VARIABLE SELECTION ALONG CANONICAL VECTORS

When describing and displaying inter-group relationships using canonical variate analysis, the question often arises: which variables contribute most to the group separation along particular canonical vectors? This problem is discussed in the context of an example which uses remotely sensed data to discriminate between cover classes. The appropriate between-groups matrix to be input into subset selection procedures is identified. When combined with subsequent simplification of the vectors, the approach leads to a simpler interpretation of the canonical variate display.     

Recent developments in modeling preferences: Uncertainty and ambiguity

In subjective expected utility (SEU), the decision weights people attach to events are their beliefs about the likelihood of events. Much empirical evidence, inspired by Ellsberg (1961) and others, shows that people prefer to bet on events they know more about, even when their beliefs are held constant. (They are averse to ambiguity, or uncertainty about probability.) We review evidence, recent theoretical explanations, and applications of research on ambiguity and SEU.Thanks to Jonathan Baron, James Dow, Peter Fishburn, Itzhak Gilboa, Gordon Hazen, Howard Kunreuther, Tomas Phillipson, David Schmeidler, Amos Tversky, the editor, and several anonymous referees for corrections and helpful comments. Camerer's contribution to this work was supported by the National Science Foundation, grant no. SES 88-09299. Weber's contribution was supported by the Deutsche Forschungsge-meinschaft, grant no. WE 993/5-1.     

Categorical Imperatives: The Interaction of Latino and Racial Identification*

Objective. Most large data sets solicit “ethnic” identification and “racial” identification in separate questions. We test the relative salience of these two identifications by exploring whether individuals who chose both a Latino “ethnic” label and a “racial” label on separate survey questions still chose both of these labels when they were given a single combined question about their racial and ethnic origins. Methods. Using the May 1995 Race and Ethnicity Supplement to the Current Population Survey, we estimate a multinomial logit model of identification choices. Results. We find that most individuals who chose a Latino label and a racial label chose a Latino‐only identification. Selection of multiple labels was more common for Latinos than non‐Latinos, however. Language use, local ethnic context, national origin, and age were all significantly related to these identification choices. Conclusion. The format of “race” and “ethnicity” questions on surveys has significant implications for the identification patterns of Latinos.     

Social Work and Social Justice in Northern Ireland: Towards a New Occupational Space

Correspondence to: Dr John Pinkerton, School of Social Work, Queens University Belfast, 7 Lennoxvale, Belfast BT9 5BY, Northern Ireland. E-mail j.pinkerton{at}qub.ac.uk Summary This article considers the concept of social justice by referenceto the experience of social work in Northern Ireland duringthe past forty years of communal, paramilitary and state violence.It notes the contested nature of the concept and its chequeredhistory within the professional ideology of social work generallyand its absence as a significant explanatory and motivationalconcept for social workers in Northern Ireland to date. It arguesthat in the emerging post-conflict situation social work asa profession needs to operationalize a view of social justicethat acknowledges social and cultural diversity in order toredefine the profession itself and direct its relationship toboth the state and civil society.     

Neighbourhood Life,Social Capital and Perceptions of Safety in the Western Suburbs of Adelaide

In this paper we report on a South Australian study of perceptions of safety and aspects of neighbourhood life including social capital which involved the analysis of 2400 self‐completed questionnaires. A path analysis found that perceptions of safety were directly associated with gender, age, perceptions of neighbourhood pollution and neighbourhood trust, and indirectly associated with age, neighbourhood pollution and neighbourhood connections. We conclude with a discussion of the implications of the findings for public policy.     

The Distribution of Sums of Certain I.I.D. Pareto Variates

ABSTRACT

Though the Pareto distribution is important to actuaries and economists, an exact expression for the distribution of the sum of n i.i.d. Pareto variates has been difficult to obtain in general. This article considers Pareto random variables with common probability density function (pdf) f(x) = (α/β) (1 + x/β)^α+1 for x > 0, where α = 1,2,… and β > 0 is a scale parameter. To date, explicit expressions are known only for a few special cases: (i) α = 1 and n = 1,2,3; (ii) 0 < α < 1 and n = 1,2,…; and (iii) 1 < α < 2 and n = 1,2,…. New expressions are provided for the more general case where β > 0, and α and n are positive integers. Laplace transforms and generalized exponential integrals are used to derive these expressions, which involve integrals of real valued functions on the positive real line. An important attribute of these expressions is that the integrands involved are non oscillating.     

Last‐In First‐Out Oligopoly Dynamics

This paper extends the static analysis of oligopoly structure into an infinite‐horizon setting with sunk costs and demand uncertainty. The observation that exit rates decline with firm age motivates the assumption of last‐in first‐out dynamics: An entrant expects to produce no longer than any incumbent. This selects an essentially unique Markov‐perfect equilibrium. With mild restrictions on the demand shocks, sequences of thresholds describe firms' equilibrium entry and survival decisions. Bresnahan and Reiss' (1993) empirical analysis of oligopolists' entry and exit assumes that such thresholds govern the evolution of the number of competitors. Our analysis provides an infinite‐horizon game‐theoretic foundation for that structure.     

Business Angel Investment as an Informal Learning Process: Does Experience Matter?

This paper addresses the question of how the informal learning processes of angel investors shape the way in which they assess new investment opportunities. Previous research has suggested that angels learn from their previous investment activity. However, the measurement of investment experience as a function of years of investing and number of investments made does not take into account how, and to what extent, learning occurs and how it impacts investors’ decision-making. To address this deficiency, we suggest a dynamic model of informal learning which incorporates the informal learning typology developed by Schugurensky and extended by Bennett, as a conceptual framework to understand how learning experiences impact angel investment decisions. Based on interviews and verbal protocol analysis with 30 investors, we demonstrate how learning impacts learning processes and outcomes as angels assess an investment opportunity. The findings highlight the importance of supporting angel learning with support for angel groups and angel training programmes.     

Strategic Management of Operations in the Emergency Department

This study is based on the analysis of field data on the revenues and patient flows that we collected on all adult emergency department (ED) visits to a level‐1 trauma, tertiary referral center. Our objective was to provide researchers in operations a rich overview of the processes, resources, and metrics of financial and operations performance in the ED. We analyze how patients, physicians, hospitals/physician employer groups, and payers are party to the value created and financial workflow of the ED. A waterfall model for professional services revenue is developed that highlights the impacts of changes in processes, resources, scale, complexity, and mix of patients treated in the ED. We also discuss future implications of new compensation models and potential scenarios that will focus upon controlling costs while maximizing population health and patient satisfaction. These models will necessitate re‐engineering of operations in the ED from a strategic perspective. Four major thrusts for selecting the capacity portfolio in the ED operations to align the interests of all the stakeholders are recommended. New avenues for research are also identified.