Bayesian analysis of multivariate stochastic volatility with skew return distribution

Multivariate stochastic volatility models with skew distributions are proposed. Exploiting Cholesky stochastic volatility modeling, univariate stochastic volatility processes with leverage effect and generalized hyperbolic skew t-distributions are embedded to multivariate analysis with time-varying correlations. Bayesian modeling allows this approach to provide parsimonious skew structure and to easily scale up for high-dimensional problem. Analyses of daily stock returns are illustrated. Empirical results show that the time-varying correlations and the sparse skew structure contribute to improved prediction performance and Value-at-Risk forecasts.     

Monte carlo estimates of the distributions of the random polygons of the voronoi tessellation with respect to a poisson process

A large-scale study, in which two million random Voronoi polygons (with respect to a homogeneous Poisson point process) were generated and mensurated, is described. The polygon characteristics recorded are number of sides (or vertices), perimeter, area and interior angles. A feature is the efficient “quantile” method of replicating Poisson-type random structures, which it is hoped may find useful application elsewhere.     

“亡(彳)”非“无吝”说

殷墟卜 辞命辞中的“亡(彳)”一词,丁山先生释读为“无尤”.半个世纪以来,学术界并无异议.近年来有学者提出新说,认为“(彳)”字应该是“拇”字的表意初文；又据声韵将其读作“吝”,“亡(彳)”就是《周易》、《归藏》等卜筮类文献的“无吝”.这个词汇在殷墟卜辞中出现频率很高,且与卜辞释读关系甚大,因此仍有进一步讨论的必要.分析该字字形以及“无吝”一词产生年代,此新说不能成立,丁山先生将“亡(彳)”释读为“无尤”应是可信的.     

侵权法中的作为义务探究

国外立法例对侵权法中作为义务的规制模式不尽相同,中国台湾地区和大陆地区理论界对作为义务的研究在结合中国司法实践方面略显不足。对于侵权法中作为义务的探究,应当将国外立法例、中国理论界的研究成果与司法实践情况结合起来。中国侵权法中作为义务的设计应当遵循如下思路:无须在一般条款中明确作为义务;合同约定不应成为侵权法中作为义务的来源;不应当规定一般救助义务;作为义务来源应当具有层级性,且该层级性应当以重塑安全保障义务为中心。     

Editorial collaborators

A simulation study of the binomial-logit model with correlated random effects is carried out based on the generalized linear mixed model (GLMM) methodology. Simulated data with various numbers of regression parameters and different values of the variance component are considered. The performance of approximate maximum likelihood (ML) and residual maximum likelihood (REML) estimators is evaluated. For a range of true parameter values, we report the average biases of estimators, the standard error of the average bias and the standard error of estimates over the simulations. In general, in terms of bias, the two methods do not show significant differences in estimating regression parameters. The REML estimation method is slightly better in reducing the bias of variance component estimates.     

Guerrilla selfhood: imagining young people's entrepreneurial futures

In this paper, we argue that complex forms of selfhood emerge in relation to rapid economic and social changes unfolding in the early stages of the twenty-first century. We draw on literature that explores youth at risk, entrepreneurial selfhood and neoliberalism to argue that young people are developing modes of transition that allow them to acclimatise to economic and social insecurity. It is an insecurity borne of a paradoxical reliance on, and failure of, neoliberal forms of economics and society. In the context of a post-Global Financial Crisis (post-GFC) world, we explore how young people take responsibility for their uncertain futures. Via our critique of how young people are supposed to manage their lives from education to employment, we argue that a form of selfhood emerges as they are challenged by limited education and employment opportunities. We call this selfhood the guerrilla self. We use this term to designate types of identity that require participation through resistance, institutionalisation through the appearance of not being institutionalised, and individualism in the midst of a failure of individualism. In making this case, we draw on stories told by young people in the USA planning for a future in a post-GFC world.     

Is prenatal sex selection associated with lower female child mortality?

I examine whether prenatal sex selection has substituted postnatal excess female mortality by analysing the dynamics of child sex ratios between 1980 and 2015 using country-level life table data. I decompose changes in child sex ratios into a ‘fertility’ component attributable to prenatal sex selection and a ‘mortality’ component attributable to sex differentials in postnatal survival. Although reductions in numbers of excess female deaths have accompanied increases in missing female births in all countries experiencing the emergence of prenatal sex selection, relative excess female mortality has persisted in some countries but not others. In South Korea, Armenia, and Azerbaijan, mortality reductions favouring girls accompanied increases in prenatal sex selection. In India, excess female mortality was much higher and largely stable as prenatal sex selection emerged, but slight reductions were seen in the 2000s. In China, although absolute measures showed reductions, relative excess female mortality persisted as prenatal sex selection increased.     

拥有自有品牌零售商的平台开放策略研究

随着电子商务的快速发展，零售商之间竞争加剧，自有品牌战略成为零售商获取竞争优势的关键。研究拥有自有品牌零售商的平台开放策略，通过对比零售商不开放平台和开放平台下的均衡利润，给出零售商平台开放策略选择条件，并分析产品之间价格影响系数、固定成本和潜在需求差异系数对零售商平台开放策略选择的影响，最后结合数值分析和京东自有品牌的发展现状验证了本文的主要研究结论。研究发现：第一，随着固定成本的增加，佣金费率逐渐减少，随着潜在需求差异系数的增加，佣金费率逐渐增加；第二，当产品之间的价格影响系数较小（较大）时，平台开放（不开放）是零售商的最优选择；第三，当固定成本较小（较大）时，平台开放（不开放）是零售商的最优选择；第四，当潜在需求差异系数较小（较大）时，平台开放（不开放）是零售商的最优选择。