Moment-Implied Densities: Properties and Applications

Suppose one uses a parametric density function based on the first four (conditional) moments to model risk. There are quite a few densities to choose from and depending on which is selected, one implicitly assumes very different tail behavior and very different feasible skewness/kurtosis combinations. Surprisingly, there is no systematic analysis of the tradeoff one faces. It is the purpose of the article to address this. We focus on the tail behavior and the range of skewness and kurtosis as these are key for common applications such as risk management.     

More on the four-parameter kappa distribution

The generalized extreme-value has been the distribution of choice for modeling available maxima (or minima) data since theory has shown it to be the limiting form of the distribution of extremes. However, fits to finite samples are not always adequate. Hosking (1994) and Parida (1999) suggest the four-parameter Kappa distribution as an alternative. Hosking (1994) developed an L-moment procedure for estimation. Some compromises must be made in practice however, as seen in Parida (1999). L-moment estimators of the four-parameter Kappa distribution are not always computable nor feasible. A simulation study in this paper quantifies the extent of each problem. Maximum likelihood is investigated as an alternative method of estimation and a simulation study compares the performance of both methods of estimation. Finally, further benefits of maximum likelihood are shown when wind speeds From the Tropical Pacific are examined and the weekly maxima for 10 buoys in the area are analyzed.     

Forecasting with serially correlated regression models

In this article we investigate the asymptotic and finite-sample properties of predictors of regression models with autocorrelated errors. We prove new theorems associated with the predictive efficiency of generalized least squares (GLS) and incorrectly structured GLS predictors. We also establish the form associated with their predictive mean squared errors as well as the magnitude of these errors relative to each other and to those generated from the ordinary least squares (OLS) predictor. A large simulation study is used to evaluate the finite-sample performance of forecasts generated from models using different corrections for the serial correlation.     

Concurrent generation of multivariate mixed data with variables of dissimilar types

ABSTRACT

Data sets originating from wide range of research studies are composed of multiple variables that are correlated and of dissimilar types, primarily of count, binary/ordinal and continuous attributes. The present paper builds on the previous works on multivariate data generation and develops a framework for generating multivariate mixed data with a pre-specified correlation matrix. The generated data consist of components that are marginally count, binary, ordinal and continuous, where the count and continuous variables follow the generalized Poisson and normal distributions, respectively. The use of the generalized Poisson distribution provides a flexible mechanism which allows under- and over-dispersed count variables generally encountered in practice. A step-by-step algorithm is provided and its performance is evaluated using simulated and real-data scenarios.     

Performance of a bartlett-type modification for the deviance

Cordeiro (1983) has derived the expected value of the deviance for generalized linear models correct to terms of order n ^-1 being the sample size. Then a Bartlett-type factor is available for correcting the first moment of the deviance and for fitting its distribution. If the model is correct, the deviance is not, in general, distributed as chi-squared even asymptotically and very little is known about the adequacy of the X ² approximation. This paper through simulation studies examines the behaviour of the deviance and a Bartlett adjusted deviance for testing the goodness-of-fit of a generalized linear model. The practical use of such adjustment is illustrated for some gamma and Poisson models. It is suggested that the null distribution of the adjusted deviance is better approximated by chi-square than the distribution of the deviance.     

Testing Hypotheses About the Number of Factors in Large Factor Models

In this paper we study high‐dimensional time series that have the generalized dynamic factor structure. We develop a test of the null of k₀ factors against the alternative that the number of factors is larger than k₀ but no larger than k₁>k₀. Our test statistic equals max_{k0<k k1}(γ_k−γ_k+1)(γ_k+1−γ_k+2), where γ_i is the ith largest eigenvalue of the smoothed periodogram estimate of the spectral density matrix of data at a prespecified frequency. We describe the asymptotic distribution of the statistic, as the dimensionality and the number of observations rise, as a function of the Tracy–Widom distribution and tabulate the critical values of the test. As an application, we test different hypotheses about the number of dynamic factors in macroeconomic time series and about the number of dynamic factors driving excess stock returns.     

普惠制养老保障——让农民老有所养不再是梦

我国即将全面进入老龄化社会,农村社会老龄化速度加快,同时随着城市化进程的加快,农村传统的土地养老和家庭养老功能逐渐弱化。而我国现有的社会养老保障制度呈现出的＂城乡二元＂结构,导致农村养老保险出现的制度缺失和缺陷,不利于实现＂人人均等享受公共服务＂的目标。因此,必须建立农村社会养老保险制度体系,促进农村社会和谐发展。     

Citizen Support for Hospital Privatization: A Hierarchical Cross-National Analysis

The movement for a new public management (NPM) holds that citizens will put aside partisan and ideological differences to support more efficient service delivery. Focusing on hospital privatization, a multi-national sample is utilized to investigate this assertion. Generalized hierarchical linear modeling (GHLM) is employed as the method of statistical analysis. The findings with regard to privatizing hospitals reveal that citizens develop their policy position by reference to a combination of symbolic political variables, service demand, self-interest, information levels, and political efficacy. The results cast doubt on the assertion that partisan differences will be set aside as citizens consider privatization reforms.

Estimation and inference for generalized semi-varying coefficient models

This paper is concerned with the estimation and inference in generalized semi-varying coefficient models. An orthogonal projection local quasi-likelihood estimation is investigated, which can easily be used to estimate the model parametric and nonparametric parts. Then an empirical likelihood logarithmic approach to construct the confidence regions/intervals of the nonparametric parts is developed. Under some mild conditions, the asymptotic properties of the resulting estimators are studied explicitly, respectively. Some simulation studies are carried out to examine the finite sample performance of the proposed methods. Finally, the methodologies are illustrated by a real data set.     

Comparative GMM and GQL logistic regression models on hierarchical data

We often rely on the likelihood to obtain estimates of regression parameters but it is not readily available for generalized linear mixed models (GLMMs). Inferences for the regression coefficients and the covariance parameters are key in these models. We presented alternative approaches for analyzing binary data from a hierarchical structure that do not rely on any distributional assumptions: a generalized quasi-likelihood (GQL) approach and a generalized method of moments (GMM) approach. These are alternative approaches to the typical maximum-likelihood approximation approach in Statistical Analysis System (SAS) such as Laplace approximation (LAP). We examined and compared the performance of GQL and GMM approaches with multiple random effects to the LAP approach as used in PROC GLIMMIX, SAS. The GQL approach tends to produce unbiased estimates, whereas the LAP approach can lead to highly biased estimates for certain scenarios. The GQL approach produces more accurate estimates on both the regression coefficients and the covariance parameters with smaller standard errors as compared to the GMM approach. We found that both GQL and GMM approaches are less likely to result in non-convergence as opposed to the LAP approach. A simulation study was conducted and a numerical example was presented for illustrative purposes.