Model Selection and Shrinkage: An Overview

This special issue is concerned with model selection and shrinkage estimators. This Introduction gives an overview of the papers published in this special issue.     

Methods to assess measurement error in questionnaires of sedentary behavior

Sedentary behavior has already been associated with mortality, cardiovascular disease, and cancer. Questionnaires are an affordable tool for measuring sedentary behavior in large epidemiological studies. Here, we introduce and evaluate two statistical methods for quantifying measurement error in questionnaires. Accurate estimates are needed for assessing questionnaire quality. The two methods would be applied to validation studies that measure a sedentary behavior by both questionnaire and accelerometer on multiple days. The first method fits a reduced model by assuming the accelerometer is without error, while the second method fits a more complete model that allows both measures to have error. Because accelerometers tend to be highly accurate, we show that ignoring the accelerometer's measurement error, can result in more accurate estimates of measurement error in some scenarios. In this article, we derive asymptotic approximations for the mean-squared error of the estimated parameters from both methods, evaluate their dependence on study design and behavior characteristics, and offer an R package so investigators can make an informed choice between the two methods. We demonstrate the difference between the two methods in a recent validation study comparing previous day recalls to an accelerometer-based ActivPal.     

丹麦劳动力市场模式分析

丹麦劳动力市场模式是近年来国际劳动力市场模式中非常成功的一种模式,日益受到国际社会的关注。“丹麦模式”的基本特征是将灵活化的劳动力市场、慷慨的福利制度与积极的劳动力市场政策有机结合在一起构成了一个“金三角”,成功地平衡了劳动力市场的灵活性与安全性。丹麦劳动力市场模式以其传统的价值理念、良好的社会合作机制和混合经济体制为基础。随着全球化时代社会经济条件的变化,丹麦劳动力市场模式也面临着严峻的挑战。     

The Contingent-Claims Approach to Investment Decisions*

This paper presents a contingent-claims approach to project valuation when capital expenditures are made sequentially over time. It focuses on an important facet of sequential investment projects that the firm can undertake—or pass up projects—as more information becomes available. The contingent-claims approach takes account of this important feature of firms' investment decision process, whereas the traditional capital budgeting procedure does not. Since the traditional method does not reflect the options nature of investment opportunities, it underestimates the value of sequential investment projects. As a result, a naive implementation of the traditional capital budgeting procedure could result in rejecting profitable projects. The extent of undervaluation associated with the traditional capital budgeting procedure is greater when the correlation between the random component of the future asset value and that of the required capital expenditure is smaller and/or when the growth rate of the required capital expenditure is higher.     

西方儿童虐待成因的发展生态模型理论研究述评

发展生态模型是西方儿童虐待成因研究的重要理论框架,但国内对此缺少系统性介绍。该理论认为,儿童虐待产生自互动个体与嵌套生态系统层面间的交互影响,它主要以生态系统理论为理论基础,并以“生态整合模型”和“生态交互模型”为代表性理论模型。该理论具有重要的方法论意义,它可促使研究者突破单因素变量研究的窠臼,并转向多因素共构视角去理解儿童虐待成因;同时,也为儿童虐待治理实践提供了多因素和多层次的系统干预视角。该理论的出现丰富了儿童虐待研究者的理论想象力,可为我国家庭、学校等场域的儿童虐待和儿童保护研究和干预提供启示。     

对现代苏南模式转型发展的思考

"十二五"时期,是江苏全面建成小康社会并向率先基本实现现代化迈进的关键时期,苏南地区更是要走在江苏的前列,争取早日实现现代化。苏南经济社会的又好又快发展与在实践中走出来的苏南模式是息息相关的。在国内外经济形势变化的情况下,现代苏南模式要继承苏南模式的核心价值,把握好转型发展、创新发展和开放发展的内涵,积极发展民营经济,加快发展传统文化产业,增强模式的内生动力,助力江苏早日实现现代化。     

Model selection in high-dimensional noisy data: a simulation study

In many practical applications, high-dimensional regression analyses have to take into account measurement error in the covariates. It is thus necessary to extend regularization methods, that can handle the situation where the number of covariates p largely exceed the sample size n, to the case in which covariates are also mismeasured. A variety of methods are available in this context, but many of them rely on knowledge about the measurement error and the structure of its covariance matrix. In this paper, we set the goal to compare some of these methods, focusing on situations relevant for practical applications. In particular, we will evaluate these methods in setups in which the measurement error distribution and dependence structure are not known and have to be estimated from data. Our focus is on variable selection, and the evaluation is based on extensive simulations.     

Generalized estimator of population mean by using conventional and non-conventional measures in the presence of measurement errors

In survey research, it is assumed that reported response by the individual is correct. However, given the issues of prestige bias, self-respect, respondent's reported data often produces estimated values which are highly deviated from the true values. This causes measurement error (ME) to be present in the sample estimates. In this article, the estimation of population mean in the presence of measurement error using information on a single auxiliary variable is studied. A generalized estimator of population mean is proposed. The class of estimators is obtained by using some conventional and non-conventional measures. Simulation and numerical study is also conducted to assess the performance of estimators in the presence and absence of measurement error.     

基于高维波动率网络模型的股票市场风险特征研究

波动率是金融风险管理研究的重要内容之一。本文基于复杂网络理论和数据挖掘技术提出股票市场的高维波动率网络模型。首先运用互信息度量不同股票价格波动之间的相关关系,其次对股票市场不同周期下的波动情况建立度的中心势、平均距离、幂律分布等网络拓扑指标,再次根据这些指标利用Prim算法构建出高维波动率网络模型,最后运用Newman-Girvan算法对股票价格波动率的相关性进行分层研究。高维波动率网络模型突破了传统波动率模型关于变量维数的限制,能够在依赖少量假设的基础上,挖掘出多个金融市场主体间的相互关系,反映金融市场的风险特征及网络拓扑性质。实证结果发现：与常用的Pearson相关系数法相比,在互信息框架下,股价波动的非线性相关关系得到了更好的度量;股票市场的整体波动性与个股波动率相关性变化趋势相反,市场处在高波动时期资产组合分散化效果较好;网络中存在少量度数大的关键节点和中心节点,风险通过这些节点可以迅速传递到整个市场;股票市场的运行具有明显的行业聚集现象;网络分层研究进一步直观的展现了风险在层与层之间的传递规律和与之对应的行业特征。高维波动率网络模型为挖掘股票市场的风险特征与管理金融风险提供了一个新的工具。     

金融周期、金融波动与中国经济增长——基于省际面板门槛模型的研究

本文应用面板门槛模型,研究了2005-2017年间我国31个省（市、自治区）金融波动对经济增长的影响。研究发现,随着金融周期所处阶段的变化,金融波动对经济增长会产生显著的非对称性双重门槛效应,主要体现为如下两点：首先,金融周期处于膨胀期、平稳期和萧条期时金融波动对经济增长会产生负向影响,但从影响系数值的大小来看,处于膨胀期时最大,是后两者的2倍之多,处于平稳期时最小且并不显著;其次,分区域的稳健性检验表明,金融发展水平高的区域双重门槛值出现得早,且两个门槛值间的区间要比金融发展水平低的区域宽28%。这些结论说明,经济增长对于金融波动的容忍弹性会随着金融周期所处的阶段而变化,金融发展水平的提高会放大经济增长对金融波动的容忍区间,但也会加速金融周期处于膨胀期时爆发金融危机的可能性,这使得当前我国存在着进一步发展金融水平和严控金融风险的矛盾,对此本文也提出了相应的政策建议。