Extended generalised Pareto models for tail estimation

The most popular approach in extreme value statistics is the modelling of threshold exceedances using the asymptotically motivated generalised Pareto distribution. This approach involves the selection of a high threshold above which the model fits the data well. Sometimes, few observations of a measurement process might be recorded in applications and so selecting a high quantile of the sample as the threshold leads to almost no exceedances. In this paper we propose extensions of the generalised Pareto distribution that incorporate an additional shape parameter while keeping the tail behaviour unaffected. The inclusion of this parameter offers additional structure for the main body of the distribution, improves the stability of the modified scale, tail index and return level estimates to threshold choice and allows a lower threshold to be selected. We illustrate the benefits of the proposed models with a simulation study and two case studies.     

Partial Round-Robin Comparisons with Perfect Rankings

In teaching the development of uniformly most powerful unbiased (UMPU) tests, one rarely discusses the performance of alternative biased tests. It is shown, through the comparison of two independent Bernoulli proportions, that a biased test (the Z test) can be more powerful than the UMPU test (Fisher's exact test—randomized) in a large region of the alternative parameter space. A more general example is also given.     

Confidence Intervals for Univariate Impulse Responses With a Near Unit Root

This article proposes a method for constructing confidence intervals for the impulse response function of a univariate time series with a near unit root. These confidence intervals control coverage, whereas the existing techniques can all have coverage far below the nominal level. I apply the proposed method to several measures of U.S. aggregate output.     

British Constructions with Constitutions: The Formal and Informal Nature of 'Island' Relations on Montserrat and Gibraltar

This article explores social, economic and political relations on two British Dependent Territories (BDTs) -- Montserrat and Gibraltar. This article notes that though BDTs are British colonial constructions, created, sustained and modelled upon and by Britain, they differ from Britain in that they have political constitutions. They also exhibit an ambiguous dependence and independence upon and with Britain. This article goes on to look at social and economic relations on Montserrat and Gibraltar before comparing and contrasting the political climates on each BDT. Throughout this article, it is suggested that there is a dynamic tension between formal and informal aspects to managing life. Finally, this article concludes with a discussion about the suitability of the split between Executive and Legislative Councils in these two BDTs.     

Racism in three dimensions: South African architecture and the ideology of white superiority

What has been the effect of three hundred and fifty years of colonialism and apartheid on South African architecture? What role has architecture played in reinforcing and perpetuating racist ideology? Can a building or a space be racist? Racism in Three Dimensions explores these questions and others pertaining to the relationship between race, racism and architecture in post‐apartheid South Africa and seeks to define a role for the architectural profession in the struggle to heal the wounds of apartheid     

Nationalism versus civilisations: an assessment of alternate theories on the future of ethnic identity and conflict

The end of the Cold War has caused a reassessment of the future basis for conflict and identity. While Samuel Huntington predicts that super-national ‘civilisations’ are becoming the basis for identity and conflict, many dispute this arguing that either past ethnic and national bases for identity and conflict will remain the norm or that world integration and interdependence will cause the world to unite. This article examines an aspect of this debate using data on ethnic conflict from the Minorities at Risk data set, as well as data collected independently. Specifically, it assesses whether post-Cold War ethnic conflict, and by inference ethnic identity, is more influenced by civilisational or ethnic variables. The analysis shows that separatism, a nationalist variable, is considerably more strongly associated with ethnic rebellion than are civilisational differences. Furthermore, in the multi-variate analysis civilisational differences are, if anything, associated with less ethnic rebellion. Also, separatism and various political variables more strongly influence ethnic rebellion than do civilisational differences. Thus, this study strongly supports the contention that, at least as of the late 1990s, identity continues to be based on national end ethnic factors rather than civilisational ones.     

The Skilled Wage Premium and the Growth of Small Firms in UK Manufacturing

We document the role of small firms in explaining the growth of the skilled/unskilled wage premium in UK manufacturing over the 1980s. Our major findings are (i) the share of manufacturing employment in small firms' (0–99) employees has risen by 35 percent over this period; (ii) small firms pay more unequal wages than do large firms: the non-manual/manual wage premium is 1.53 in small firms and 1.50 in firms of over 1,500 workers; (iii) the growth in small firms over the period explains about 20 percent of the rise in the skilled/unskilled wage premium.     

Ackoff's Fables revisited: stories to inform operational research practice

This paper considers Ackoff's Fables, a set of short stories published by Ackoff in 1978 as guides to creative problem solving. The paper argues that storytelling of this kind contributes usefully to management and MS/OR education, before addressing how such Fables might be interpreted. It is demonstrated, using one of Ackoff's Fables, The Smart Jackass, for illustrative purposes, that interpretation of even apparently straightforward stories such as these is not unambiguous. The Fables can be interpreted in a multitude of different and sometimes contradictory ways, and the truths they might contain are not self-evident. Yet, as the basis for discussion, they still have much to offer as educational tools. The paper concludes with a discussion of literal truth in stories, and presents a classification of story types according to their relationship to literal truth.     

Visualization for Large‐scale Gaussian Updates

In geostatistics and also in other applications in science and engineering, it is now common to perform updates on Gaussian process models with many thousands or even millions of components. These large‐scale inferences involve modelling, representational and computational challenges. We describe a visualization tool for large‐scale Gaussian updates, the ‘medal plot’. The medal plot shows the updated uncertainty at each observation location and also summarizes the sharing of information across observations, as a proxy for the sharing of information across the state vector (or latent process). As such, it reflects characteristics of both the observations and the statistical model. We illustrate with an application to assess mass trends in the Antarctic Ice Sheet, for which there are strong constraints from the observations and the physics.