 Economics  Research Publications
Economics  Research Publications
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ItemEstimation and efficiency measurement in stochastic production frontiers with ordinal outcomesGriffiths, W ; Zhang, X ; Zhao, X (SPRINGER, 201408)We consider Bayesian estimation of a stochastic production frontier with ordered categorical output, where the inefficiency error is assumed to follow an exponential distribution, and where output, conditional on the inefficiency error, is modelled as an ordered probit model. Gibbs sampling algorithms are provided for estimation with both crosssectional and panel data, with panel data being our main focus. A Monte Carlo study and a comparison of results from an example where data are used in both continuous and categorical form supports the usefulness of the approach. New efficiency measures are suggested to overcome a lackofinvariance problem suffered by traditional efficiency measures. Potential applications include health and happiness production, university research output, financial credit ratings, and agricultural output recorded in broad bands. In our application to individual health production we use data from an Australian panel survey to compute posterior densities for marginal effects, outcome probabilities, and a number of withinsample and outofsample efficiency measures.

ItemBayesian inference for health inequality and welfare using qualitative dataGunawan, D ; Griffiths, WE ; Chotikapanich, D (ELSEVIER SCIENCE SA, 20180101)We show how to use Bayesian inference to compare two ordinal categorical distributions commonly occurring with data on selfreported health status. Procedures for computing probabilities for first and second order stochastic dominance and Sdominance are described, along with methodology for obtaining posterior densities for health inequality indexes. The techniques are applied to four years of data on Australian selfreported health status.

ItemUsing the GB2 Income DistributionChotikapanich, D ; Griffiths, WE ; Hajargasht, G ; Karunarathne, W ; Rao, DSP (MDPI AG, 20180601)To use the generalized beta distribution of the second kind (GB2) for the analysis of income and other positively skewed distributions, knowledge of estimation methods and the ability to compute quantities of interest from the estimated parameters are required. We review estimation methodology that has appeared in the literature, and summarize expressions for inequality, poverty, and propoor growth that can be used to compute these measures from GB2 parameter estimates. An application to data from China and Indonesia is provided.

ItemEstimation and testing of stochastic frontier models using variational BayesHajargasht, G ; Griffiths, WE (Springer Verlag, 201810)We show how a wide range of stochastic frontier models can be estimated relatively easily using variational Bayes. We derive approximate posterior distributions and point estimates for parameters and inefficiency effects for (a) time invariant models with several alternative inefficiency distributions, (b) models with time varying effects, (c) models incorporating environmental effects, and (d) models with more flexible forms for the regression function and error terms. Despite the abundance of stochastic frontier models, there have been few attempts to test the various models against each other, probably due to the difficulty of performing such tests. One advantage of the variational Bayes approximation is that it facilitates the computation of marginal likelihoods that can be used to compare models. We apply this idea to test stochastic frontier models with different inefficiency distributions. Estimation and testing is illustrated using three examples.

ItemSome models for stochastic frontiers with endogeneityGriffiths, WE ; Hajargasht, G (ELSEVIER SCIENCE SA, 201602)

ItemOn GMM estimation of distributions from grouped dataGriffiths, W ; Hajargasht, G (Elsevier, 2015)For estimating distributions from grouped data, setting up moment conditions in terms of group shares and group means leads to an optimal weight matrix and a GMM objective function that are considerably simpler than those from a previous specification. Minimization is more efficient and convergence is more reliable.

ItemGlobal Inequality; Levels and Trends, 1993–2005: How Sensitive are These to the Choice of PPPs and Real Income Measures?Warner, D ; Rao, DSP ; Griffiths, WE ; Chotikapanich, D (Wiley, 20141101)Increasing global interaction between economies over the last few decades has led to growing interest on the implications of globalization. Of particular interest has been the distributional impact of globalization and whether this has been equity enhancing. Contributing to this debate, Chotikapanich et al. have previously estimated global and regional inequalities for 1993 and 2000. The current paper presents estimates of global inequality for 2005, making use of purchasing power parity (PPP) data from the 2005 International Comparison Program (ICP) round. A critical element in the estimation of regional and global inequality is the data on PPPs and real incomes. Another objective of the paper is to examine the sensitivity of the inequality results to the use of alternative sets of real incomes using different sets of PPP data to convert per capita income data into a common currency unit. The paper also compares levels and trends of global inequality measures based on real per capita income measures from the national accounts and those obtained using per capita expenditure data from household expenditure surveys. The main finding of the paper is that the populist view that globalization has increased inequality does not hold when inequality is measured at the global level. Between 1993 and 2005, inequality has consistently declined as measured both by the Gini coefficient and the Theil index. This decline in global inequality was the result of a decline in inequality between countries. The estimates do suggest that there is an overall upward trend in inequality within countries, lending some support for protestors against globalization. Another finding is that the levels of global inequality are indeed sensitive to the choice of PPPs. However, the downward trend in global inequality is consistently evident across different choices of PPPs and real incomes. We find similar trends in inequality and in the within and between components of inequality when inequality measures are based on national accounts real per capita incomes or on the surveybased real per capita expenditures.

ItemGibbs samplers for a set of seemingly unrelated regressionsGriffiths, W. E. ; Valenzuela, Ma. Rebecca ( 200408)Bayesian estimation of a collection of seemingly unrelated regressions, referred to asa ‘set of seemingly unrelated regressions’ is considered. The collection of seeminglyunrelated regressions is linked by common coefficients and/or a common errorcovariance matrix. Gibbs samplers useful for estimating posterior quantities aredescribed and applied to two examples – a set of linear expenditure functions and acost function and share equations from production theory.

ItemEstimating and Combining National IncomeDistributions using Limited DataChotikapanich, Duangkamon ; Griffiths, William E. ; Rao, D. S. Prasada ( 200502)A major problem encountered in studies of income inequality at regional and globallevels is the estimation of income distributions from data that are in a summary form.In this paper we estimate national and regional income distributions within a generalframework that relaxes the assumption of constant income within groups. A techniqueto estimate the parameters of a beta2 distribution using grouped data is proposed.Regional income distribution is modelled using a mixture of countryspecificdistributions and its properties are examined. The techniques are used to analysenational and regional inequality trends for eight East Asian countries and twobenchmark years, 1988 and 1993.

ItemSurvival on the Titantic: Illustrating Waldand LM Tests for Proportions and LogitsDIXON, ROBERT ; GRIFFITHS, WILLIAM ( 200606)Students are very interested in lecture examples and class exercisesinvolving data connected to the maiden voyage and the sinking of the liner Titanic.Information on the passengers and their fate can be used to explore relationshipsbetween various tests for differences in survival rates between different groups ofpassengers. Among the concepts examined are tests for differences of proportionsusing a normal distribution, a chisquare test for independence, a test for the equalityof two logits and a test for the significance of the coefficient of a binary variable inlogit model. The relationship between Wald and LM test statistics is also examined.Two related examples are given, one to be used for step by step instructional purposesand one to be given as an exercise to students.