Stable Asymptotics for M‐estimators

We review some first‐order and higher‐order asymptotic techniques for M‐estimators, and we study their stability in the presence of data contaminations. We show that the estimating function (ψ) and its derivative with respect to the parameter play a central role. We discuss in detail the first‐order Gaussian density approximation, saddlepoint density approximation, saddlepoint test, tail area approximation via the Lugannani–Rice formula and empirical saddlepoint density approximation (a technique related to the empirical likelihood method). For all these asymptotics, we show that a bounded ψ (in the Euclidean norm) and a bounded (e.g. in the Frobenius norm) yield stable inference in the presence of data contamination. We motivate and illustrate our findings by theoretical and numerical examples about the benchmark case of one‐dimensional location model.     

农户参与农业废弃物资源化利用的意愿及其影响因素分析——基于黑、鲁、豫、川4省684户农户的调查数据

农业废弃物资源化利用是防治农业面源污染、改善农业生产环境的有效途径;同时,也是改善农村人居环境,推动生态宜居美丽乡村建设的重要内容。基于黑龙江、山东、河南、四川4省684个样本农户数据,运用多元排序Probit模型分析了农户农业废弃物资源化利用参与意愿及其影响因素,并通过控制相关变量进行了稳健性检验。结果表明,政府监管并不能提高农户参与农业废弃物资源化利用的意愿,而前景预期、政策了解度、农业废弃物资源化补贴、设立固定回收点或与回收企业合作、合作社参与等因素更能提高农户的参与意愿。为此,可以采取发挥非经济预期的作用、构建财政补贴机制、健全农业废弃物资源化回收利用机制、利用合作社平台等措施激发农户参与农业废弃物资源化利用的关键行为动机,提高农户参与农业废弃物资源化利用的意愿,推动农业绿色发展及乡村生态振兴。     

一种基于时间轴小波变换的鲁棒性水印算法研究

针对视频水印常见的攻击和视频压缩攻击,文章提出了一种时间轴小波域的视频水印算法。该算法选取每个场景中连续的8帧视频嵌入水印,让8帧视频图像进行3重时间轴小波变换得到一个低频帧,通过自适应的方式将水印嵌入低频帧的DCT中低频系数中,从而有效地保证了水印的抗攻击性。实验结果表明,该视频水印系统在不可见的同时具有很强的鲁棒性和安全性。     

资本结构影响因素稳健性检验

关于资本结构影响因素的理论和实证研究存在很多相互矛盾的结论,人们通常把这个问题归咎于外部因素的影响,而没有怀疑资本结构理论自身的稳健性;本研究发现相互矛盾的研究结果并非由外部因素引起,而是由于资本结构理论本身缺乏较强的稳健性。因此,传统的资本结构理论并不适用于指导我国企业的融资实践,应该从企业外部,而不是过去理论强调的“从企业内部”去寻找影响资本结构的因素。     

ON THE CONSISTENCY OF REGRESSION‐BASED MONTE CARLO METHODS FOR PRICING BERMUDAN OPTIONS IN CASE OF ESTIMATED FINANCIAL MODELS

In many applications of regression‐based Monte Carlo methods for pricing, American options in discrete time parameters of the underlying financial model have to be estimated from observed data. In this paper suitably defined nonparametric regression‐based Monte Carlo methods are applied to paths of financial models where the parameters converge toward true values of the parameters. For various Black–Scholes, GARCH, and Levy models it is shown that in this case the price estimated from the approximate model converges to the true price.     

Model misspecification,Bayesian versus credibility estimation,and Gibbs posteriors

ABSTRACT

In the context of predicting future claims, a fully Bayesian analysis – one that specifies a statistical model, prior distribution, and updates using Bayes's formula – is often viewed as the gold-standard, while Bühlmann's credibility estimator serves as a simple approximation. But those desirable properties that give the Bayesian solution its elevated status depend critically on the posited model being correctly specified. Here we investigate the asymptotic behavior of Bayesian posterior distributions under a misspecified model, and our conclusion is that misspecification bias generally has damaging effects that can lead to inaccurate inference and prediction. The credibility estimator, on the other hand, is not sensitive at all to model misspecification, giving it an advantage over the Bayesian solution in those practically relevant cases where the model is uncertain. This begs the question: does robustness to model misspecification require that we abandon uncertainty quantification based on a posterior distribution? Our answer to this question is No, and we offer an alternative Gibbs posterior construction. Furthermore, we argue that this Gibbs perspective provides a new characterization of Bühlmann's credibility estimator.     

财政投入和金融支持对农民农业增收贡献的比较

基于2000～2013年省级面板数据,运用固定效应模型和分位数回归模型考察了财政投入和金融支持对提升农民农业收入的影响,并采用因素分解法比较两者对农民农业增收的贡献大小,继而通过两步固定效应回归、分组回归和替换变量回归三种方式检验结果的稳健性,均得出一致结果,即财政投入和金融支持均促进农业增收,其中财政投入贡献更大,此外大规模的土地投入和完善的基础设施建设也有利于农业收入提高.     

Benchmark Invariancy,Seasonality and APM-Free Portfolio Performance Measures

The Jobson-Korkie (1981) Z score and the positive period weighting (PPW) score of Grinblatt and Titman (1989) are applied to various benchmarks of market and mimicking portfolios to study the benchmark invariancy problem. Significantly different portfolio performance inferences are found for a sample of 146 equity mutual funds depending on the mean-variance efficiency of the portfolio benchmarks (mimicking portfolios versus market indices). Portfolio performance inferences are affected significantly by the number of factors, nonsynchronous trading adjustment, and the sizes of the firms used for factor extraction. The returns of the portfolio benchmarks exhibit significant monthly seasonalities, which, in turn, significantly influence mutual fund performance inferences.     

Chi-Square Tests Under Models Close to the Normal Distribution

Many test statistics follow a χ² distribution because a normal model is assumed as underlying distribution. In this paper we obtain good analytic approximations for the p-value and the critical value of χ² tests when the underlying distribution is close but different from the normal model. With these approximations we study the robustness of validity of χ² tests     

一种基于均值量化的小波域自同步数字音频水印算法

提出了一种基于均值量化的小波域自同步数字音频水印算法。该算法是一种盲检测算法,检测时不需要原始音频信号。算法引入了系数均值量化的思想,音频信号进行小波分解后,对其中的低频系数进行均值量化,嵌入水印;并且引入了嵌入同步信号的思想,利用同步信号来定位水印的嵌入位置,以抵抗平移、裁剪等攻击。实验结果表明该算法具有较强的鲁棒性和抗攻击性。