The Copula Approach to Sample Selection Modelling: An Application to the Recreational Value of Forests

The sample selection model is based upon a bivariate or a multivariate structure, and distributional assumptions are in this context more severe than in univariate settings, due to the limited availability of tractable multivariate distributions. While the standard FIML estimation of the selectivity model assumes normality of the joint distribution, alternative approaches require less stringent distributional hypotheses. As shown by Smith (2003), copulas allow great flexibility also in FIML models. The copula model is very useful in situations where the applied researcher has a prior on the distributional form of the margins, since it allows separating their modelling from that of the dependence structure. In the present paper the copula approach to sample selection is first compared to the semiparametric approach and to the standard FIML, bivariate normal model, in an illustrative application on female work data. Then its performance is analysed more thoroughly in an application to Contingent Valuation data on recreational values of forests.Contingent valuation, Selectivity bias, Bivariate models, Copulas

The C242T polymorphism of the NAD(P)H oxidase p22(phox) subunit is associated with an enhanced risk for cerebrovascular disease at a young age

Background and Purpose: Oxidative stress has been proposed as a major contributing factor for vascular disease, that acts independently from its participation in predisposing disorders such as diabetes and arterial hypertension. A functionally relevant C242T polymorphism of the CYBA gene encoding the NAD(P)H oxidase p22(phox) subunit, is supposed to lead to an abnormal reduction in the generation of reactive oxygen species in vascular smooth-muscle and endothelial cells. Methods: We investigated the p22(phox) C242T single-nucleotide polymorphism by polymerase chain reaction in consecutive patients with ischemic stroke or transient ischemic attack under the age of 50 (n = 161) and in population-based control subjects (n = 136). Results: Homozygosity for the T variant was associated with an enhanced risk for cerebral ischemia (odds ratio 3.85, confidence interval 1.39-10.64) after adjusting for classical risk factors. Risk for cerebral ischemia was not increased in heterozygous subjects. Conclusion: The p22(phox) C242T single-nucleotide polymorphism is associated with stroke risk. This finding supports the hypothesis that oxidative stress may contribute to stroke pathogenesis. Copyright (C) 2008 S. Karger AG, Basel

Productivity Growth and Efficiency under Leontief Technology: An Application to US Steam-Electric Power Generation Utilities

A theoretical framework is developed for decomposing partial factor productivity and measuring technical inefficiency when the underlying technology is characterized by factor non-substitution. With Farrell's (1957) radial index of technical inefficiency being inappropriate in this case, Russell's (1985; 1987) non-radial indices are adapted to measure technical inefficiency in a Leontief model. A system of factor demand equations with a regime specific technical inefficiency term is proposed and estimated allowing for dependence across inputs using a copula approach. Then the paper presents a complete decomposition of partial factor productivity changes using a dataset of U.S. steam-power electric generation utilities.

ASSESSING EUROPEAN FARMERS’ INTENTIONS IN THE LIGHT OF THE 2003 CAP REFORM

The effects of the 2003 CAP reform on the farmers’ decisions on whether to abandon their farming activity, how much to produce and what to produce are analyzed in the present paper. To this effect data collected for Hungarian, Dutch and Greek farmers on their perceptions about the reform and its effects, and on their production intentions is analyzed using discrete choice models under 3 alternative scenarios for the future produce prices. The discrete choice model applied in the present paper is sequential since farmers are confronted with a sequence of choices. In the first stage, the choice is between abandoning farming or continuing, then those farmers who have chosen to continue are presented with two additional choices related to their level of production and crop mix. Some of the results of the analysis point out that the evolution of future prices, level of information about Cap reform, farm size play an important role in the decision to abandon or continue. In the case of Hungary and Greece, younger farmers are less likely to abandon, more likely to increase production and change crop mix than their older counterparts, emphasizing the importance of aids to the young.CAP, Farmers choices, MTR assesment, Agricultural and Food Policy, Political Economy, Q10, Q18,

The Demand for Organic, Integrated-Agriculture, and Conventional Fresh Vegetables: A Censored Inverse Almost Ideal Demand System

The Inverse Almost Ideal Demand System is employed for the empirical analysis of the demand for organic, integrated-agriculture, and conventional fresh vegetables, using a cross section data surveyed in Rethymno, Greece during the 2005-06 period. The demand system is estimated by employing the Amemiya-Tobin model by Wales and Woodland for the estimation of censored equation systems, which ensures that the adding-up restriction is satisfied for both the latent and the observed expenditure shares. The problem regarding the logarithm of quantities when zero purchases are reported, is resolved in a theoretically consistent way that allows full-sample estimation and yields unbiased parameter estimates. The empirical results suggest that integrated-agriculture fresh vegetables are luxury goods, whereas the cross-quantity uncompensated flexibilities indicate that consumers are not regular buyers of any of the three types of fresh vegetables. Both groups of consumers who currently buy integrated-agriculture vegetables and those who buy conventional vegetables can be easily induced to buy organic vegetables.

Information Acquisition and Adoption of Organic Farming Practices: Evidence from Farm Operations in Crete, Greece

The objective of the paper is to model the degree of organic farming adoption as well as the importance of technical information acquisition in the adoption decision process. In doing so, a trivariate ordered probit model is specified and implemented in the case of organic farming adoption in Crete, Greece. The results suggest that the decisions of information acquisition and adoption are indeed correlated and different farming information sources play a complementary role. Policies required to encourage organic farming adoption should be primarily structural while the provision of technical information is more crucial than conversion subsidies if total organic adoption is to be pursued.Technology adoption, information acquisition, organic farming, Crete, Greece

Heritage, politics and identity : exploring the political manipulation of heritage in Zimbabwe

A research report submitted to the Faculty of Humanities, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Arts in the field of Heritage StudiesPostcolonial Zimbabwe is currently in an era characterised by discursive contestations. This has seen the ruling party, ZANU PF, engaging in severe discourse manipulation in a bid to gain political legitimacy. This new era has resulted in the emergence of what Ranger (2004) has termed ‘patriotic history’, which is a new form of narrow history, which is biased towards celebrating an exaggerated role played by ZANU PF in liberating Zimbabwe, portraying the ruling party as the only truly legitimate rulers of post-independence Zimbabwe. This study, therefore,seeks to examine recent discourse on ZANU PF’s ideology, and to explore how this master narrative has been used to justify ZANU PF’s unpopular projects, such as the land reform programme, and the establishment of the National Youth Service ,popularly known as ‘Border Gezi youth camps’

Information Acquisition and Adoption of Organic Farming Practices

This study offers an empirical framework for analyzing farmers' joint decisions to adopt organic farming practices and to seek technical (i.e., farming) information from various sources. To that end, a trivariate ordered probit model is specified and implemented in the case of organic land conversion in Crete, Greece. Findings suggest that the decisions of information acquisition and organic land conversion are indeed correlated, and different farming information sources play a complementary role. Structural policies improving the farmer's allocative ability are found to play an important role in encouraging organic farming adoption.Crete, Greece, information acquisition, organic farming, technology adoption, Farm Management,

An Exploration of the Correlation Between Body Mass and Skeletal Measurements of the Long Bone Joints and Diaphyses

Body mass is a characteristic of the human body that can aid in narrowing down potential identifications of unidentified individuals. However, when faced with skeletal remains, body mass is not easily ascertained, especially when the remains are incomplete. This research explores the potential correlation between body mass and long bone dimensions in order to aid in identification efforts. The limited research done prior has been conducted almost exclusively on the lower limbs—therefore, one of the primary foci of this study is to assess the efficacy of using the joint surfaces and shaft measurements of the upper limbs. Five long bones (humerus, radius, ulna, tibia, and femur) were measured across a sample size of 20 males of varying body mass from the William M. Bass Skeletal Collection at the University of Tennessee Knoxville. Fifty-one measurements assessing joint surface area as well as shaft diameters were taken directly from the remains, while three more were extracted from the existing data. Descriptive analysis showed promising results for a potential correlation between body mass and certain measurements of the long bones. The significant correlations were largely evenly distributed among the articular and diaphyseal surfaces. The lower limb, especially the shaft diameters, was found to be more highly correlated with body mass values. The upper limb, however, showed much more limited potential for estimating body mass, likely since it is not directly involved in carrying weight. These findings have implications for further studies with larger sample sizes