Zero Correlation,Independence, and Normality

Two easy classroom examples are given of marginally normal random variables that are dependent but have zero correlation. One example is similar in nature to Anderson's well-known illustration that marginal normality does not imply joint normality.     

Preservation of dependence concepts under bivariate weighted distributions

ABSTRACT

In this paper, we provide conditions under which some bivariate dependence structures are preserved under bivariate weighted distributions. Bivariate weighted distributions whose dependence structure is the same as the original distribution are characterized. Finally, we discuss some examples to show the usefulness of our results.     

Dependence between oil and commodities markets using time-varying Archimedean copulas and effectiveness of hedging strategies

The aim of this work is to study in a first step the dependence between oil and some commodity prices (cotton, rice, wheat, sucre, coffee, and silver) using copula theory, and then in a second step to determine the optimal hedging strategy for oil–commodity portfolio against the risk of negative variation in commodity markets prices. The model is implemented with an AR-GARCH model with innovations that follow t distribution for the marginal distribution and the extreme value copula for the joint distribution and parameters and dependence indices are re-estimated in each new day which allow taking into account nonlinear dependence, tails behavior, and their development over time. Various copula functions are used to model the dependence structure between oil and commodity markets. Empirical results show an increase in the dependence during the last 6 years. Volatility for commodity prices registered record levels in the same time with the increase in uncertainty. Optimal hedging ratio varies over time as a consequence of the change in the dependence structure.     

Precise large deviations of aggregate claim amount in a dependent renewal risk model

In this paper, we consider a dependent risk model, in which the claim sizes are ofdependence structure, their inter-arrival times are independent, identically distributed (i.i.d.), and the claim size and its corresponding inter-arrival time satisfy a certain dependence structure described via the conditional distribution of the inter-arrival time given the subsequent claim size being large. We obtain the asymptotics of the lower and upper bounds of precise large deviations for the aggregate amount of claims, which holds uniformly for all x in an infinite interval of t.     

On a multivariate Lindley distribution

This article proposes a multivariate extension of the generalized Lindley distribution introduced by Abouammoh et al. (2015 Abouammoh, A.M., Alshangiti Arwa, M., Ragab, I.E. (2015). Reliability estimation of the generalized Lindley distributions. J. Stat. Comput. Simul. 85(17):3662–3678.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]). The proposed model is based on a probabilistic construction in which several Lindley random variables are connected by a common shock. Many statistical properties of this new distribution are explored. In particular, explicit forms of product moments, moment-generating function, and conditional moments are derived. Explicit expressions of moment-based estimators of the underlying parameters of the proposed model are established. Estimation using the maximum likelihood procedure is also investigated. Simulations attesting to the quality of the proposed estimators are presented. Application of the proposed model in reliability is also discussed.     

Dependence in the 2001 one-number census project

Summary.  The one-number census approach was developed by the Office for National Statistics to adjust the counts from the 2001 census of England and Wales for underenumeration. The method is underpinned by an assumption of independence between the count of the population that was given by the 2001 census and the count that was given by the Census Coverage Survey. Some dependence was, however, detected, and the paper describes the strategy that was used to measure dependence and to adjust the 2001 census population estimates.     

陕西对外贸易依存度的国内比较研究

2010年陕西省GDP突破万亿大关,跃升全国第十六位,但进出口总额仅名列全国第二十四位,对外贸易依存度远低于全国平均水平,陕西省外贸发展问题亟待研究。文章在分析世界和主要国家对外贸易依存度状况,以及部分国家对外贸易依存度与经济增长关系的基础上,说明对外贸易依存度的提高不仅是全球性趋势,而且与经济增长呈现正相关关系,进而通过省际比较,得出陕西对外贸易依存度过低的结论,并针对陕西对外贸易依存度过低的成因,提出加快陕西对外贸易发展的对策建议。     

制度缺位:影响素质教育有效性的内在因素——基于新制度经济学视角

素质教育推行多年,虽取得一定成就,但总体效果并不理想。其中一个重要原因就是政府在推行素质教育过程中的制度缺位。以西方新制度经济学的制度观为视角,通过分析教育制度、教育制度变迁及变迁过程中的路径依赖现象对推行素质教育的影响,从而得出,素质教育践行的有效性需要政府在制度安排层面提供制度性保障。     

意识形态的经济功能--诺斯的意识形态理论探析

西方主流经济学以理性选择模型为核心演绎出的一整套市场理论,面临着理论进一步发展的困境,在实践上也被认为失去了对现实问题的呼应.诺斯的意识形态理论是对理性选择模型富有成效的拯救性的扩展和修补.诺斯关于意识形态理论的经济功能、意识形态与制度变迁及制度变迁的路径依赖关系的详细分析,为西方经济学注入非理性因素和演化的思维,对经济学的发展具有重要意义,对于我们当前的政治、经济建设具有借鉴意义.     

GENERALIZED INTEGER-VALUED AUTOREGRESSION

The integer-valued AR1 model is generalized to encompass some of the more likely features of economic time series of count data. The generalizations come at the price of loosing exact distributional properties. For most specifications the first and second order both conditional and unconditional moments can be obtained. Hence estimation, testing and forecasting are feasible and can be based on least squares or GMM techniques. An illustration based on the number of plants within an industrial sector is considered.