Gender‐ and Age‐Related Differences in the Association Between Social Relationship Quality and Trait Levels of Salivary Cortisol

The majority of studies linking individual differences in the quality of social relationships and activity of the hypothalamic‐pituitary‐adrenal (HPA) axis have focused on the early development of attachment between infants and their caregivers. Later in development, during middle childhood and adolescence, the parallel HPA links to age‐appropriate social relationships with peers, parents, and siblings remain largely unspecified. This study addressed this knowledge gap. Early morning saliva samples were obtained from 367 children in middle childhood (ages 6–10) and 357 adolescents (M age=11–16 years) on two successive days 1 year apart and assayed for cortisol. Latent state–trait modeling was employed to separate variance in cortisol levels attributable to “stable trait‐like” versus “state or situational specific” sources to minimize the high moment‐to‐moment variation in basal adrenocortical activity. During adolescence but not middle childhood, and for girls but not boys, lower levels of “trait cortisol” were associated with poor quality social relationships. The pattern was robust, extending to the quality of relationships with parents, siblings, and peers. Importantly, the relationship was independent of the rates of internalizing or externalizing problem behavior. We found that isolating the variance in cortisol levels attributable to stable intrinsic sources revealed an interpretable pattern that linked individual differences in basal HPA activity to social relationships during adolescence. Studies are needed to reveal the biosocial mechanisms involved in the establishment of this gender‐ and age‐specific phenomenon and to decipher whether or not individual differences in this hormone‐behavior link are adaptive.     

Multiple Imputation of Missing or Faulty Values Under Linear Constraints

Many statistical agencies, survey organizations, and research centers collect data that suffer from item nonresponse and erroneous or inconsistent values. These data may be required to satisfy linear constraints, for example, bounds on individual variables and inequalities for ratios or sums of variables. Often these constraints are designed to identify faulty values, which then are blanked and imputed. The data also may exhibit complex distributional features, including nonlinear relationships and highly nonnormal distributions. We present a fully Bayesian, joint model for modeling or imputing data with missing/blanked values under linear constraints that (i) automatically incorporates the constraints in inferences and imputations, and (ii) uses a flexible Dirichlet process mixture of multivariate normal distributions to reflect complex distributional features. Our strategy for estimation is to augment the observed data with draws from a hypothetical population in which the constraints are not present, thereby taking advantage of computationally expedient methods for fitting mixture models. Missing/blanked items are sampled from their posterior distribution using the Hit-and-Run sampler, which guarantees that all imputations satisfy the constraints. We illustrate the approach using manufacturing data from Colombia, examining the potential to preserve joint distributions and a regression from the plant productivity literature. Supplementary materials for this article are available online.     

The Impact of Neo-liberalism on South Korea's Public Pension: A Political Economy of Pension Reform

This article examines the recent Korean pension reforms from a political economy perspective. It argues that these reforms are of particular interest because, unlike major pay-as-you-go pension schemes in Europe, the Korean pension scheme is a funded one and, therefore, is subject to market exposure. Also in contrast to the problems that public pension reforms have encountered in European and other OECD countries, especially 'blame avoidance', the more radical Korean reforms were implemented without significant challenge or resistance. First of all, the National Pension Scheme is described prior to the 1997 Asian economic crisis. Then the impact of this crisis on the Korean welfare state and, especially, its pension system are analysed. The main part of the article consists of a political economy of the pension reform process, in which the key roles of the international governmental organizations and the domestic neo-liberal policy elite are pinpointed. This neo-liberal ideology was critical in developing and sustaining an influential discourse on the 'crisis' in Korea's national pension fund. The article concludes by arguing, against the neo-liberal tide, for the inclusion of a pay-as-you-go element in the national pension in order to tackle escalating poverty in old age.     

The effects of demographics, residence and socioeconomic status on the distribution of 19th century Mexican biological living conditions

The use of height data to measure living standards is now a well-established method in economics and the social sciences. However, there are still some populations, places, and times for which anthropometric evidence remains thin. One example is 19th century Mexicans born in Mexico and in the American West. This paper demonstrates that the statures of 19th century Mexicans born in Mexico remained approximately constant, while the statures of Mexicans born in the U.S. increased by nearly 4 cm, indicating that although the two groups shared a common genetic background, their cumulative biological living conditions differed markedly. The BMIs of Mexicans born in Mexico remained constant, and the BMIs of Mexicans born in the U.S. were high initially but rapidly converged in the late 19th century.     

Missing data: Discussion points from the PSI missing data expert group

The Points to Consider Document on Missing Data was adopted by the Committee of Health and Medicinal Products (CHMP) in December 2001. In September 2007 the CHMP issued a recommendation to review the document, with particular emphasis on summarizing and critically appraising the pattern of drop‐outs, explaining the role and limitations of the ‘last observation carried forward’ method and describing the CHMP's cautionary stance on the use of mixed models. In preparation for the release of the updated guidance document, statisticians in the Pharmaceutical Industry held a one‐day expert group meeting in September 2008. Topics that were debated included minimizing the extent of missing data and understanding the missing data mechanism, defining the principles for handling missing data and understanding the assumptions underlying different analysis methods. A clear message from the meeting was that at present, biostatisticians tend only to react to missing data. Limited pro‐active planning is undertaken when designing clinical trials. Missing data mechanisms for a trial need to be considered during the planning phase and the impact on the objectives assessed. Another area for improvement is in the understanding of the pattern of missing data observed during a trial and thus the missing data mechanism via the plotting of data; for example, use of Kaplan–Meier curves looking at time to withdrawal. Copyright © 2009 John Wiley & Sons, Ltd.     

Conditional approval: discussion points from the PSI conditional approval expert group

The European Agency for the Evaluation of Medicinal Products has recently completed the consultation of a draft guidance on how to implement conditional approval. This route of application is available for orphan drugs, emergency situations and serious debilitating or life-threatening diseases. Although there has been limited experience in implementing conditional approval to date, PSI (Statisticians in the Pharmaceutical Industry) sponsored a meeting of pharmaceutical statisticians with an interest in the area to discuss potential issues. This article outlines the issues raised and resulting discussions, based on the group's interpretation of the legislation. Conditional approval seems to fit well with the accepted regulatory strategy in HIV. In oncology, conditional approval may be most likely when (a) compelling phase II data are available using accepted clinical outcomes (e.g. progression/recurrence-free survival or overall survival) and Phase III has been planned or started, or (b) when data are available using a surrogate endpoint for clinical outcome (e.g. response rate or biochemical measures) from a single-arm study in rare tumours with high response, compared with historical data. The use of interim analyses in Phase III for supporting conditional approval raises some challenging issues regarding dissemination of information, maintenance of blinding, potential introduction of bias, ethics, switching, etc.     

Discretionary Time of Chinese College Students: Activities and Impact of SARS-Induced Constraints on Choices

How people make choices about activity engagement during discretionary time is a topic of increasing interest to those studying quality of life issues. Assuming choices are made to maximize individual welfare, several factors are believed to influence these choices. Constraints theory from the leisure research literature suggests these choices are heavily influenced by intrapersonal, interpersonal and structural constraints. Within these constraints, the individual is motivated to make choices that maximize perceived personal welfare. Leisure affordance theory focuses on these motivations by suggesting the importance of more positive influences on choices within a set of constraints. In this study, an inventory of discretionary time activities and reasons for choosing these activities were documented for a sample of Chinese college students. Because data were collected during an unanticipated SARS epidemic, the impact of the SARS crisis on students’ daily choices was also examined in detail. Despite the constraints imposed by SARS and the attendant suspension of off-campus activities, some students did not perceive a change of daily life as a result, while others perceived positive changes in attitudes and behavior. Findings shed light on students’ experiences during a time of rapid change in Chinese society and higher education. Decisions made during this influential time of life are important because they may affect students’ future choices related to leisure and discretionary time.     

Theory of population and modern economic analysis. II

A previous article showed that it was possible to make the Malthusian analysis of population more general without abandoning its original framework. The second article examines the underlying assumptions of the analysis more closely in the light of contemporary economic theories, and considers its application to world population problems.