A stochastic recurrence equations approach for score driven correlation models

We describe stationarity and ergodicity (SE) regions for a recently proposed class of score driven dynamic correlation models. These models have important applications in empirical work. The regions are derived from sufficiency conditions in Bougerol (1993 Bougerol, P. (1993). Kalman filtering with random coefficients and contractions. SIAM Journal on Control and Optimization 31(4):942–959.[Crossref], [Web of Science ®] , [Google Scholar]) and take a nonstandard form. We show that the nonstandard shape of the sufficiency regions cannot be avoided by reparameterizing the model or by rescaling the score steps in the transition equation for the correlation parameter. This makes the result markedly different from the volatility case. Observationally equivalent decompositions of the stochastic recurrence equation yield regions with different shapes and sizes. We use these results to establish the consistency and asymptotic normality of the maximum likelihood estimator. We illustrate our results with an analysis of time-varying correlations between U.K. and Greek equity indices. We find that also in empirical applications different decompositions can give rise to different conclusions regarding the stability of the estimated model.     

Economic Factors and Relationship Quality Among Young Couples: Comparing Cohabitation and Marriage

Are economic resources related to relationship quality among young couples, and to what extent does this vary by relationship type? To answer these questions, we estimated regression models predicting respondent reports of conflict and affection in cohabiting and married partner relationships using the National Longitudinal Study of Youth, 1997 (NLSY97, N = 2,841) and the National Longitudinal Study of Adolescent Health (Add Health, N = 1,702). We found that economic factors are an important predictor of conflict for both married and cohabiting couples. Affection was particularly responsive to human capital rather than short‐term economic indicators. Economic hardship was associated with more conflict among married and cohabiting couples.     

Approximation algorithms for <Emphasis Type="Italic">k</Emphasis>-level stochastic facility location problems

In the k-level facility location problem (FLP), we are given a set of facilities, each associated with one of k levels, and a set of clients. We have to connect each client to a chain of opened facilities spanning all levels, minimizing the sum of opening and connection costs. This paper considers the k-level stochastic FLP, with two stages, when the set of clients is only known in the second stage. There is a set of scenarios, each occurring with a given probability. A facility may be opened in any stage, however, the cost of opening a facility in the second stage depends on the realized scenario. The objective is to minimize the expected total cost. For the stage-constrained variant, when clients must be served by facilities opened in the same stage, we present a \((4-o(1))\)-approximation, improving on the 4-approximation by Wang et al. (Oper Res Lett 39(2):160–161, 2011) for each k. In the case with \(k=2,\,3\), the algorithm achieves factors 2.56 and 2.78, resp., which improves the \((3+\epsilon )\)-approximation for \(k=2\) by Wu et al. (Theor Comput Sci 562:213–226, 2015). For the non-stage-constrained version, we give the first approximation for the problem, achieving a factor of 3.495 for the case with \(k = 2\), and \(2k-1+o(1)\) in general.     

An Intuitive Geometric Approach to the Gauss Markov Theorem

Algebraic proofs of Gauss–Markov theorem are very disappointing from an intuitive point of view. An alternative is to use geometry that emphasizes the essential statistical ideas behind the result. This article presents a truly geometrical intuitive approach to the theorem, based only in simple geometrical concepts, like linear subspaces and orthogonal projections.     

Technology Use and Performance: A Field Study of Broker Workstations*

Organizations invest in technology with the expectation that it will contribute to performance, and members of the organization must use technology for it to make a contribution. For this reason, it is important for managers and designers to understand and predict system use. This paper develops a model of workstation use in a field setting where the use of the system is an integral part of the user's job. The model is based on the Technology Acceptance Model (TAM), which we extended to include social norms, user performance, and two control variables. Brokers and sales assistants in the privateclient group of a major investment bank provided data to test our extended model. The core perception variables in TAM do not predict use in this study. Social norms and one's job requirements are more important in predicting use than workers' perceptions about ease of use and usefulness. The paper discusses the implications of these findings and suggests directions for future research.     

An avian urban morphotype: how the city environment shapes great tit morphology at different life stages

Urban Ecosystems - Urbanization is a worldwide phenomenon associated with tremendous modifications of natural habitats. Understanding how city dwelling species are affected by those changes is...     

Public Perception of "Who is a Volunteer": An Examination of the Net-Cost Approach from a Cross-Cultural Perspective

Our aim is to enhance the knowledge regarding how the public assess and rate volunteerism. We begin by first developing the model for understanding the potential use of the net-cost concept in eliciting the public's subjective perceptions on the extent to which certain activities are perceived as volunteerism. Four hypotheses relevant to the use of the net-cost concept are developed. We developed a questionnaire consisting of 50 case scenarios and applied it in Canada, India, Italy, Netherlands, and Georgia and Philadelphia in the United States, each with a sample of 450 adults or more. With one exception, our net-cost hypotheses are supported, suggesting that the public perception of volunteering is strongly linked with the costs and benefits that accrue to the individual from the volunteering activity, and that this result holds true across different cultures. Finally, we suggest directions for future research that can shed further light on the relationship between net cost and public good.     

A children's space? Participation in multi‐agency early intervention

The common assessment framework provides a model of early intervention, which is familiar in local authorities throughout England, and asserts a participatory framework of child and family engagement. This article draws on data from a research project undertaken in 1 local authority in the Midlands of England, to explore the experiences of children, young people, and their families, who were engaged in the process of multi‐agency early intervention. The article considers the young people's involvement, including their accounts of attending common assessment framework meetings, and their engagement by practitioners. The research found that young people's participation was limited. The findings suggest that this is, in part, a response to disciplinary discourses around schooling and attendance. In addition, the narratives of parents and young people showed that under‐resourcing of work with young people meant that the time taken to build relationships and engage them in a process of self‐assessment, planning, and decision making was constrained and rationed. The article concludes that to achieve a participatory children's space, an active and more engaged model of childhood needs to be facilitated by practitioners and parents outside the school‐dominated space found in this study.     

‘Nomadic’ organization and the experience of journeying: Through liminal spaces and organizing places

This paper explores the author's experience of ‘nomadic’ organization [Deleuze, G., and F. Guattari. 1988. A Thousand Plateaus. London: Continuum] through the findings of an ethnographic study of an annual folk-culture community festival in a rural region of Sweden. The study concerned the practices of one small village community organizing group, of which the author was a member, in contributing to the festival. Using autoethnographic methods, the author brings together phenomenological theories of embodied knowledge [Merleau-Ponty, M. 1962. The Phenomenology of Perception. Abingon: Routledge; Küpers, W. 2011. “Dancing on the Līmen – Embodied and Creative Inter-Places as Thresholds of Be(com)ing: Phenomenological Perspectives on Liminality and Transitional Spaces in Organisation and Leadership.” Tamara – Journal for Critical Organization Inquiry Special Issue on Liminality 9 (3–4): 45–59.] and process theories or organizing [Chia, R. 1999. “A Rhizomic Model of Organizational Change and Transformation: Perspective from a Metaphysics of Change.” British Journal of Management 10 (2): 209–227; Tsoukas, H., and R. Chia. 2002. “On Organizational Becoming: Rethinking Organizational Change.” Organization Science 13 (5): 567–582] to examine his experiences of nomadic ‘journeying’. This highlights his movement in and through liminal spaces, both physical and metaphorical, as part of the research project, and his engagement with fellow participants in the co-construction of a place as part of the festival site organization. The impacts of these experiences on the author and their implications for the spatial relations of organizing are examined using fragments of reflexion, incorporating photographic and poetic elements.