Procrustes shape analysis of triangulations of a two coloured point pattern

Consider a set of points in the plane with Gaussian perturbations about a regular mean configuration in which a Delaunay triangulation of the mean of the process is comprised of equilateral triangles of the same size. The points are labelled at random as black or white with variances of the perturbations possibly dependent on the colour. By investigating triangle subsets (with four sets of possible colour labels for the vertices) in detail we propose various test statistics based on a Procrustes shape analysis. A simulation study is carried out to investigate the relative merits and the adequacy of the approximations used in the distributional results, as well as a comparison with simulation methods based on nearest-neighbour distances. The methodology is applied to an investigation of regularity in human muscle fibre cross-sections.     

Block diagrams and splitting criteria for classification trees

Various aspects of the classification tree methodology of Breiman et al., (1984) are discussed. A method of displaying classification trees, called block diagrams, is developed. Block diagrams give a clear presentation of the classification, and are useful both to point out features of the particular data set under consideration and also to highlight deficiencies in the classification method being used. Various splitting criteria are discussed; the usual Gini-Simpson criterion presents difficulties when there is a relatively large number of classes and improved splitting criteria are obtained. One particular improvement is the introduction of adaptive anti-end-cut factors that take advantage of highly asymmetrical splits where appropriate. They use the number and mix of classes in the current node of the tree to identify whether or not it is likely to be advantageous to create a very small offspring node. A number of data sets are used as examples.     

The rhetorical construction of efficiency: Restructuring and industrial democracy in Mondragón,Spain

This paper examines the tension between the struggle to survive in a competitive economy and efforts to create more democratic workplaces in the Basque worker cooperative complex in Mondragón, Spain. Data from archival research, participant observation, and interviews are used to outline the historical context of structural change and policy-making in the complex. Language used in internal policy discussions is analyzed to explore the way in which arguments about efficiency have shaped interpretations of structural change and these organizations' policy responses. It is argued that in these cooperatives, the concept of efficiency does not operate as a neutral, objective benchmark of organizational performance, but is socially and rhetorically constructed. The predominant approach to efficiency that is emerging in Mondragón aims to make the cooperatives more competitive, but also facilitates a gradual displacement of collectively established organizational objectives such as relative equality, job security, and favorable work conditions for ones that privilege institutional interests of profitability and stability. More importantly, it has helped usher in important changes in the policy-making process itself, limiting the range of legitimate participation and weakening broad-based control over the identification of appropriate objectives and means. The paper suggests that reframing an existing rhetorical strategy to highlight more clearly the link between efficiency and any given set of objectives would stimulate a broader discussion of policy issues and help balance more effectively the diverse interests at stake in Mondragón's restructuring.An earlier version of this paper was presented at the 1992 annual meetings of the American Sociological Association in Pittsburgh, Pennsylvania.     

Racial and Ethnic Variation in the Relationship Between Student Loan Debt and the Transition to First Birth

The present study employs discrete-time hazard regression models to investigate the relationship between student loan debt and the probability of transitioning to either marital or nonmarital first childbirth using the 1997 National Longitudinal Survey of Youth (NLSY97). Accounting for nonrandom selection into student loans using propensity scores, our study reveals that the effect of student loan debt on the transition to motherhood differs among white, black, and Hispanic women. Hispanic women holding student loans experience significant declines in the probability of transitioning to both marital and nonmarital motherhood, whereas black women with student loans are significantly more likely to transition to any first childbirth. Indebted white women experience only a decrease in the probability of a marital first birth. The results from this study suggest that student loans will likely play a key role in shaping future demographic patterns and behaviors.     

Organizational Pathways for Social Innovation and Societal Impacts in Disability Nonprofits

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - Using data from a sample of 301 Australian disability nonprofit organizations (NPOs), this study applies configurational...     

Parental Status and Biological Functioning: Findings from the Nashville Stress and Health Study

Population Research and Policy Review - Does childrearing affect the biological functioning of parents? To address this question, we analyze cross-sectional survey and biomarker data from...     

Widening the gap: White ignorance,race relations and the consequences for Aboriginal people in Australia

White ignorance has a critical impact on race relations and is implicated in the maintenance of Aboriginal disadvantage. Addressing this ignorance is a largely overlooked capacity-building opportunity within Australia's non-Aboriginal population. It warrants consideration as a key component of strategies targeting Aboriginal disadvantage. Despite the established links between race relations and Aboriginal well-being, Aboriginal perspectives on non-Aboriginal people rarely feature in public discourse on “Aboriginal problems.” This paper draws on data from 180 in-depth interviews with 44 Aboriginal people in Darwin on the topic of White Australian people, culture and race relations. It reports Aboriginal perceptions of White Australian ignorance across areas of great symbolic and practical significance to Aboriginal people's lives. Their experience is that most White Australians are ignorant of the history of colonisation and the complexities of its aftermath. They are ignorant of Aboriginal law, cultures and languages, and of the extent of their own ignorance. The call to address White ignorance subverts assumptions about whose ignorance and capacity must be dealt with in order to progress national goals of reconciliation, address Aboriginal disadvantage and achieve justice and equality for Aboriginal people.     

Private security,maritime piracy and the provision of international public safety

Journal of Risk and Uncertainty - Private solutions to personal protection and property rights often evolve in environments that are weakly institutionalized. In this vein, we examine the effect of...     

Forecasting Value at Risk and Expected Shortfall Using a Semiparametric Approach Based on the Asymmetric Laplace Distribution

Value at Risk (VaR) forecasts can be produced from conditional autoregressive VaR models, estimated using quantile regression. Quantile modeling avoids a distributional assumption, and allows the dynamics of the quantiles to differ for each probability level. However, by focusing on a quantile, these models provide no information regarding expected shortfall (ES), which is the expectation of the exceedances beyond the quantile. We introduce a method for predicting ES corresponding to VaR forecasts produced by quantile regression models. It is well known that quantile regression is equivalent to maximum likelihood based on an asymmetric Laplace (AL) density. We allow the density's scale to be time-varying, and show that it can be used to estimate conditional ES. This enables a joint model of conditional VaR and ES to be estimated by maximizing an AL log-likelihood. Although this estimation framework uses an AL density, it does not rely on an assumption for the returns distribution. We also use the AL log-likelihood for forecast evaluation, and show that it is strictly consistent for the joint evaluation of VaR and ES. Empirical illustration is provided using stock index data. Supplementary materials for this article are available online.