食品安全规制能提高生产者福利吗？——基于不同规制强度的检验

食品安全规制涉及政府、生产者和消费者三方利益主体的博弈。已有文献主要关注政府规制对减少生产者违规概率、提升食品安全水平和消费者福利所产生的作用。本文从生产者福利视角考察企业参与食品安全规制是否存在“收益率溢价”效应，以此对中国食品安全规制的间接效果进行实证检验。首先采用倾向得分匹配模型考察食品安全规制对企业资产收益率的平均影响效应，然后采用广义倾向得分匹配模型和门槛模型进一步考察不同规制强度与企业资产收益率的非线性关系。研究表明，当前食品安全规制对参与规制企业产生了“收益率溢价”的间接效果,但随着规制强度的扩展，企业资产收益率呈现先上升后下降的“倒U型”变化，具有显著的双重门槛特征，当企业持有4项质量认证证书时为“最优规制强度”。最后结合当前中国实际，解释了上述结论产生的原因及政策含义。     

Does studying abroad enhance employability?

Over 200,000 European students study abroad under the Erasmus programme. It appears that studying abroad may impart skills which are helpful for professional careers after graduation. Approximately, 54% of European students report that participation in the Erasmus exchange programme helped them to obtain a first job; however, interestingly, those from Central and Eastern European countries report it much more often—in 73% of cases. The aim of this paper is to find out whether studying abroad enhances the employability of higher education graduates in Poland. Using the propensity score matching method and data from a nationwide tracer survey of Polish graduates, we find that Polish students who completed at least one semester of their studies abroad do not benefit in terms of a higher employment rate after graduation.     

Model-based control charts in phase 1 statistical process control

In this paper, a general method of constructing control charts for preliminary analysis of individual observations is presented, which is based on recursive score residuals. A simulation study shows that certain implementations of these charts are highly effective in detecting assignable causes.     

Are Venture Capitalists a Catalyst for Innovation?

In this paper we test two hypotheses concerning the presence of innovation in venture capital investments and the growth of innovative venture backed firms. To examine these hypotheses we considered sample of 37 Italian venture backed firms that went public on the Italian Stock Exchange between 1995 and 2004 and by a statistical matching procedure we picked 37 twin firms among the non‐venture backed IPOs for the same period. Our evidence shows that innovation is an important factor during the selection phase but once the investment is made, the company does not promote continued innovation and concentrates all efforts to improve other economic and managerial aspects.     

Modeling Conditional Yield Densities

Given the increasing interest in agricultural risk, many have sought improved methods to characterize conditional crop-yield densities. While most have postulated the Beta as a flexible alternative to the Normal, others have chosen nonparametric methods. Unfortunately, yield data tends not to be sufficiently abundant to invalidate many reasonable parametric models. This is problematic because conclusions from economic analyses, which require estimated conditional yield densities, tend not to be invariant to the modeling assumption. We propose a semiparametric estimator that, because of its theoretical properties and our simulation results, enables one to empirically proceed with a higher degree of confidence.     

On estimating the mean of the selected normal population under the LINEX loss function

Following Parsian and Farsipour (1999), we consider the problem of estimating the mean of the selected normal population, from two normal populations with unknown means and common known variance, under the LINEX loss function. Some admissibility results for a subclass of equivariant estimators are derived and a sufficient condition for the inadmissibility of an arbitrary equivariant estimator is provided. As a consequence, several of the estimators proposed by Parsian and Farsipour (1999) are shown to be inadmissible and better estimators are obtained. Received January 2001/Revised May 2002     

广东省现代物流的供需匹配研究

广东省现代物流正处于快速增长的阶段，如何协调物流供给与需求的矛盾，是现代物流发展过程中不可避免的问题。本文从物流的需求和供给的状况着手，分析了广东省现代物流存在供需不平衡问题的原因与表象，对匹配广东省现代物流的需求与供给提出了几条建议。     

Nonparametric efficiency analysis: A multivariate conditional quantile approach

This paper focuses on nonparametric efficiency analysis based on robust estimation of partial frontiers in a complete multivariate setup (multiple inputs and multiple outputs). It introduces α-quantile efficiency scores. A nonparametric estimator is proposed achieving strong consistency and asymptotic normality. Then if α increases to one as a function of the sample size we recover the properties of the FDH estimator. But our estimator is more robust to the perturbations in data, since it attains a finite gross-error sensitivity. Environmental variables can be introduced to evaluate efficiencies and a consistent estimator is proposed. Numerical examples illustrate the usefulness of the approach.     

Memory recall errors in retrospective surveys: A reverse record check study

This paper reports on a study to compare self-reports during an interview with staff who attended a University health centre in Turkey, with the records of visits to the same health centre over the previous 12 months. Design of the study reflects the effects of importance of the event, duration since the event, frequency of the occurrence of the event, measurement scale of the event, and bounded and unbounded recalling. In order to assess the extent of recall error, responses to retrospective questions on health centre visits are compared with administrative records. Statistical models are proposed for short and long term human memory recall error effects on responses.