number of observations is associated with the number of products within a given market. We allow for three sources of error: the sampling error in estimating market shares, the simulation error in approximating the shares predicted by the model, and the underlying model error. The limiting distribution of the parameter estimator is normal provided the size of the consumer sample and the number of simulation draws grow at a large enough rate relative to the number of products. We specialise our distribution theory to the Berry, Levinsohn, and Pakes (1995) random coefficient logit model and a pure characteristic model. The required rates differ for these two frequently used demand models. A small Monte Carlo study shows that the difference in asymptotic properties of the two models are reflected in the models' small sample properties. These differences impact directly on the computational burden of the two models.Choice models, Method of moments, Random coefficients, Product differentiation

Psychological interventions for patients with chronic back pain

Chronic back pain is a major cause of disability and absenteeism in Western countries. Intense suffering associated with backache is pooly relieved by traditional medical treatments and many alternative therapies have been developed to approach this problem, including recent advances in psychological interventions. In this regard, we discuss here: 1) five common techiniques of the cognitive-behavioural approach (relaxation, operant, cognitive, social training and coping); 2) the operant activities training programme; 3) a clinical case ilustrating the application of this programme.Lombalgia crônica é uma causa importante de incapacidade física e ausência do trabalho nos países ocidentais. O desconforto intenso associado a este sintoma não é satisfatoriamente aliviado pela terapêutica médica tradicional, levando ao desenvolvimento de terapias alternativas, incluindo avanços recentes nas intervenções psicológicas. Neste aspecto, discutimos aqui: 1) cinco técnicas comuns da abordagem comportamental-cognitiva (técnicas de relaxamento, operantes, cognitivas, de treinamento social e de aceitação; 2) o programa de treino de atividades operantes e 3) um caso clínico ilustrando a aplicação deste programa

Is America Ready for a Humane Feral Pig Toxicant?

In 2005 the Invasive Animals Cooperative Research Centre undertook an extensive literature review in an attempt to discover possible pharmacological weaknesses of pigs that could be inherently targeted with specific chemicals. For a chemical to have utility it ideally had to be: safe for human operators, highly toxic to pigs, bait deliverable, target specific, humane, residue-less, reversible, inexpensive, already registered for other purposes, patentable, acceptable to trading partners, and have a well documented toxicological profile. Numerous weaknesses and associated candidate chemicals were discovered, but only one, sodium nitrite, proved appropriate in gavage and bait delivery proof-of-concept pen trials. This paper details the discovery process, two years of research towards formulating an article-of-commerce, and three years of development and registration. Discussed is what is required in relation to lobbying and funding, dealing with bureaucracy, intellectual property protection, formulation, target-specificity and nontarget safety, humaneness, ground and aerial baiting field efficacy, product stability, environmental fate and residue data in order to register a commonly available human food preservative as a new vertebrate pesticide in Australia. Also discussed is the development of a novel bait delivery device that increases the target-specificity and cost-efficiency of feral pig control

Limit Theorems for Estimating the Parameters of Differentiated Product Demand Systems

We provide an asymptotic distribution theory for a class of Generalized Method of Moments estimators that arise in the study of differentiated product markets when the number of observations is associated with the number of products within a given market. We allow for three sources of error: the sampling error in estimating market shares, the simulation error in approximating the shares predicted by the model, and the underlying model error. The limiting distribution of the parameter estimator is normal provided the size of the consumer sample and the number of simulation draws grow at a large enough rate relative to the number of products. We specialise our distribution theory to the Berry, Levinsohn, and Pakes (1995) random coefficient logit model and a pure characteristic model. The required rates differ for these two frequently used demand models. A small Monte Carlo study shows that the difference in asymptotic properties of the two models are reflected in the models’ small sample properties. These differences impact directly on the computational burden of the two models

Sleep problems in pain patients entering tertiary pain care : the role of pain-related anxiety, medication use, self-reported diseases, and sleep disorders

Peer reviewe

Employer Policies and Practices to Manage and Prevent Disability: Foreword to the Special Issue

Purpose Employer policies and practices have been shown to impact workplace disability, but research in this area has waned in recent years despite an aging workforce, a growing prevalence of chronic health conditions, and a larger proportion of working-age adults on permanent work disability in many jurisdictions. The purpose of this article is to describe the background rationale and methodology for an invited conference designed to improve research of employer strategies to curtail work disability. Methods A multidisciplinary team of 26 international researchers with published research in employer-based disability management or related fields were invited to attend a 3-day conference in Hopkinton, Massachusetts, USA. The overall goal was to review the status of current research of workplace disability management and prevention, examine its relevance for employer decision-making, compare conceptual frameworks or theoretical perspectives, and recommend future research directions. Working groups were organized and draft manuscripts were prepared in advance. Conference activities included working group presentations and critiques, discussions with a panel of industry consultants and advisors, group interaction and debate, generation of final recommendations, and manuscript revision. Results/Conclusion Six principal domains were established with respect to future research: (a) further elucidation of the key workplace factors that buffer the disabling effects of injury and illness; (b) more innovative and feasible options for workplace intervention; (c) measurement of workplace-relevant disability outcomes; (d) a stronger theoretical framework for understanding the factors behind employer uptake and implementation; (e) a focus on special clinical populations and occupations where disability risk is most troubling; and (f) better representation of workers and employers that reflect the diverse and changing nature of work. Final comments and recommendations of the working groups are presented in the following six articles in this special issue of the Journal of Occupational Rehabilitation. Conference attendees recommended changes in methodology, collaboration strategies, and theoretical perspectives to improve the practical and scientific impact of future research of employer practices