Performance of empirical Bayes estimators of random coefficients in multilevel analysis: Some results for the random intercept-only model

For a multilevel model with two levels and only a random intercept, the quality of different estimators of the random intercept is examined. Analytical results are given for the marginal model interpretation where negative estimates of the variance components are allowed for. Except for four or five level-2 units, the Empirical Bayes Estimator (EBE) has a lower average Bayes risk than the Ordinary Least Squares Estimator (OLSE). The EBEs based on restricted maximum likelihood (REML) estimators of the variance components have a lower Bayes risk than the EBEs based on maximum likelihood (ML) estimators. For the hierarchical model interpretation, where estimates of the variance components are restricted being positive, Monte Carlo simulations were done. In this case the EBE has a lower average Bayes risk than the OLSE, also for four or five level-2 units. For large numbers of level-1 (30) or level-2 units (100), the performances of REML-based and ML-based EBEs are comparable. For small numbers of level-1 (10) and level-2 units (25), the REML-based EBEs have a lower Bayes risk than ML-based EBEs only for high intraclass correlations (0.5).     

Robustness issues in multilevel regression analysis

A multilevel problem concerns a population with a hierarchical structure. A sample from such a population can be described as a multistage sample. First, a sample of higher level units is drawn (e.g. schools or organizations), and next a sample of the sub‐units from the available units (e.g. pupils in schools or employees in organizations). In such samples, the individual observations are in general not completely independent. Multilevel analysis software accounts for this dependence and in recent years these programs have been widely accepted. Two problems that occur in the practice of multilevel modeling will be discussed. The first problem is the choice of the sample sizes at the different levels. What are sufficient sample sizes for accurate estimation? The second problem is the normality assumption of the level‐2 error distribution. When one wants to conduct tests of significance, the errors need to be normally distributed. What happens when this is not the case? In this paper, simulation studies are used to answer both questions. With respect to the first question, the results show that a small sample size at level two (meaning a sample of 50 or less) leads to biased estimates of the second‐level standard errors. The answer to the second question is that only the standard errors for the random effects at the second level are highly inaccurate if the distributional assumptions concerning the level‐2 errors are not fulfilled. Robust standard errors turn out to be more reliable than the asymptotic standard errors based on maximum likelihood.     

Energy,knowledge and economic growth

It is argued that the explosive growth experienced in much of the World since the middle of the 19th Century is due to the exploitation and use of fossil fuels which, in turn, was made possible by capital good innovations that enabled this source of energy to be used effectively. Economic growth is viewed as the outcome autocatalytic co-evolution of energy use and the application of new knowledge associated with energy use. It is argued that models of economic growth should be built from innovation diffusion processes, unfolding in history, rather than from a timeless aggregate production function. A simple ‘evolutionary macroeconomic’ model of economic growth is developed and tested using almost two centuries of British data. The empirical findings strongly support the hypothesis that growth has been due to the presence of a ‘super-radical innovation diffusion process’ following the industrial deployment of fossil fuels on a large scale in the 19th Century. Also, the evidence suggests that large and sustained movements in energy prices have had a very significant long term role to play.     

Heterogeneity and exchange: Safe-conducts in Medieval Spain

During a time when religious animosities were reaching their peak in Medieval Europe leading up to the violent crusades, Christians, Jews, and Muslims residing in close proximity in Medieval Spain experienced a period of relative peace, prosperity, and cultural exchange. This historical episode, referred to as La Convivencia, or the coexistence, is a puzzle to many period historians. This paper argues that this anomalistic period arose due to the emergence of commerce, which generated cooperation and mitigated conflict among these heterogeneous groups, à la the Doux-Commerce Thesis of the Scottish Enlightenment. Commercial exchange between Christians, Jews, and Muslims was established through the use of safe-conducts, a promise of protection sold to foreign merchants. This paper details the operation of safe-conducts and the civilizing role that commerce played among Christians, Jews, and Muslims in Medieval Spain.     

Worldwide business trends create new leverage for voluntary benefits

The recent growth of interest in voluntary benefits has coincided with a decline in resources available to administer benefit programs. Fortunately, technology offers employers a solution to this resources dilemma in the form of portals, which allow employers to provide choice and access to voluntary benefits without concerns about increasing the workload for the benefits staff and without causing confusion among employees.     

Outcomes from use of an evidence-based practice guideline

The aim of evidence-based guidelines is primarily to improve patient outcomes without adding to the existing cost of care because both payers and policymakers want to identify health care costs that do not result in benefit to the patient. The purpose of the reported project was to generate a practice guideline for the treatment of uncomplicated acute cystitis in a female population, to determine the extent to which the guideline would be used by providers and to measure the cost and quality of outcomes from its use. A retrospective chart review was used to gather pre-guideline practice and cost data. Measurements included the type, frequency, and duration of antibiotic therapy and the use of urine cultures and both complications and routine followup visits. The implementation of an outpatient practice guideline resulted in a significant change in antibiotic prescribing and a trend toward a change in ordering cultures and clinic followup. There was also a significant decrease in treatment costs.     

江西大型企业资本运作模式的现状及其改进对策研究

资本运作是一种有效配置资源、实现企业资本增殖的活动,其核心是产权制度创新。本文对江西大型企业资本运作模式的现状进行了分析,进而提出了一系列的合理的改进对策,以期提高起运作绩效。     

多主体投资对经济增长贡献的回归分析

在市场经济条件下,多种资本的联合、重组和流动是促进经济发展的重要手段之一。本文根据道格拉斯生产函数、以改革开放近20年来的国有投资、集体投资和个体投资数据为样本构造了多主体投资生产函数,并进行多主体投资对经济增长的回归分析。     

Preferences in the Future

Environmental economics has been much occupied with the discount rate, which is the value of future costs and benefits relative to present costsor benefits. But at least as important is the question of whatshould be discounted, that is, what the value of those future environmentalbenefits is to future generations. This paper analyzes the role for futurepreferences and discusses the state of knowledge. I argue that theappropriate discount rate is the market one, and that the real problemis determining future willingness-to-pay. This approach makes clearerthe connection between discounting and the valuation debate.This paper focuses on two features that have been prominent in that debate:existence value and reference dependence. I argue that thereis a vital connection between the two constructs and that this link yieldsimportant implications for future willingness-to-pay.