Toxicity of the systemic insecticide 14 C-phorate and its metabolites to Aphis fabae Scop. (Homoptera: Aphididae)

Imperial Users onl

Estimating fixed-effect panel stochastic frontier models by model transformation

Traditional panel stochastic frontier models do not distinguish between unobserved individual heterogeneity and inefficiency. They thus force all time-invariant individual heterogeneity into the estimated inefficiency. Greene (2005) proposes a true fixed-effect stochastic frontier model which, in theory, may be biased by the incidental parameters problem. The problem usually cannot be dealt with by model transformations owing to the nonlinearity of the stochastic frontier model. In this paper, we propose a class of panel stochastic frontier models which create an exception. We show that first-difference and within-transformation can be analytically performed on this model to remove the fixed individual effects, and thus the estimator is immune to the incidental parameters problem. Consistency of the estimator is obtained by either N→∞ or T→∞, which is an attractive property for empirical researchersStochastic frontier models; Fixed effects; Panel data

A comparative assessment of mortality among the widowers and widows in Taiwan

This paper explores the impact of spousal death on estimated mortality between the widowers and widows among the middle aged and elderly in Taiwan. Subject data is obtained from the Survey of Health and Living Status of the Middle Aged and Elderly in Taiwan, a study conducted in 1996 that encompassed observations 50 years of age and older. Survey data was linked to 1996-2003 national death registry data. Cox proportional hazard model is used to determine the survival rates between the widowers and widows. Main empirical results confirm that the relatively higher mortality hazard associated with being widowhood groups regardless of widowers and widows. Nevertheless, widows face a higher mortality risk than widowers for who compared to their counterparts. In addition, the influences of family and social networks on mortality risk tend to be more important than health status.

Survival Analysis for Unobserved Heterogeneity on Estimated Mortality in Taiwan

The purpose of this study provides evidences on the effects of unobserved heterogeneity on estimated mortality among the middle aged and elderly in Taiwan. The data used is from the Survey of Health and Living Status of the Middle Aged and Elderly in Taiwan (aged 50 to 66), and the mortality information was linked to 1996-2003 national death registry data. The Weibull models are used to estimate the effects of unobserved heterogeneity on mortality. Main empirical results confirm that, after considering unobserved heterogeneity, most estimated coefficients on the mortality regressors are larger in magnitude that the corresponding coefficients in the reference model. Especially, the terms of health care utilization have larger unobserved heterogenity on estimated mortality. Therefore, if the government policies can concern more unobserved heterogenity of health care utilization that might useful to decrease the mortality for the elderly.