巨灾风险：可保性与可负担性

 巨灾风险的可保性与可负担性,是保险在巨灾风险管理框架与机制中发挥作用并不可回避的重要前提。本文将巨灾风险的可保性与可负担性分别置入三种不同模式的框架下,从有别于传统只考虑可保性的单一视角,在分析讨论可保性与可负担性的理论基础以及相互关系等问题后,尝试性的探讨了三种巨灾风险管理模式框架下的可保性与可负担性。我们认为纯市场框架内,巨灾风险不可保且难于负担;政府与资本市场参与下的巨灾风险管理框架内,巨灾风险才成为可保风险并有限定的可负担。为此,融入保险机制的我国巨灾风险管理制度的创新,重构与建立政府、金融保险市场、商业保险业、监管机构以及社会公众的新型合作机制,将成为保险在巨灾风险管理制度中发挥重要作用的关键。     

死亡率预测模型的新进展

近半个世纪以来,世界范围内,人口死亡率整体上呈现下降趋势。而依据传统死亡模型对死亡率的预测往往高于实际水平,这给养老金财务安排和养老年金的成本核算带来了严重的不利影响。本文沿着死亡率模型的发展轨迹,回顾和总结了各类死亡率预测模型,对死亡率预测模型的最新进展做出评述,并对中国死亡率预测模型的选取给出了建议。     

The entropic measure transform

We introduce the entropic measure transform (EMT) problem for a general process and prove the existence of a unique optimal measure characterizing the solution. The density process of the optimal measure is characterized using a semimartingale BSDE under general conditions. The EMT is used to reinterpret the conditional entropic risk-measure and to obtain a convenient formula for the conditional expectation of a process that admits an affine representation under a related measure. The EMT is then used to provide a new characterization of defaultable bond prices, forward prices and futures prices when a jump-diffusion drives the asset. The characterization of these pricing problems in terms of the EMT provides economic interpretations as maximizing the returns subject to a penalty for removing financial risk as expressed through the aggregate relative entropy. The EMT is shown to extend the optimal stochastic control characterization of default-free bond prices of Gombani & Runggaldier (2013). These methods are illustrated numerically with an example in the defaultable bond setting. The Canadian Journal of Statistics 48: 97–129; 2020 © 2020 Statistical Society of Canada     

A Model of Aging and a Shape of the Observed Force of Mortality

A probabilistic model of aging is considered. It is based on the assumption that a random resource, a stochastic process of aging (wear) and the corresponding anti-aging process are embedded at birth. A death occurs when the accumulated wear exceeds the initial random resource. It is assumed that the anti-aging process decreases wear in each increment. The impact of environment (lifestyle) is also taken into account. The corresponding relations for the observed and the conditional hazard rate (force of mortality) are obtained. Similar to some demographic models, the deceleration of mortality phenomenon is explained via the concept of frailty. Simple examples are considered.     

Characterization of Continuous Distributions by Variance Bound and Its Implications to Reliability Modeling and Catastrophe Theory

We generalize some of the existing results on characterization of continuous distributions by lower bound on the variance and point out their equivalence to characterization of life distributions by relationship between conditional expectation and failure (reversed failure) rate. It is shown that these lower bounds are the same as, Cramer–Rao bound in the regular case and improves upon the latter in the non-regular case. Some applications to reliability modeling and catastrophe theory are pointed out.     

Bond Risk Premia Forecasting: A Simple Approach for Extracting Macroeconomic Information from a Panel of Indicators

We propose a simple but effective estimation procedure to extract the level and the volatility dynamics of a latent macroeconomic factor from a panel of observable indicators. Our approach is based on a multivariate conditionally heteroskedastic exact factor model that can take into account the heteroskedasticity feature shown by most macroeconomic variables and relies on an iterated Kalman filter procedure. In simulations we show the unbiasedness of the proposed estimator and its superiority to different approaches introduced in the literature. Simulation results are confirmed in applications to real inflation data with the goal of forecasting long-term bond risk premia. Moreover, we find that the extracted level and conditional variance of the latent factor for inflation are strongly related to NBER business cycles.     

我国可转换债券转股条款设计的实证研究

转股条款的灵活设计是实现可转债特定融资动因的重要途径之一,本文根据相关理论假说及其对证券条款设计的意义,设计了较为系统的实证分析框架和稳健的模型估计方法,对我国可转债的转股条款进行了较为严格意义上的实证检验。研究发现,高负债率、小规模和获取经营现金能力较差的公司明显倾向于设计较低的转股价格和较高的转换比率;信用记录较短（以上市年限代表）和收益不稳定的公司具有相同的倾向。国内可转债设计主要由财务危机假说解释,而制度性因素对条款设计具有重要影响。总体上,目前可转债的条款设计没有得到发行人的理性对待,本文就此提出了相关政策建议。     

The Ruin Probability of a Discrete-Time Risk Model with a One-Sided Linear Claim Process

In this article, the ruin probability is examined in a discrete time risk model with a constant interest rate, in which the dependent claims are assumed to have a one-sided linear structure. An explicit asymptotic formula is obtained for the ruin probability. Generalized Lundberg inequalities for the ruin probability are derived by martingale and inductive approaches.     

Expectations and Risk Premia at 8:30 a.m.: Deciphering the Responses of Bond Yields to Macroeconomic Announcements

What explains the sharp movements of the yield curve upon the release of major U.S. macroeconomic announcements? To answer this question, we estimate an arbitrage-free dynamic term structure model with macroeconomic fundamentals as risk factors. We assume that the yield curve reacts to announcements primarily because of the information they contain about the fundamentals of output, inflation, and the Fed’s inflation target. We model the updating process by linking the factor shocks to announcement surprises. Fitting this process to data on yield curve movements in 20-min event windows, we find that most major announcements, especially those about the labor market, are informative largely about the output gap rather than about inflation. The resulting changes in short-rate expectations account for the bulk of observed yield movements. But adjustments in risk premia are also sizable. In partly offsetting the effects of short-rate expectations, these adjustments help to account for the well-known hump-shaped pattern of yield reactions across maturities.     

Risk inflation of sequential tests controlled by alpha investing

Streaming feature selection is a greedy approach to variable selection that evaluates potential explanatory variables sequentially. It selects significant features as soon as they are discovered rather than testing them all and picking the best one. Because it is so greedy, streaming selection can rapidly explore large collections of features. If significance is defined by an alpha investing protocol, then the rate of false discoveries will be controlled. The focus of attention in variable selection, however, should be on fit rather than hypothesis testing. Little is known, however, about the risk of estimators produced by streaming selection and how the configuration of these estimators influences the risk. To meet these needs, we provide a computational framework based on stochastic dynamic programming that allows fast calculation of the minimax risk of a sequential estimator relative to an alternative. The alternative can be data driven or derived from an oracle. This framework allows us to compute and contrast the risk inflation of sequential estimators derived from various alpha investing rules. We find that a universal investing rule performs well over a variety of models and that estimators allowed to have larger than conventional rates of false discoveries produce generally smaller risk.     

On periodic autoregressive stochastic volatility models: structure and estimation

To capture both the volatility evolution and the periodicity feature in the autocorrelation structure exhibited by many nonlinear time series, a Periodic AutoRegressive Stochastic Volatility (PAR-SV ) model is proposed. Some probabilistic properties, namely the strict and second-order periodic stationarity, are provided. Furthermore, conditions for the existence of higher-order moments are established. The autocovariance structure of the squares and higher order powers of the PAR-SV process is studied. Its dynamic properties are shown to be consistent with financial time series empirical findings. Ways in which the model may be estimated are discussed. Finally, a simulation study of the performance of the proposed estimation methods is provided and the PAR-SV is applied to model the spot rates of the euro and US dollar both against the Algerian dinar. The empirical analysis shows that the proposed PAR-SV model can be considered as a viable alternative to the periodic generalized autoregressive conditionally heteroscedastic (PGARCH) model.     

The analysis of partially-censored date from a fitst-order semi-markov model

This paper describes a Fortran program for analyzing partially-censored data from a firstorder semi-Markov model. Nonparametric maximum likelihood estimates and estimates of their corresponding covariance matrices are computed based on the results of Lagakos, Sornmer and Zelen (1978). The program can be applied to data arising from a wide array of multistate stochastic processes. The program's required input and output are discussed and illustrated using the data from a recent lung cancer clinical trial.     

Investigation of disease-free survival as a surrogate endpoint for survival in cancer clinical trials

A stochastic model wiuh exponential components is used to describe our data collected from a phase III cancer clinical trial. Criteria which guarantee that disease-free survival (DFS) can be used as a surrogate for overall survival are explored under this model. We examine several colorectal adjuvant clinical trials and find that these conditions are not satisfied. The relationship between the hazard ratio of DFS for an active treatment versus a control treatment and the cumulative hazard ratio of survival for the same two treatments is then explored. An almost linear relationship is found such that a hazard ratio for DFS of less than a threshold R corresponds to a non-null treatment effect on survival The threshold value R is determined for our colorectal adjuvant trial data. Based on this relationship, a one-sided test of equal hazard rate of survival is equivalent to a test of hazard ratio of DFS small than R This approach assumes that recurrence information is unbiasedly and accurately assessed; an assumpion which is sometimes difficult to ensure for multicenter clinical trials, particularly for interim analyses.     

我国宏观金融风险测度研究

文章根据统计指标体系的构建原则,建立了由宏观经济环境、银行呆坏账、泡沫、国债和外资冲击在内的宏观金融风险测度指标体系,利用映射法原则将原始指标区间化。然后根据层次分析法确定风险权重,进而构造了我国宏观金融风险测度的理论模型。     

The Ornstein-Uhlenbeck Dirichlet process and other time-varying processes for Bayesian nonparametric inference

This paper introduces a new class of time-varying, measure-valued stochastic processes for Bayesian nonparametric inference. The class of priors is constructed by normalising a stochastic process derived from non-Gaussian Ornstein-Uhlenbeck processes and generalises the class of normalised random measures with independent increments from static problems. Some properties of the normalised measure are investigated. A particle filter and MCMC schemes are described for inference. The methods are applied to an example in the modelling of financial data.     

Vitamin A and Infant Mortality: Beyond Intention-to-Treat in a Randomized Trial

This paper investigates the effect of one dose of vitamin A on subsequent 4 month mortality in children under 6 months of age in a randomized, double-blind placebo-controlled community trial in Nepal. An earlier published intention-to-treat analysis showed no benefit, but ignored the information on actual receipt of treatment. Structural failure time models (Robins and Tsiatis, '91) use randomization based inference and incorporate compliance information which is possibly selective. The data presented here offer some new challenges for this approach: ward-based randomization induces correlation between survival outcomes; and the actual receipt of vitamin A dose is not always recorded. To tackle the problem of the clustered survival data we consider a robust version of the structural parameter vector estimator. A sensitivity analysis captures boundaries for the estimated structural parameters reflecting a range of potential values of children whose true receipt of treatment is unknown. The analysis suggests that the effect of vitamin A was beneficial in the beginning of the trial but towards the end of the trial there was a reversal of this effect.     

Application of a stochastic model to response assessments in a study of squamous cell carcinoma of the head and neck

This paper discusses the application of a stochastic model in the analysis of response assessments made at various time points in a clinical trial of patients with squamous cell carcinoma of the head and neck. The transition rates and probabilities during treatment administration are derived using maximum likelihood methods. The results are then compared with the standard analyses used in solid tumour studies. Stochastic modelling is considered to complement the standard analyses, provide a holistic approach and better explain the underlying disease process. Copyright © 2012 John Wiley & Sons, Ltd.     

Checking a Semiparametric Additive Risk Model

McKeague and Sasieni [A partly parametric additive risk model. Biometrika 81 (1994) 501] propose a restriction of Aalen’s additive risk model by the additional hypothesis that some of the covariates have time-independent influence on the intensity of the observed counting process. We introduce goodness-of-fit tests for this semiparametric Aalen model. The asymptotic distribution properties of the test statistics are derived by means of martingale techniques. The tests can be adjusted to detect particular alternatives. As one of the most important alternatives we consider Cox’s proportional hazards model. We present simulation studies and an application to a real data set.     

Statistical inference for a relaxation index of stochastic dominance under density ratio model

Stochastic dominance is usually used to rank random variables by comparing their distributions, so it is widely applied in economics and finance. In actual applications, complete stochastic dominance is too demanding to meet, so relaxation indexes of stochastic dominance have attracted more attention. The π index, the biggest gap between two distributions, can be a measure of the degree of deviation from complete dominance. The traditional estimation method is to use the empirical distribution functions to estimate it. Considering the populations under comparison are generally of the same nature, we can link the populations through density ratio model under certain condition. Based on this model, we propose a new estimator and establish its statistical inference theory. Simulation results show that the proposed estimator substantially improves estimation efficiency and power of the tests and coverage probabilities satisfactorily match the confidence levels of the tests, which show the superiority of the proposed estimator. Finally we apply our method to a real example of the Chinese household incomes.     

Ruin Probabilities of a Dual Markov-Modulated Risk Model

This article is devoted to studying a dual Markov-modulated risk model, which can properly represent, to some extent, surplus processes of companies that pay costs continuously and have occasional gains. We consider both the finite and infnite horizon ruin probabilities under this dual model. Upper and lower bounds of Lundberg type are derived for these ruin probabilities. We also obtain a time-dependent version of Lundberg type inequalities.