A pattern-mixture odds ratio model for incomplete categorical data

Most models for incomplete data are formulated within the selection model framework. Pattern-mixture models are increasingly seen as a viable alternative, both from an interpretational as well as from a computational point of view (Little 1993, Hogan and Laird 1997, Ekholm and Skinner 1998). Whereas most applications are either for continuous normally distributed data or for simplified categorical settings such as contingency tables, we show how a multivariate odds ratio model (Molenberghs and Lesaffre 1994, 1998) can be used to fit pattern-mixture models to repeated binary outcomes with continuous covariates. Apart from point estimation, useful methods for interval estimation are presented and data from a clinical study are analyzed to illustrate the methods.     

Macro-Economic Factors in Credit Risk Calculations: Including Time-Varying Covariates in Mixture Cure Models

The prediction of the time of default in a credit risk setting via survival analysis needs to take a high censoring rate into account. This rate is because default does not occur for the majority of debtors. Mixture cure models allow the part of the loan population that is unsusceptible to default to be modeled, distinct from time of default for the susceptible population. In this article, we extend the mixture cure model to include time-varying covariates. We illustrate the method via simulations and by incorporating macro-economic factors as predictors for an actual bank dataset.     

All for one or one for all? Authorship and the cross-sectoral valuation of credit in nutrition science

The passionate pursuit of authorships is fuelled by the value they represent to scholars and scientists. This article asks how this value differs across scientists and how these different processes of valuation inform authorship articulation, strategies, and publication behavior in general. Drawing from a qualitative analysis of authorship practices among nutrition scientists employed at universities, contract research organizations, and in food industry, I argue that two different modi operandi emerge when it comes to authorship. These different ways of working produce different collaborative approaches, different credit distribution strategies amongst collaborators, and different value placed upon (the pursuit of) authorship. These different valuation processes are neither explicit nor recognizable to those reading (and judging) author lists. As a consequence, in the politics of authorship, the names standing atop a scientific publication in nutrition science represent different types of value to both the individuals and employing organizations.     

Who does not cut down? Comparing characteristics and drinking motives of drinkers and abstainers during the exam periods

Objective: Drinking alcohol during the exams can affect academic performance and future career options, but is rarely investigated. Drinking motives, sociodemographics and personality characteristics are investigated in nonabstainers and weekly drinkers during the exams. Participants: 7,181 Belgian university students who anonymously responded to an email invitation to an online survey. Methods: Logistic regressions and mixed design analysis of variance on cross-sectional data. Results: One-third of the students continued drinking during the exams, with 40% drinking weekly. Nonabstainers were mainly men, elder, internally motivated when drinking, and housed with parents or independently. Weekly drinkers were similar, except mainly housed in student apartments or independently. Personality characteristics were nonsignificant. All drinking motives were less pronounced during the exams, with smaller differences for internal motives. Conclusions: Mainly linked to internal drinking motives, drinking during the exams in higher education is underestimated. The characteristics and motives of students doing so can be used in future interventions.     

Psychosocial Factors of Migration: Adaptation and Application of the Health Belief Model

Psychosocial factors influencing behaviour play a central role in health research but seem under‐explored in migration research. This is unfortunate because these factors, which include knowledge, attitudes, beliefs, intentions and personality traits, provide essential and potentially effective handles for linking migration and migrant‐integration policies. We demonstrate that the health belief model (HBM) conceptualization of behavioural intentions contributes constructs that can further our understanding of migration intentions, thereby broadening the foundations for migration policies. We adapt the HBM to migration behaviour and then test it empirically by using survey data on international migration from West Africa and the Mediterranean region to the European Union. The results confirm that indicators of “perceived threat to living conditions”, “perceived benefits” and “perceived barriers to migration”, “cues to action” and “self‐efficacy” contribute considerably to the explanation of migration intentions. We conclude that psychosocial factors deserve greater prominence in migration theories and empirical research, and we recommend that migration surveys consider this framework to identify relevant indicators of psychosocial factors of international migration and develop appropriate survey questions to measure them.     

Mass Customization in the Automotive Industry: Comparing Interdealer Trading and Reconfiguration Flexibilities in Order Fulfillment

Mass customization has been viewed as desirable but difficult to achieve in the volume automotive sector. Here we consider flexibility in automotive order fulfillment systems to enhance the ability to satisfy customers with their desired vehicle variants within acceptable delivery lead times. Two types of flexibility are compared in a Virtual‐Build‐to‐Order system—reconfiguration in the planning pipeline and interdealer trading. A representative simulation model is used to investigate the impact of the two types of flexibility across a wide spectrum of product variety levels. The impacts on major stakeholders in the system—the producer, dealers, and customers—are considered. The study shows that both types of flexibilities can bring significant benefits in terms of reductions in lead time and inventory holding. The level of product variety strongly influences the observed effects—an important finding in the mass customization context. Upstream reconfiguration flexibility brings greater benefits than downstream trading flexibility. Reconfiguration tends to dominate trading as a fulfillment mechanism when both are in operation. The findings have implications for the design and management of automotive order fulfillment systems in improving their ability to offer mass customization. The study has relevance for companies in other sectors with high levels of variety that seek to combine efficiency, speed, and flexibility in order fulfillment.     

Adaptive Build-up and Breakdown of Trust: An Agent Based Computational Approach

This article employs Agent-Based Computational Economics (ACE) to investigate whether, and under what conditions, trust is viable in markets. The emergence and breakdown of trust is modeled in a context of multiple buyers and suppliers. Agents develop trust in a partner as a function of observed loyalty. They select partners on the basis of their trust in the partner and potential profit, with adaptive weights. On the basis of realized profits, they adapt the weight they attach to trust relative to profitability, and their own trustworthiness, modeled as a threshold of defection. Trust and loyalty turn out to be viable under fairly general conditions.     

In Search of ‘Managerial Work’: Past,Present and Future of an Analytical Category

Based on a comprehensive review of literature, the paper examines how ‘managerial work’ as a fluid analytical category has been approached methodologically, theoretically and empirically for more than 60 years. In particular, it highlights the existence of competing scholarly understandings regarding its nature, performance, meaning and politics. The authors suggest that subsequent empirical investigations have too often worked, methodologically and theoretically, to slot in, and thus effectively reduce, the term to a particular pre‐existing box, rather than exploring open‐endedly the what and how, but also the why of ‘managerial work’ as a distinct mode of situated ordering. Having represented the concept's past and present by identifying four distinct research approaches reflected in representative publications, the authors suggest that more attention should be devoted to a mode of analytical departure that promises to address directly the suggested shortcomings in the literature. Specifically, it is argued that much could be gained if contemporary notions of practice were brought into the study of managerial work. To this end, the authors outline the contours of a practice‐based approach as a sensitizing framework for understanding managerial work by highlighting the situated, relational, sociomaterial, meaning‐making and consequence‐oriented analytical foci the approach suggests, and suggesting a number of conjoint research questions, as well as acknowledging subsequent limitations.     

Beyond products: new strategic imperatives for developing competencies in dynamic environments

Strategy research has often taken a product-centered perspective. When firms compete in environments characterized by accelerating product life cycles, mass customization, and technological discontinuities, a product-centered perspective on strategy may help explain a firm’s current competitive advantage. However, this perspective adds little guidance in making strategies that create competitive advantage in the future. In this paper, we present a perspective in which dynamic environments require firms to focus on (1) building market-driven, technological, and integration competencies, not a stream of product improvements, and (2) decoupling these competencies from current products in order to create and exploit new opportunities. We discuss the perspective of products as a temporary integration of market and technology trajectories. Research propositions are presented and future implications are discussed.     

A Comparative Study of Segregation Patterns in Belgium,Denmark, the Netherlands and Sweden: Neighbourhood Concentration and Representation of Non-European Migrants

In this paper, we use geo-coded, individual-level register data on four European countries to compute comparative measures of segregation that are independent of existing geographical sub-divisions. The focus is on non-European migrants, for whom aggregates of egocentric neighbourhoods (with different population counts) are used to assess small-scale, medium-scale, and large-scale segregation patterns. At the smallest scale level, corresponding to neighbourhoods with 200 persons, patterns of over- and under-representation are strikingly similar. At larger-scale levels, Belgium stands out as having relatively strong over- and under-representation. More than 55% of the Belgian population lives in large-scale neighbourhoods with moderate under- or over-representation of non-European migrants. In the other countries, the corresponding figures are between 30 and 40%. Possible explanations for the variation across countries are differences in housing policies and refugee placement policies. Sweden has the largest and Denmark the smallest non-European migrant population, in relative terms. Thus, in both migrant-dense and native-born-dense areas, Swedish neighbourhoods have a higher concentration and Denmark a lower concentration of non-European migrants than the other countries. For large-scale, migrant-dense neighbourhoods, however, levels of concentration are similar in Belgium, the Netherlands, and Sweden. Thus, to the extent that such concentrations contribute to spatial inequalities, these countries are facing similar policy challenges.