A Non‐Parametric Estimator of the Spectral Density of a Continuous‐Time Gaussian Process Observed at Random Times

Abstract. In numerous applications data are observed at random times and an estimated graph of the spectral density may be relevant for characterizing and explaining phenomena. By using a wavelet analysis, one derives a non‐parametric estimator of the spectral density of a Gaussian process with stationary increments (or a stationary Gaussian process) from the observation of one path at random discrete times. For every positive frequency, this estimator is proved to satisfy a central limit theorem with a convergence rate depending on the roughness of the process and the moment of random durations between successive observations. In the case of stationary Gaussian processes, one can compare this estimator with estimators based on the empirical periodogram. Both estimators reach the same optimal rate of convergence, but the estimator based on wavelet analysis converges for a different class of random times. Simulation examples and an application to biological data are also provided.     

On Variance Components in Semiparametric Mixed Models for Longitudinal Data

Abstract. First, to test the existence of random effects in semiparametric mixed models (SMMs) under only moment conditions on random effects and errors, we propose a very simple and easily implemented non‐parametric test based on a difference between two estimators of the error variance. One test is consistent only under the null and the other can be so under both the null and alternatives. Instead of erroneously solving the non‐standard two‐sided testing problem, as in most papers in the literature, we solve it correctly and prove that the asymptotic distribution of our test statistic is standard normal. This avoids Monte Carlo approximations to obtain p ‐values, as is needed for many existing methods, and the test can detect local alternatives approaching the null at rates up to root n. Second, as the higher moments of the error are necessarily estimated because the standardizing constant involves these quantities, we propose a general method to conveniently estimate any moments of the error. Finally, a simulation study and a real data analysis are conducted to investigate the properties of our procedures.     

Variability explained by covariates in linear mixed‐effect models for longitudinal data

Variability explained by covariates or explained variance is a well‐known concept in assessing the importance of covariates for dependent outcomes. In this paper we study R² statistics of explained variance pertinent to longitudinal data under linear mixed‐effect models, where the R² statistics are computed at two different levels to measure, respectively, within‐ and between‐subject variabilities explained by the covariates. By deriving the limits of R² statistics, we find that the interpretation of explained variance for the existing R² statistics is clear only in the case where the covariance matrix of the outcome vector is compound symmetric. Two new R² statistics are proposed to address the effect of time‐dependent covariate means. In the general case where the outcome covariance matrix is not compound symmetric, we introduce the concept of compound symmetry projection and use it to define level‐one and level‐two R² statistics. Numerical results are provided to support the theoretical findings and demonstrate the performance of the R² statistics. The Canadian Journal of Statistics 38: 352–368; 2010 © 2010 Statistical Society of Canada     

考虑溢出效应的互补品企业间广告决策模型研究

具有需求信息优势的企业常常将广告投入作为市场需求信号,有选择地向其互补品生产企业传递需求信息,以刺激其增加广告投入,通过溢出效应获取更大收益。针对这一问题,本文建立了考虑溢出效应的互补品企业间广告决策的信号博弈模型,得到了分离均衡和混同均衡的存在条件,分析了均衡状态下企业的最优广告决策和收益,讨论了企业的广告策略选择。结果表明,分离均衡下,具有信息优势的制造商无法利用广告投入信号刺激其互补品制造商增加广告投入。混同均衡下,只有当市场需求为低时,具有信息优势的制造商能够利用广告投入信号,刺激其互补品制造商增加广告投入,通过溢出效应获得更大收益。最后,通过一个数值算例验证了有关结论的有效性。     

参数不确定性对投资者最优资产组合的影响：基于中国的实证

现代金融学主要目标是给出具有科学依据的投资建议。这一任务对于投资期限较短的投资者已完成,但对面临时变性投资机会的长期投资者,金融学家还不能给出高精度的投资建议。文章考虑投资者自身预测力存在估计误差的感知风险(参数不确定性)对投资者最优资产组合选择问题的影响。运用我国资本市场数据的实证研究表明:忽略参数不确定性对资产组合选择问题的影响将会误导投资者配置过多的风险资产。     

基于委托-代理理论的团队运作条件模型分析

分析了团队工作的协同效应与"搭便车"效应。建立了员工独立工作与团队工作的委托-代理模型。通过对比不同工作方式下委托人的收益,得出结论:团队合作是否优于个人单独工作取决于合作的协同系数、外生随机变量的方差、成员的风险规避度及努力成本系数;只有工作性质与人员特征相互匹配,使得4种因素满足一定条件时,团队运作才是有利的,否则独立工作是最佳选择。     

Asymptotic Properties for a Class of Partially Identified Models

We propose inference procedures for partially identified population features for which the population identification region can be written as a transformation of the Aumann expectation of a properly defined set valued random variable (SVRV). An SVRV is a mapping that associates a set (rather than a real number) with each element of the sample space. Examples of population features in this class include interval‐identified scalar parameters, best linear predictors with interval outcome data, and parameters of semiparametric binary models with interval regressor data. We extend the analogy principle to SVRVs and show that the sample analog estimator of the population identification region is given by a transformation of a Minkowski average of SVRVs. Using the results of the mathematics literature on SVRVs, we show that this estimator converges in probability to the population identification region with respect to the Hausdorff distance. We then show that the Hausdorff distance and the directed Hausdorff distance between the population identification region and the estimator, when properly normalized by , converge in distribution to functions of a Gaussian process whose covariance kernel depends on parameters of the population identification region. We provide consistent bootstrap procedures to approximate these limiting distributions. Using similar arguments as those applied for vector valued random variables, we develop a methodology to test assumptions about the true identification region and its subsets. We show that these results can be used to construct a confidence collection and a directed confidence collection. Those are (respectively) collection of sets that, when specified as a null hypothesis for the true value (a subset of values) of the population identification region, cannot be rejected by our tests.     

Effects of Risk Representation and Scope on Willingness to Pay for Reduced Risks: Evidence from Tokyo Bay, Japan

When applying the contingent valuation method (CVM) in risk reduction studies, some studies report that willingness to pay (WTP) is insensitive to the magnitude of risk reduction while other studies do not. On the other hand, social-psychological research has shown that the affect heuristic biases judgments on probability, relative frequency, and risk. This article examines both magnitude (or scope) effect and affect heuristic (or representation) effect on WTP for risk reduction measures against tsunamis by introducing two experimental (i.e., absolute and relative) systems with four different representations to evaluate public behaviors in two different scenarios of risk reduction. Two common denominators (100 and 10,000) are introduced into absolute risk reduction representation (i.e., "of every 100 persons, from present 2 deaths to 1") to form different formats (i.e., "of every 10,000 persons from 200 to 100," and "of every 100,000 persons from 2,000 deaths to 1,000"). There is little evidence that WTP estimates are sufficiently sensitive to the magnitude of risk reduction, but relative risk reduction representations may be better than the absolute one given in CVM mail surveys when the risk is small. There is a statistically insignificant effect of risk reduction representations on respondent frequency, but mixed effects on the monetary values of WTP at the level of 0.05. The representation effect of absolute risk reduction on the WTP value varies with the common denominator. The larger the common denominator, the less the WTP to reduce the risk of tsunamis, and the significance probability is improved to less than the level of 0.05 when the common denominator becomes large enough. The findings suggest that improved methods are required for estimating the rates of tradeoff between fatality risk and other goods among consumers.     

The effect of alliance experience and intellectual capital on the value creation of international strategic alliances

This paper investigates the effects of intellectual capital (IC), alliance experience and their interaction on the value creation of international strategic alliances (ISAs). Based on a sample of ISAs formed by US firms, we find that firms with a higher level of IC receive greater announcement-period wealth gains. In addition, the empirical results suggest experience positively enhances the wealth effect of ISAs. Finally, we find a significant positive interaction effect between experience and IC on the wealth creation of ISAs. The results demonstrate the importance of considering the joint effects of IC and experience in assessing the value creation of ISAs.     

流动性资产定价理论与实证研究

由于交易成本、市场摩擦等因素的影响,资产价格偏离标准资产定价理论的预期,产生了流动性溢价。非流动性产生的来源、机理、性质引起学术界持续的兴趣,尤其是非流动性对最优消费和投资策略,资产价格和收益,以及风险溢价的影响成为资产定价领域里最具有挑战性的课题之一。本文从理论和实证两个方面对探讨流动性与资产价格之间关系的文献进行了简要回顾。