Uniqueness of estimation and identifiability in mixture models

Further properties of the nonparametric maximum-likelihood estimator of a mixing distribution are obtained by exploiting the properties of totally positive kernels. Sufficient conditions for uniqueness of the estimator are given. This result is more general, and the proof is substantially simpler, than given previously. When the component density has support on N points, it is shown that all identifiable mixing distributions have support on no more than N/2 points. Identifiable mixtures are shown to lie on the boundary of the mixture model space. The maximum-likelihood estimate is shown to be unique if the vector of observations lies outside this space.     

The impact of positivity and transparency on trust in leaders and their perceived effectiveness

A critical challenge facing today's organizational leaders is gaining their followers' trust and having them view leaders as effective in addressing turmoil and change. Using a downsizing scenario as the context, this field experiment examined how a leader's positivity and transparency impacted followers' perceived trust, defined in terms of willingness to be vulnerable, and effectiveness of their leader. To test the hypotheses, 304 participants were randomly assigned to one of the four conditions of high (low) leader positivity × high (low) leader transparency. Results of our mixed methods study indicated both the leader's level of positivity and transparency impacted followers' perceived trust and evaluations of leader effectiveness. Besides limitations and suggestions for future research, we conclude with the practical implications that positive, transparent leaders may have on building trust and perceived effectiveness among their followers.     

Overcoming Barriers to Homeless Delivery Services: A Community Response

Homelessness is one of the most pressing social problems today. The.lnstitute of Medicine defines the problem as a failure in the support systems created to prevent the problem and a tighter housing market. The assumption is that the support system should help to prevent the occurrence of homelessness. The Eastern Fairfield County area peiformed a study to look at the relationship between those services serving people who are homeless and near homeless to determine the availability, accessibility, and adequacy of services for homeless people. The study identified several barriers in the service delivery system. A strategy was then developed to address these barriers. This paper shows how a research process can facilitate a community response to a social problem. The paper presents the steps that were taken so other communities may replicate the process.     

Estimation of the sum of differences distribution

Consider the distribution of Z_i d_iwhere the d.d_i?s are 1=1 lldifferences independently, identically and symmetrically distributed with mean zero. The problem is to determine properties of the sdd given the distribution of the d._i?fs and the sample size n. The standardized moments as a function of the moments of the d._i!s are developed. A variance reduction technique for estimating the quantiles of the sdd using Monte Carlo methods is developed based on using the randomization sample consisting of the 2ⁿ values of Z _i+d. rather than the single observation i=l lZ d. corresponding to each sample d_id_n. The randomization sample is shown to produce unbiased and consistent estimators.     

Public good theories of the non-profit sector: Weisbrod revisited

Burton Weisbrod's 1975 article, Toward a theory of the voluntary non-profit sector in a three-sector economy, models non-profit organisations as suppliers of public goods which are undersupplied by government to heterogeneous populations. This article examines the implications, extensions and empirical tests of the Weisbrod theory. It also examines the theories of pure and impure altruism, the heterogeneity hypothesis, and the various ‘publicness’ indexes of non-profit output. The commonalities between the public good model and the trustworthiness model of non-profit organisations are also explored. He is also a Research Associate of the Mandel Center for Nonprofit Organizations at Case Western Reserve University.     

AN EXCLUSIVE REGRESSORS BINARY MIXTURE MODEL WITH AN APPLICATION TO LABOUR SUPPLY

This paper suggests a new type of mixture regression model, in which each mixture component is explained by its own regressors. Thus, the dependent variable can be driven by one of several unobservable explanatory mechanisms, each of which has its own distinct variables. An extension of the simulated annealing algorithm is introduced to fit this general mixture model. The paper also suggests a new technique for estimating the covariance matrix of estimators in a mixture model. Finally, empirical studies of a labour supply example show that our proposed model can perform much better than conventional logistic or mixture models.     

The Rapid Rise of Supermarkets?

A series of articles, many of them published in this journal, have charted the rapid spread of supermarkets in developing and middle‐income countries and forecast its continuation. In this article, the level of supermarket penetration (share of the retail food market) is modelled quantitatively on a cross‐section of 42 countries for which data could be obtained, representing all stages of development. GDP per capita, income distribution, urbanisation, female labour force participation and openness to inward foreign investment are all significant explanators. Projections to 2015 suggest significant but not explosive further penetration; increased openness and GDP growth are the most significant factors.     

Media labeling versus the US disability community identity: a study of shifting cultural language

This study examines disability terminology to explore how the news media frame cultural representations of the disability community. More specifically, the paper examines the impact of the Americans with Disabilities Act on journalist's language choices about disability topics. A content analysis of news stories using disability terms in The Washington Post and The New York Times during the past decade was conducted. The paper illustrates that disability community identity continues to be formed, transformed and maintained through news media presentations of disability terminology. The paper argues that the US Disability Rights Movement had some success during the 1990s in putting forth language that advances its aims, though the study also suggests that some journalists continue to use terms that perpetuate limiting, narrow stereotypes about people with disabilities.     

Network Parenting in International Service Development

This paper explores theoretical and practical aspects (i.e. resources allocated, activities undertaken, actors/decisions involved) of corporate 'parenting' in the development of international service networks. A review of the relevant corporate strategy, supply-chain, networks and services management literature underpins a preliminary content (capability; market orientation) and process (top-down; bottom-up) typology of network parenting. This provides the structure for discussion of two telecommunications-sector case studies. Analysis of the data acknowledges the influence of generic network mechanisms (e.g. weak and strong social ties) but the parenting typology also highlights other mechanisms, the effectiveness of which appears contingent on specific parenting roles. The paper details these roles (labelled: governing; training; curating; facilitating) and makes some preliminary comments on the role trajectories (e.g. governing ↔ training) observed. The paper concludes with a discussion of possible directions for future work.