Effects of unmeasured heterogeneity in the linear transformation model for censored data

We investigate the effect of unobserved heterogeneity in the context of the linear transformation model for censored survival data in the clinical trials setting. The unobserved heterogeneity is represented by a frailty term, with unknown distribution, in the linear transformation model. The bias of the estimate under the assumption of no unobserved heterogeneity when it truly is present is obtained. We also derive the asymptotic relative efficiency of the estimate of treatment effect under the incorrect assumption of no unobserved heterogeneity. Additionally we investigate the loss of power for clinical trials that are designed assuming the model without frailty when, in fact, the model with frailty is true. Numerical studies under a proportional odds model show that the loss of efficiency and the loss of power can be substantial when the heterogeneity, as embodied by a frailty, is ignored. An erratum to this article can be found at     

A computationally simple bivariate survival estimator for efficacy and safety

Both treatment efficacy and safety are typically the primary endpoints in Phase II, and even in some Phase III, clinical trials. Efficacy is frequently measured by time to response, death, or some other milestone event and thus is a continuous, possibly censored, outcome. Safety, however, is frequently measured on a discrete scale; in Eastern Cooperative Oncology Group clinical trial E2290, it was measured as the number of weekly rounds of chemotherapy that were tolerable to colorectal cancer patients. For the joint analysis of efficacy and safety, we propose a non-parametric, computationally simple estimator for the bivariate survival function when one time-to-event is continuous, one is discrete, and both are subject to right-censoring. The bivariate censoring times may depend on each other, but they are assumed to be independent of both event times. We derive a closed-form covariance estimator for the survivor function which allows for inference to be based on any of several possible statistics of interest. In addition, we derive its covariance with respect to calendar time of analysis, allowing for its use in sequential studies.     

Is the Study of Happiness a Worthy Scientific Pursuit?

This paper critiques the view that the study of happiness is not a worthy scientific pursuit. The happiness set point and hedonic treadmill theories denote the complexity of increasing happiness levels due to genetic limitations and adaptation, however, there is mounting evidence to suggest that with the use of appropriate measures and specific interventions aimed at fostering strengths and virtues, happiness can be increased. Furthermore, the benefits of investigating methods for increasing happiness include improvements in physical, psychological and social health and well-being. It is concluded that approaching human needs from a top down or holistic standpoint where individuals can use their strengths to overcome life’s challenges, is beneficial to health and well-being. Hence, the study of happiness is a worthy scientific pursuit.     

Does Society Matter? Life Satisfaction in the Enlarged Europe

Life satisfaction is quite heterogeneously distributed across countries of the enlarged European Union. Previous research has shown how living conditions within individual countries, such as access to material and emotional resources, are important for personal well-being, but it has been less successful in explaining differences between countries. This article investigates whether it matters in which political and economic circumstances people live, as well as whether their particular perception of the quality of their societal environment plays a role. People are well aware that the institutional and cultural settings in which their lives are embedded create opportunities and limitations: within individual countries, perceptions of society influence life satisfaction outcomes irrespective of access to resources. However, their importance for well-being differs across Europe: perceptions of societies are highly decisive in countries that provide only a minimum of social security and in which the reliability of political institutions is poor. In rich and stable countries, the impact is weaker and private social support becomes more important. In addition to these country-specific weights of life satisfaction determinants, life satisfaction variations between countries can be explained to a large extent by taking into consideration the economic performance, the social security level, and the political culture in a country—all in all, general conditions that enable people to live a respectable life.     

The Extent of Economic Vulnerability in the Canadian Labour Market and Federal Jurisdiction: Is There a Role for Labour Standards?

This paper characterizes vulnerable workers in Canada and the federal jurisdiction, based upon characteristics such as employment status, demographic characteristics, and job characteristics, and identifies areas in which labour standards may have a role. Based on this analysis, the paper evaluates the potential for labour standards to address economic vulnerability, focusing on labour standards policies aimed at wages and benefits, hours, and employment arrangements. In addition, the analysis considers the extent to which labour standards are likely to reach vulnerable workers. The results suggest several potential roles for labour standards and highlights policy implications.

Is demography destiny? The role of structural and demographic factors in Australis past and future labour supply

Following the release of the Intergenerational Report, the Australian Treasury identified the levers to address the economic effects of demographic ageing as ‘the three Ps’: population, participation and productivity. To date, the first ‘P’, population, has been treated as an exogenous factor, with the common view being that there is very little that the government can do to supplant demographic ageing. Focusing upon labour supply, this paper shows how variation in Australia’s underlying demography can significantly alter Australia’s future labour supply. Although governments cannot redirect the cohort flow component of population ageing, much can be achieved in promoting growth of the labour supply by maintaining or increasing fertility (in the longer term), or increasing targeted migration (in the short to medium term). This paper also decomposes the relative role of cohort flow, changing demography and changing labour force participation on the growth of the labour supply over the past 20 years. Over this period, the entry of the baby boom generation (cohort flow) and increased labour force participation of women accounted for almost all of the growth in the labour force. Changing demography had very little effect. However, Australias future labour supply will not include a large increase in cohort flow (as caused by the baby boomers) or a very large increase in female labour force participation. Regardless of the assumptions used, labour supply growth will be considerably lower in the next and subsequent 20 years, when compared to the previous 20.     

HIV testing,perceptions of AIDS risk,and condom use motivation among US women

As STD infections including HIV increase in the United States, it has become increasingly important to policy makers to ascertain the extent to which knowledge and perceptions of AIDS risk affect an individual's probability of altering their sexual or contraceptive behavior to avoid infection. This paper examines the extent to which women's perceptions of their own and their partners' risk of HIV infection affects the probability of using a condom for protection against sexually transmitted diseases. This paper also examines the extent to which HIV testing may affect motivation for condom use. Crosstabulations reveal that prophylactic condom use is more prevalent among women who have been tested for HIV and increase as perceptions of their chance (and their partner's chance) of being positive increases. The multivariate results from this study indicate that having an HIV test significantly predicts the likelihood of using a condom for STD prevention for US women. Furthermore, women who perceive themselves to be at least somewhat likely to be HIV positive have a higher probability of using a condom to prevent sexually transmitted disease, and women who perceive their partners to be HIV positive are twice as likely as other women to use a condom for STD prevention. However, women who consider themselves likely to be HIV positive are no more likely to use a condom than those who consider themselves not at risk.     

Regional variation in acceptance of Indonesia's family planning program

Indonesia's family planning program is regarded as a major success.Survey data from 1997 reveal that rates of contraceptive use vary dramatically amongIndonesia's 27 provinces, from a high of 67 percent of ever married women currently using contraceptives in the province of North Sulawesi, to a low of 19 percent current users in East Timor and28 percent in Aceh. This study uses both a quantitative analysis of the 1997 Indonesia Demographic and Health Survey, and a qualitative study carried out in July of 2000 to understand regionalvariation. The study identified a small number of factors that show a clear relation with levels of contraceptive use. Media exposure and education are the strongest and most consistent predictors of levels of contraceptive use, and appear to be the surest strategies for promoting family change. But the study also showed that the process of social change is subjectto culturally and historically specific local factors whose presence and importance is difficult to predict. Our study of regional variation in contraceptive use illustrates the range and complexityof obstacles faced by Indonesia's leaders in attempting to forge a single nation fromsuch a diverse and far-flung population. Although the creation of Indonesia in the space of just half a century is a monumental achievement, the project is clearly not yet complete.