Random regression models for human immunodeficiency virus ribonucleic acid data subject to left censoring and informative drop-outs

Objectives in many longitudinal studies of individuals infected with the human immunodeficiency virus (HIV) include the estimation of population average trajectories of HIV ribonucleic acid (RNA) over time and tests for differences in trajectory across subgroups. Special features that are often inherent in the underlying data include a tendency for some HIV RNA levels to be below an assay detection limit, and for individuals with high initial levels or high ranges of change to drop out of the study early because of illness or death. We develop a likelihood for the observed data that incorporates both of these features. Informative drop-outs are handled by means of an approach previously published by Schluchter. Using data from the HIV Epidemiology Research Study, we implement a maximum likelihood procedure to estimate initial HIV RNA levels and slopes within a population, compare these parameters across subgroups of HIV-infected women and illustrate the importance of appropriate treatment of left censoring and informative drop-outs. We also assess model assumptions and consider the prediction of random intercepts and slopes in this setting. The results suggest that marked bias in estimates of fixed effects, variance components and standard errors in the analysis of HIV RNA data might be avoided by the use of methods like those illustrated.     

Life cycles of growing organizations: A review with implications for knowledge and learning

Conceptualizing growth trajectories of organizations in organismic terms describing transitions through a series of stages, from birth to maturity, has considerable intuitive appeal. Recently, the assumptions underpinning the life‐cycle perspective (growth is linear, sequential, deterministic and invariant) have been argued not to pertain to organizations. This paper reviews the literature on life‐cycle growth models, traces the development of a growing sophistication of conceptualizing growth and highlights some of the limitations of the literature. The authors make a contribution by proposing an alternative conceptual framework for thinking about growing businesses. The framework consists of two dimensions. First, a typology of key issues that are likely to be faced by all growing firms, and the discussion is shaped by M. Gladwell's (The Tipping Point: How Little Things Can Make a Big Difference. Boston: Little Brown, 2000) notion of ‘tipping points’. The second dimension is developed by drawing on the knowledge management literature and the concept of absorptive capacity ( Cohen, W.M. and Levinthal, D.A. (1990 ). Absorptive capacity: a new perspective on learning and innovation. Administrative Science Quarterly, 35 , 128–152). This concept is applied to a discussion of the state of an organization regarding its ability to absorb and use new knowledge. Further, it is suggested that the framework has value for both policy and practice and can be used for the design and specification of interventional support and, to identify and evaluate their impact. If interventions are to help firms to grow, they must provide the right knowledge or support in forms that the firm can utilize. Together, these two dimensions provide a framework to examine firm growth issues and to analyse the effectiveness of different interventions on firms in different states within this framework.     

Corporate planning in local government—a case study

The authors set out their view of the peculiar problems facing corporate planners in local government as compared with the private sector and their view of the nature of corporate planning in this special environment. By way of illustration as to how one local authority has attempted to introduce corporate planning, the article includes a case study of the City of Bradford Metropolitan Council.     

Personalization of Mail Surveys for General Public and Populations with a Group Identity: Results from Nine Studies*

Abstract The effect of personalization on mail survey response rates was examined in nine studies that included 17 comparisons under several research conditions. A study of this variable across multiple experiments in five agricultural experiment stations was undertaken because of conflicting results from previous research and from concern that the effectiveness of personalization might have decreased over time. Results show that, while response to general public surveys appeared to increase modestly across all treatment groups, there was no positive effect for populations in which a group identity (e.g., Dear Oregon Gardner or Dear ATV Owner) is employed to address respondents in cover letters. Personalization appears to remain useful for improving response in surveys of the general public.     

Advertising, Individual Consumption Levels, and the Natural Environment, 1900–2000

One central determinant of global environmental change is the continued expansion of personal consumption levels. In order to more fully understand the relationship between consumption and environmental degradation, the determinants of consumption must first be identified. Prior research in this area has focused on economic factors, primarily personal disposable income and population demographic characteristics. The role of cultural factors, including advertising, has been actively mentioned in theoretical analyses of the driving forces of individual consumption. However, this has not been empirically tested. In this article, we conduct an analysis of the impact of advertising on consumption levels in the United States. We start with a theoretical discussion of the literature on advertising and consumption. Based on this literature, we establish three hypotheses regarding the relationship between advertising expenditure and personal consumption. These hypotheses are then tested using time series analysis over the time period 1900–2000. The results show that advertising significantly impacts overall consumption and that these effects vary by type of consumption. We conclude with a discussion of the implications of this analysis for further research into the driving forces of global environmental change.     

The Number of Times an Anonymous Rule Violates Independence in the 3 × 3 Case

If an anonymous rule f always outputs a transitive relation and satisfies Pareto, then, by Arrow’s theorem, f violates the condition of independence. We give lower and upper bounds for the number of times an anonymous rule violates independence in the case of three alternatives and three voters.     

Early Child Care and the School Readiness of Children from Mexican Immigrant Families1

Combining conceptual models from immigration and educational research, this study investigated whether a normative antecedent to the transition to formal schooling in the contemporary U.S. – early child care – links Mexican immigrant status to various aspects of school readiness. Regression models with nationally representative data revealed that children from Mexican immigrant families were overrepresented in parental care and underrepresented in center‐based care compared to their native peers from other race/ethnic populations, which helped to explain a significant but small portion of their generally lower rates of both math achievement and externalizing symptoms in kindergarten. This mediating role of early child care, however, paled in comparison to family socioeconomic circumstances.