Theory of Bilinear Time Series Models

ABSTRACT

In this paper, we prove some theoretic properties of bilinear time series models which are extension of ARMA models. The sufficient conditions for asymptotic stationarity and ivertibility of some types of bilinear models are derived. The structural theory of discussed bilinear models is similar to that of ARMA models. For illustration, a bilinear model has been fitted to the Wolfer sunspot numbers and a substantial reduction in sum of squared residuals is obtained as comparing with Box-Jenkins ARMA model.     

A detection algorithm for the first jump time in sample trajectories of jump-diffusions driven by α-stable white noise

Abstract

The purpose of this paper is to develop a detection algorithm for the first jump point in sampling trajectories of jump-diffusions which are described as solutions of stochastic differential equations driven by α-stable white noise. This is done by a multivariate Lagrange interpolation approach. To this end, we utilize computer simulation algorithm in MATLAB to visualize the sampling trajectories of the jump-diffusions for various combinations of parameters arising in the modeling structure of stochastic differential equations.     

Cointegrated systems II

The three invited papers in this special issue of Econometric Reviews on "Cointegrated Systems II" complement the previous special issue of the journal. The paper by Eric Zivot and Peter Phillips provides a comprehensive Bayesian analysis of trend determination in economic time series. Two interesting comments on some aspects of current research involving cointegration and the modelling of dynamic economic relationships are provided by Clive Granger and Denzil Fiebig.     

中国功能性分配格局的国际比较研究

 在当前的研究文献中,我国学者在对中国劳动收入份额进行国际比较时,通常在两个方面产生混乱：一是我国收入法GDP中的劳动者报酬指标包含了非公司业主的混合收入,采用的是宽口径的概念,而SNA1993中的雇员报酬概念却并不包括混合收入,是窄口径的概念。因此,根据我国收入法GDP数据直接计算出的劳动收入份额并不具有国际可比性;二是2004年我国收入法GDP的统计口径本身发生了变动,使得我国2004年前后的劳动收入份额也不具有可比性。本文首先以2004年的经济普查数据为基础,对自我雇佣者的混合收入按照宽、中、窄三种口径进行调整,基本消除了上述的两个不可比因素;其次,以调整后的可比数据为基础,本文对我国宽、中、窄口径的劳动收入份额进行了全面的国际比较,得到的结论更为稳健可靠。结果发现：如果采用窄口径的劳动报酬概念,我国的劳动收入份额不仅低于发达国家的平均水平15～20个百分点,也低于发展中国家的平均水平超过4个百分点。     

Exact Likelihood Equations for Autoregression Models with Multivariate Elliptically Contoured Distributions

Abstract

The multivariate elliptically contoured distributions provide a viable framework for modeling time-series data. It includes the multivariate normal, power exponential, t, and Cauchy distributions as special cases. For multivariate elliptically contoured autoregressive models, we derive the exact likelihood equations for the model parameters. They are closely related to the Yule-Walker equations and involve simple function of the data. The maximum likelihood estimators are obtained by alternately solving two linear systems and illustrated using the simulation data.     

Consistency of the normal equations

This note provides an alternative proof of consistency of the normal equations by appealing to well-known results in linear programming.     

Maximum Likelihood Estimation for Stochastic Differential Equations with Random Effects

Abstract. We consider N independent stochastic processes (X _i (t), t ∈ [0,T _i ]), i=1,…, N, defined by a stochastic differential equation with drift term depending on a random variable φ _i . The distribution of the random effect φ _i depends on unknown parameters which are to be estimated from the continuous observation of the processes X_i. We give the expression of the exact likelihood. When the drift term depends linearly on the random effect φ _i and φ _i has Gaussian distribution, an explicit formula for the likelihood is obtained. We prove that the maximum likelihood estimator is consistent and asymptotically Gaussian, when T _i =T for all i and N tends to infinity. We discuss the case of discrete observations. Estimators are computed on simulated data for several models and show good performances even when the length time interval of observations is not very large.     

Robust Correlation Structure for Multivariate Failure Time Data

When incomplete repeated failure times are collected from a large number of independent individuals, interest is focused primarily on the consistent and efficient estimation of the effects of the associated covariates on the failure times. Since repeated failure times are likely to be correlated, it is important to exploit the correlation structure of the failure data in order to obtain such consistent and efficient estimates. However, it may be difficult to specify an appropriate correlation structure for a real life data set. We propose a robust correlation structure that can be used irrespective of the true correlation structure. This structure is used in constructing an estimating equation for the hazard ratio parameter, under the assumption that the number of repeated failure times for an individual is random. The consistency and efficiency of the estimates is examined through a simulation study, where we consider failure times that marginally follow an exponential distribution and a Poisson distribution is assumed for the random number of repeated failure times. We conclude by using the proposed method to analyze a bladder cancer dataset.     

非线性时滞差分方程解的振动性

讨论了时滞差分系统yn＋1－yn＋Pnf（yn－k）＝0n＝0,1,2,...（y≠0）的振动性,得到了上式方程解振动的一组充分条件．     

耦合KdV方程组的孤波精确解

本文利用一种简明的方法得出一类耦合KdV方程组的孤波精确解。