A General Class of Estimators for the Linear Regression Model Affected by Collinearity and Outliers

In this article, a general class of estimators for the linear regression model affected by outliers and collinearity is introduced and studied in some detail. This class of estimators combines the theory of light, maximum entropy, and robust regression techniques. Our theoretical findings are illustrated through a Monte Carlo simulation study.     

A note on the changing relationship between fertility and female employment rates in developed countries

In this paper we look at a panel of OECD aggregate fertility and labor market data between 1970 and 1995 and we report some striking recent developments. Total Fertility Rates (TFR) were falling and Female Participation Rates (FPR) were increasing, conforming to a well known long-run trend. Along the cross-sectional dimension, the correlation between TFR and FPR was negative and significant during the 1970's and up to the early 1980's. This seemed consistent with secular comovements. However, by the late 1980's the correlation had become positive and equally significant. We discuss our findings within the framework of standard neoclassical models of fertility and labor supply adapted to macro data, as in Butz and Ward (1979). Received: 14 April 2000/Accepted: 29 December 2000 All correspondence to Pedro Mira. Namkee Ahn is grateful for financial support received from the Bank of Spain and from Spain's Ministerio de Educación y Cultura, grant SEC97-1249. We benefited from comments by two anonymous referees and by seminar participants at FEDEA, CEMFI and ESPE-98. All remaining errors are our own. Responsible editor: John F. Ermisch.     

Clustering to reduce regional heterogeneity: A spanish case-study

Statistical methods of dimension reduction and classification are used to obtain homogeneous local-area clustering with regard to the most relevant demographic parameters. The dimension reduction is conducted in two stages using Principal Component Analysis and a modified k-mean procedure is proposed to determine the final clusters. This clustering will be useful in future demographic studies at a local level, in particular to obtain forecasts of demographic rates and population projections. The region of Castile and León in Spain is used to illustrate the method. A Poisson model is used to explore the advantages of the new clustering over the more conventional classification based on provinces.     

The Impact of Overeducation on Wages of Recent Economic Sciences Graduates

Social Indicators Research - United Nations Development Program presented the Human Development Index for ranking the countries with regard to three dimensions, namely being knowledgeable, a long...     

Modeling the impact of social discrimination on the physical and mental health of Portuguese gay,lesbian and bisexual people

Background: Despite growing acceptance of same-sex sexuality in Portugal, identity development of lesbian, gay and bisexual (LGB) individuals is still restricted by negative societal attitudes, which maintain the experience of stigmatization and discrimination. The purpose of this study is to document the frequency of discriminatory events experienced by sexual minorities and their association with indicators of physical and mental health in Portugal. Methods: A total of 610 LGB participants completed an online survey (mean age?=?34.48, SD?=?11.54). Most participants were single and self-identified as gay (73.8%). The survey included five categories of survey items: demographic information, social support, physical health, mental health, and discrimination experiences. Results: Physical and mental health results revealed that bisexual people were more likely to report higher levels of psychological distress than gay men. Overall, between one-fifth and one-fourth of the participants in this sample frequently felt the need to hide their sexual orientation to prevent discrimination experiences across the different settings. Regarding actual discrimination experiences, close to 20% reported having suffered from verbal abuse, followed by close to 10% who suffered from written threats, harassment, and physical threats. A hierarchical multiple regression analysis was performed to assess the effects of anticipated and actual discrimination on mental health. Possible confounding variables were added in the first block – age, sexual orientation, being in a relationship, body mass index, and HIV status. Anticipated and actual discrimination experiences were added in the second block. The first block of the analysis explained 6% of the overall variance, while the second block – discrimination experiences – explained an additional 17%. Conclusion: Portuguese culture and stigma/discrimination create discriminatory experiences which impact LGB people's health. Unless policies are changed to allow for the acceptance of LGB people, they will continue to experience violence and discrimination as a result of homophobia.     

Monitoring correlation change in a sequence of random variables

We propose a monitoring procedure to test for the constancy of the correlation coefficient of a sequence of random variables. The idea of the method is that a historical sample is available and the goal is to monitor for changes in the correlation as new data become available. We introduce a detector which is based on the first hitting time of a CUSUM-type statistic over a suitably constructed threshold function. We derive the asymptotic distribution of the detector and show that the procedure detects a change with probability approaching unity as the length of the historical period increases. The method is illustrated by Monte Carlo experiments and the analysis of a real application with the log-returns of the Standard & Poor's 500 (S&P 500) and IBM stock assets.     

PROMETHEE IV through kernel density estimation

ABSTRACT

This paper presents a new version of PROMETHEE IV, which considers the empirical distribution of the criteria through kernel density estimation to evaluate alternatives. The developed method has the ability to treat criteria according to their distribution. The classic PROMETHEE IV can produce divergent integrals, and this could be the cause for its insufficient exploration in literature. The proposed method overcomes this situation since large values have little weight compared to values near the mean.     

Postural assessment of school children: an input for the design of furniture

During the last decades of the previous century, school desks with a tilt top have disappeared. The chairs have been designed for sitting upright, with the hip, knees and ankles all at right angles. However, the erect posture cannot be maintained for more than one or two minutes, after which it will result in fatigue, discomfort or poor posture. The main aim of project is to identify the type of furniture that most effectively contribute to adequate neck and back postures of the school children, by carrying out a postural analysis of a sample of school pupils when using three different types of furniture. The postures adopted by school pupils were monitored by video during several activities, such as reading, writing and painting tasks, copying from a blackboard and listening the teacher. Additionally, the characteristics of the adopted postures were assessed by registering the head tilt, flexion of the neck, trunk and hips position. All these aspects were classified and the results were recorded for future analysis. The obtained results seem to point out that the use of a school desk with a tilted table surface resulted in a reduction in trunk and neck flexion, preserving the natural lordosis in the lumbar and cervical regions. Accordingly, it can be concluded that there are alternatives to consider in the furniture design in order to eliminate tensions and, consequently, to improve children's wellbeing.