Best monotone M‐estimators

The author shows how to find M‐estimators of location whose generating function is monotone and which are optimal or close to optimal. It is easy to identify a consistent sequence of estimators in this class. In addition, it contains simple and efficient approximations in cases where the likelihood function is difficult to obtain. In some neighbourhoods of the normal distribution, the loss of efficiency due to the approximation is quite small. Optimal monotone M‐estimators can also be determined in cases when the underlying distribution is known only up to a certain neighbourhood. The author considers the e‐contamination model and an extension thereof that allows the distributions to be arbitrary outside compact intervals. His results also have implications for distributions with monotone score functions. The author illustrates his methodology using Student and stable distributions.     

NONPARAMETRIC QUANTILE ESTIMATION FROM RECORD-BREAKING DATA

Sometimes, in industrial quality control experiments and destructive stress testing, only values smaller than all previous ones are observed. Here we consider nonparametric quantile estimation, both the ‘sample quantile function’ and kernel-type estimators, from such record-breaking data. For a single record-breaking sample, consistent estimation is not possible except in the extreme tails of the distribution. Hence replication is required, and for m. such independent record-breaking samples the quantile estimators are shown to be strongly consistent and asymptotically normal as m-→∞. Also, for small m, the mean-squared errors, biases and smoothing parameters (for the smoothed estimators) are investigated through computer simulations.     

AN EXACT CONDITIONAL TEST FOR COVARIANCE SELECTION MODELS

An exact conditional test is developed for testing the absence of an edge in a graphical covariance selection model and is shown to be equivalent to a test based on the partial correlation coefficient. An example is given.     

Life-threatening disability in adolescence: Adjusting to a limited future

This paper describes a medical social worker's efforts over one and a half years to help a client adjust to a neurological disorder. Prior to social work services, the young woman had never discussed her disability, which began in adolescence, with anyone outside the family, and communication within the family was seriously compromised by their perception of disability as a stigma. Lacking the opportunity to mourn the loss of her physical abilities, she became isolated and depressed, and acted out aggressive thoughts and fantasies within the family system. Social work intervention helped the client to re-work the original trauma of diagnosis, which led to the development of a healthier defensive structure and new coping mechanisms.     

Enclaves, neighbourhood effects and employment outcomes: Ethnic minorities in England and Wales

Ethnic minorities in England and Wales are spatially concentrated in relatively-deprived urban areas. Both geographic clustering and the economic characteristics of ethnically-concentrated neighbourhoods can impact upon the opportunities and constraints facing residents of such areas. This paper explores the relationship between the existence of enclaves and the employment prospects of ethnic minorities in England and Wales. It is shown that there is considerable spatial variation in employment outcomes. There is a lower incidence of self-employment in more ethnically-concentrated urban areas, which contradicts the view of ethnic entrepreneurship as an enclave phenomenon. Unemployment rates are also higher for minorities living in more concentrated areas. Enclaves in England and Wales do not appear to offer many economic benefits to minority individuals. Received: 31 December 1999/Accepted: 27 November 2000     

实现可持续发展的障碍:欧洲和加拿大对高等教育的认识

“可持续发展”这个说法本身具有多种含义。在高等教育中 ,它被用来促进现有的政治、经济和官僚制度的延续。不过 ,它也被用于描述一种使高等教育机构对社会和环境负起更多责任的运动。后者正是本文所要讨论的问题。大学和其他高等教育机构应该把它们所讲授的内容付诸实践———从有关伦理道德和社会行为的概念到对平等和性别的看法。在大学需要注意的问题中 ,特别应该强调可持续发展问题。因为可持续发展不仅包含了上述伦理道德和社会行为方面的问题 ,而且要求优良的管理 ,并鼓励优良的学术实践。实现可持续发展的道路并非一帆风顺 ,而需要…     

EFFICIENT USER CHARGES IN A RENT-SEEKING MODEL

This paper examines efficient user charges on governmentally provided facilities in the presence of rent seeking. We find that the efficient user charge depends upon the relative slopes of the demand curve for the use of the facility and the corresponding marginal cost curve, as well as the level of rent seeking over the revenue raised. Except for a special case, the efficient user charge is found to differ from the charge indicated by the intersection of demand and marginal cost curves. Examples show that actual user charges on government facilities are often set at inefficient levels.