Kalman滤波在未决赔款准备金评估中的应用

未决赔款准备金是非寿险公司负债的主要构成部分,提高对其评估的精度有着重要的意义。动态模型能够提高未决赔款准备金评估的精度,在动态模型中最重要的是Kalman滤波模型。文章运用Kalman滤波模型进行了未决赔款准备金评估,并对其进行了研究分析。     

基于GB2分布的贝叶斯相依性准备金评估模型

非寿险精算的核心问题之一是对未决赔款准备金进行准确评估。非寿险未决赔款准备金评估通常使用增量赔款或累积赔款的流量三角形数据。在未决赔款准备金评估中,多条业务线的流量三角形数据之间通常存在一定的相依关系,这种相依关系对保险公司总准备金的评估结果具有重要影响。从本质上看,未决赔款准备金是一个随机变量,其损失分布存在一定的多样性。因此,在未决赔款准备金的评估中选择合适的分布至关重要。GB2分布是一种包含四个参数的连续型分布,具有灵活的密度函数,分布形状更加灵活,许多常见分布都是它的特例,适宜处理不同特点的未决赔款流量三角形数据。为了考虑不同业务线之间的相依关系对未决赔款准备金评估结果的影响,本文基于GB2分布建立了一种相依性准备金评估模型,该模型首先假设不同业务线的增量赔款服从GB2分布,并在分布的期望中引入事故年和进展年作为解释变量,引入日历年随机效应描述各条业务线之间的相依关系;然后借助贝叶斯HMC方法进行参数估计和未决赔款准备金预测,最后给出了总准备金的预测分布和评估结果。本文将该方法应用到两条业务线的流量三角形数据进行实证研究,并与现有其他方法进行了比较。实证研究结果表明,基于GB2分布的相依性准备金评估模型对未决赔款准备金的尾部风险和不确定性的考虑更加充分,更加适用于评估具有厚尾或者长尾特征的准备金数据。     

非寿险准备金评估的广义线性模型

在非寿险准备金评估实务中,保险公司通常应用链梯法和B-F法等确定性模型,但这类模型无法对准备金的预测结果进行统计检验,因此广义线性模型受到了越来越多的关注.在假设增量赔款服从指数分布族的情况下,讨论广义线性模型在准备金评估中的应用,并通过一个实际的流量三角形数据进行实证检验.     

运用动态线性模型对未决赔款准备金的评估

随机准备金评估方法不仅可以得到准备金的估计值,还能够得到评估的精度.本文介绍了将随机方法与传统链梯法联系,结合Kalman滤波建立的动态线性模型,并运用动态线性模型对我国非寿险公司的数据进行评估.结果表明,运用动态线性模型评估未决赔款准备金可提高评估精度,并能够对模型参数进行校核.     

应用对数正态模型对未决赔款准备金的评估

未决赔款准备金的谨慎提取对保险公司的稳健经营具有非常重要的意义。由于赔付情况的不确定性和不稳定性.实务中越来越关注未决赔款准备金评估的精度。文章基于增量赔付的对数正态模型,给出了准备金的估计值和预测的精度。最后通过一具体实例说明本文方法的有效性,并同链梯法进行了比较。     

未决赔款准备金评估的Mack模型及其预测均方误差的实现

目前,在我国精算实务中对未决赔款准备金评估的不确定性风险逐渐重视,对不确定性加以度量显得很有必要。传统链梯法是未决赔款准备金评估最常用的确定性方法,链梯法应用流量三角形评估未来赔款进展模式,将随机性模型和链梯法结合起来就得到随机链梯法。其中,对于非参数随机链梯法已有深入的研究,该方法直接对传统链梯法的假设步骤建立随机模型,而且没有具体的赔款额分布假设。这种度量估计的不确定性,对准备金负债评估的准确性和充足性具有重要的参考价值。文章利用Mack模型得到了未决赔款准备金的预测均方误差,并通过数值例子进行了说明。     

基于非参数Bootstrap方法的随机性链梯法及R实现

在我国目前精算实务中,未决赔款准备金评估的不确定性风险逐渐得到重视,对不确定性加以度量显得很有必要。传统链梯法是未决赔款准备金评估最常用的确定性方法,而过度分散泊松模型是与传统链梯法等价的随机性模型,在过度分散泊松模型下,准备金的极大似然估计和传统链梯法的估计值相同。文章把非参数Bootstrap方法应用于过度分散泊松模型中,得到了未决赔款准备金的预测均方误差和预测分布,并通过精算实务中的数值实例应用R软件加以了实证分析。     

广义线性滤波模型在非寿险准备金评估中的应用

文章在非寿险未决赔款准备金评估中,借鉴状态空间模型如Kalman滤波在准备金评估中的应用,以广义线性模型为基础,通过在贝叶斯估计中利用泰勒展开式的二阶近似式构造了离散指数族内的后验似然函数,生成广义线性滤波,可实现动态广义线性模型的参数估计,从而能够向模型中引入新的观测数据递归出更新的参数估计结果。文章通过实例演示了伽玛广义线性滤波模型在准备金评估中的应用。     

未决赔款准备金评估的双广义线性模型的改进

文章运用双广义线性模型,将通货膨胀、气候环境这两个外部因素与公司理赔政策这一内部因素引入到广义线性模型中,对一般的广义线性模型进一步改进.然后利用实际数据,应用改进后的模型,进行实证分析,并与未改进的评估模型得到的相关数据进行了比较,最后分析了未决赔款准备金评估结果变化的原因.     

分层模型在非寿险精算学中的应用研究评述

 本文结合非寿险精算中普遍存在的具有层次性及相关性的数据结构,在分层模型的全新视角下,充分借鉴分层模型的理论研究成果,对分层模型在非寿险定价与索赔准备金评估中的应用研究的最新成果进行了系统梳理和总结,并将贝叶斯方法、随机模拟、信度理论、数据分析技术、科学计算等融合其中。在此基础上,提出了一些有待深入探索和进一步扩展的新思路。这对提升我国非寿险精算学科的统计分析体系,促进我国非寿险精算学科的发展具有重要的科学研究意义。     

Performances of Bayesian model selection criteria for generalized linear models with non-ignorably missing covariates

This article deals with model comparison as an essential part of generalized linear modelling in the presence of covariates missing not at random (MNAR). We provide an evaluation of the performances of some of the popular model selection criteria, particularly of deviance information criterion (DIC) and weighted L (WL) measure, for comparison among a set of candidate MNAR models. In addition, we seek to provide deviance and quadratic loss-based model selection criteria with alternative penalty terms targeting directly the MNAR models. This work is motivated by the need in the literature to understand the performances of these important model selection criteria for comparison among a set of MNAR models. A Monte Carlo simulation experiment is designed to assess the finite sample performances of these model selection criteria in the context of interest under different scenarios for missingness amounts. Some naturally driven DIC and WL extensions are also discussed and evaluated.     

Testing non-nested log-linear models with pseudo estimator

As the number of random variables for the categorical data increases, the possible number of log-linear models which can be fitted to the data increases rapidly, so that various model selection methods are developed. However, we often found that some models chosen by different selection criteria do not coincide. In this paper, we propose a comparison method to test the final models which are non-nested. The statistic of Cox (1961, 1962) is applied to log-linear models for testing non-nested models, and the Kullback-Leibler measure of closeness (Pesaran 1987) is explored. In log-linear models, pseudo estimators for the expectation and the variance of Cox's statistic are not only derived but also shown to be consistent estimators.     

Generalized partially linear varying-coefficient models

Generalized varying-coefficient models are useful extensions of generalized linear models. They arise naturally when investigating how regression coefficients change over different groups characterized by certain covariates such as age. In this paper, we extend these models to generalized partially linear varying-coefficient models, in which some coefficients are constants and the others are functions of certain covariates. Procedures for estimating the linear and non-parametric parts are developed and their associated statistical properties are studied. The methods proposed are illustrated using some simulations and real data analysis.     

Simulations on the Jelinski-Moranda model of software reliability; application of some parametric bootstrap methods

In software reliability theory many different models have been proposed and investigated. some of these models intuitively match reality better than others. The properties of certain statistical estimation procedures in connection with these models are also model-dependent. In this paper we investigate how well the maximum likelihood estimation procedure and the parametric bootstrap behave in the case of the very well-known software reliability model suggested by Jelinski and Moranda (1972). For this study we will make use of simulated data.     

Bayesian model comparison based on expected posterior priors for discrete decomposable graphical models

The implementation of the Bayesian paradigm to model comparison can be problematic. In particular, prior distributions on the parameter space of each candidate model require special care. While it is well known that improper priors cannot be routinely used for Bayesian model comparison, we claim that also the use of proper conventional priors under each model should be regarded as suspicious, especially when comparing models having different dimensions. The basic idea is that priors should not be assigned separately under each model; rather they should be related across models, in order to acquire some degree of compatibility, and thus allow fairer and more robust comparisons. In this connection, the intrinsic prior as well as the expected posterior prior (EPP) methodology represent a useful tool. In this paper we develop a procedure based on EPP to perform Bayesian model comparison for discrete undirected decomposable graphical models, although our method could be adapted to deal also with directed acyclic graph models. We present two possible approaches. One based on imaginary data, and one which makes use of a limited number of actual data. The methodology is illustrated through the analysis of a 2×3×4 contingency table.     

社会保障基金长期财务随机预测模型的比较与选择

为了测算分析社会保障制度的可持续发展,世界上不少国家建立了社会保障基金长期财务预测模型。与确定性财务预测模型相比,随机预测模型有利于阐明预测结果所面临的不确定。美国在运用随机预测模型对社会保障基金的财务状况做出预测方面走在世界最前端,我国对社会保障基金随机预测模型的研究基本处于空白。本文对美国社会保障署和国会预算办公室采用的社会保障基金长期随机预测模型进行了比较分析,对两种模型的选择给出了建议,最后提出了我国建立社会保障基金长期预测模型的一些建议。     

A new class of survival regression models with heavy-tailed errors: robustness and diagnostics

Birnbaum-Saunders models have largely been applied in material fatigue studies and reliability analyses to relate the total time until failure with some type of cumulative damage. In many problems related to the medical field, such as chronic cardiac diseases and different types of cancer, a cumulative damage caused by several risk factors might cause some degradation that leads to a fatigue process. In these cases, BS models can be suitable for describing the propagation lifetime. However, since the cumulative damage is assumed to be normally distributed in the BS distribution, the parameter estimates from this model can be sensitive to outlying observations. In order to attenuate this influence, we present in this paper BS models, in which a Student-t distribution is assumed to explain the cumulative damage. In particular, we show that the maximum likelihood estimates of the Student-t log-BS models attribute smaller weights to outlying observations, which produce robust parameter estimates. Also, some inferential results are presented. In addition, based on local influence and deviance component and martingale-type residuals, a diagnostics analysis is derived. Finally, a motivating example from the medical field is analyzed using log-BS regression models. Since the parameter estimates appear to be very sensitive to outlying and influential observations, the Student-t log-BS regression model should attenuate such influences. The model checking methodologies developed in this paper are used to compare the fitted models.     

Comparison of Shared Frailty Models for Kidney Infection Data under Exponential Power Baseline Distribution

Shared frailty models are often used to model heterogeneity in survival analysis. There are certain assumptions about the baseline distribution and distribution of frailty. In this paper, four shared frailty models with frailty distribution gamma, inverse Gaussian, compound Poisson, and compound negative binomial with exponential power as baseline distribution are proposed. These models are fitted using Markov Chain Monte Carlo methods. These models are illustrated with a real life bivariate survival data set of McGilchrist and Aisbett (1991) related to kidney infection, and the best model is suggested for the data using different model comparison criteria.     

Nondifferentiable errors in beta-compliance integrated logistic models: numerical results

In dose-response models, there are cases where only a portion of the administered dose may have an effect. This results in a stochastic compliance of the administered dose. In a previous paper (Chen-Mok and Sen, 1999), we developed suitable adjustments for compliance in the logistic model under the assumption of nondifferential measurement error. These compliance-adjusted models were categorized into three types: (i) Low (or near zero) dose levels, (ii) moderate dose levels, and (iii) high dose levels. In this paper, we analyze a set of data on the atomic bomb survivors of Japan to illustrate the use of the proposed methods. In addition, we examine the performance of these methods under different conditions based on a simulation study. Among all three cases, the adjustments proposed for the moderate dose case do not seem to work adequately. Both bias and variance are larger when using the adjusted model in comparison with the unadjusted model. The adjustments for the low dose case seem to work in reducing the bias in the estimation of the parameters under all types of compliance distributions. The MSEs, however, are larger under some of the compliance distribution considered. Finally, the results of this simulation study show that the adjustments for the high dose case are successful in achieving both a reduction in bias as well as a reduction in MSE, hence the overall efficiency of the estimation is improved.     

Logistic与分类树模型变量筛选的比较——基于信用卡邮寄业务响应率分析

基于信用卡邮寄业务响应率分析来讨论Logistic模型和分类树模型在变量选取上的区别,并尝试从几个不同角度去解释两类模型变量筛选差异的原因。笔者认为没有绝对占优势的方法,需要结合具体场景和模型的特点来选择合适的模型。分类树模型在训练集上容易过度拟合,对单个变量的影响很敏感,在进行危险因素分析时结果更能强调危险因素,对孤立点的识别率很高。Logistic模型容易受到解释变量依存关系的影响,加上分类变量的影响容易过多地选入变量或者因子,对孤立点敏感,对噪点不敏感。判别函数的差异是变量筛选差异的关键因素。