Approximate jackknife empirical likelihood method for estimating equations

It is known that the profile empirical likelihood method based on estimating equations is computationally intensive when the number of nuisance parameters is large. Recently, Li, Peng, & Qi (2011) proposed a jackknife empirical likelihood method for constructing confidence regions for the parameters of interest by estimating the nuisance parameters separately. However, when the estimators for the nuisance parameters have no explicit formula, the computation of the jackknife empirical likelihood method is still intensive. In this paper, an approximate jackknife empirical likelihood method is proposed to reduce the computation in the jackknife empirical likelihood method when the nuisance parameters cannot be estimated explicitly. A simulation study confirms the advantage of the new method. The Canadian Journal of Statistics 40: 110–123; 2012 © 2012 Statistical Society of Canada     

Restricted maximum likelihood estimation of joint mean‐covariance models

The class of joint mean‐covariance models uses the modified Cholesky decomposition of the within subject covariance matrix in order to arrive to an unconstrained, statistically meaningful reparameterisation. The new parameterisation of the covariance matrix has two sets of parameters that separately describe the variances and correlations. Thus, with the mean or regression parameters, these models have three sets of distinct parameters. In order to alleviate the problem of inefficient estimation and downward bias in the variance estimates, inherent in the maximum likelihood estimation procedure, the usual REML estimation procedure adjusts for the degrees of freedom lost due to the estimation of the mean parameters. Because of the parameterisation of the joint mean covariance models, it is possible to adapt the usual REML procedure in order to estimate the variance (correlation) parameters by taking into account the degrees of freedom lost by the estimation of both the mean and correlation (variance) parameters. To this end, here we propose adjustments to the estimation procedures based on the modified and adjusted profile likelihoods. The methods are illustrated by an application to a real data set and simulation studies. The Canadian Journal of Statistics 40: 225–242; 2012 © 2012 Statistical Society of Canada     

Reimagining the General Health Questionnaire as a measure of emotional wellbeing: A study of postpartum women in Malta

BackgroundPostpartum health has been subject to a focus on psychological morbidity, despite positive associations between postpartum recovery and maternal emotional wellbeing. There are currently many validated tools to measure wellbeing and related concepts, including non-psychiatric morbidity. The General Health Questionnaire, 12 items (GHQ-12) is one such instrument, widely used and validated in several languages. Its use in postpartum settings has been documented with disagreement about the instrument's utility in this population, particularly in relation to scoring method and threshold. The GHQ-12 has never been translated into Maltese. This study explored the psychometric properties of the GHQ-12 in a Maltese postpartum population to consider if the use of a different scoring method (visual analogue scale) in the GHQ-12 can determine postpartum wellbeing.MethodsOne hundred and twenty-four postpartum women recruited from one hospital in Malta completed the translated and adapted GHQ-12 as a wellbeing measure (GHQ-12(WB)) at four postpartum time points. The psychometric properties of the GHQ-12(WB) were explored using confirmatory factor analysis, discriminant and divergent validity and reliability analysis.ResultsThe GHQ-12(WB) demonstrated good divergent and known-groups validity and internal consistency. No models offered a good fit to the data. The overall consistent best-fit to the data was an eight item, two factor model (GHQ-8). Model fit improved across all models in terms of CFI at 13 weeks.ConclusionFindings generally support the reliability and validity of the Maltese version of the GHQ-12(WB). Model fit changes over time reflect the dynamic nature of postpartum recovery. Further evaluation of the GHQ-8(WB) is recommended.     

Return and volatility interaction between oil prices and stock markets in Saudi Arabia

The paper aims at investigating the links between world oil price and stock sector markets in Saudi Arabia over the weekly period from January 10, 2007 until September 28, 2011. To that effect, we make use of the VAR-GARCH process developed by Ling and McAleer (2003), which has the advantage to address the issue of return and volatility spillovers among the series we consider. Globally, the empirical findings show evidence of return and volatility transmission between oil price and stock sectors. However, the spillover effects are unidirectional from oil to some sectors for returns, but bidirectional for volatility patterns with more apparent links from sectors to oil. The optimal weights and hedge ratios for oil/stock portfolio holdings are sensitive to the sectors considered, and allow a better understanding of the links between sectors and oil for investors who seek for investment opportunities and want to diversify their portfolios. The findings are of great interest and have important implications for investors, market participants and policy makers.     

Food subsidy,income transfer and the poor: A comparative analysis of the public distribution system in India's states

The Targeted Public Distribution System (TPDS) – the largest food subsidy program in India – has been a dismal failure in targeting the poor. The present paper examines its performance in three Indian states – Andhra Pradesh, Maharashtra and Rajasthan, based on primary data collected for this study. As real income transfers through food price subsidies are a tiny fraction of expenditure per person under this scheme, a contribution of the present study is to model determinants of real income transfers through subsidised wheat, rice and sugar. The analysis throws new light on how income transfers vary with economic status of a household, inequality in the distribution of land in a village, amount of food price subsidy, transaction costs of buying from ‘fair price shops’ (FPS), and supply shortages. The policy implications of these results are profound. Desperate measures such as a universal food subsidy enshrined in a proposed National Food Security Act are rejected on the grounds that the enormous leakages and wastage under the present TPDS would only get worse. Assertions that a universal food subsidy is the only option consistent with the right to food are rejected as mistaken. Instead, it is worthwhile to overhaul the PDS within the existing outlay.     

Kind of Black: The Musicians' Labour Market in Italy

It is estimated that only 5 per cent of musicians in Italy are regularly employed. In an attempt at understanding such a peculiar situation, we build a theoretical model of the musicians' labour market in which we embed the main institutional features of the Italian system. The presence of taxation encourages the formation of a black labour market for musicians and discourages talented agents from becoming full‐time musicians in all second‐best economies. In Italy both tendencies are particularly strong, and exacerbated by the peculiarities of the pension system for musicians. These inefficiencies might be corrected by a twofold policy: the reform of the pension system, highly desirable but unlikely to be politically feasible in the current Italian institutional setting, and the introduction of a sufficiently large unemployment benefit for musicians, step that has a general interest for any second‐best economy and not only for the case of the musicians' labour market, and that might instead be viable under certain circumstances.     

THE RELATIONSHIP BETWEEN CHILD HEALTH,DEVELOPMENTAL GAPS,AND PARENTAL EDUCATION: EVIDENCE FROM ADMINISTRATIVE DATA

We use administrative German data to examine the role of physical and mental health conditions in explaining developmental gaps between children whose parents have different educational levels. Specifically, we employ sibling fixed effect models to estimate the effect of a comprehensive list of childhood health conditions—diagnosed by government physicians—on the cognitive and verbal ability of pre‐school children. We also apply decomposition methods to examine the extent to which gaps in child development can be attributed to child health conditions. While most physical health conditions have small and insignificant effects, mental health conditions, in particular hyperactivity, have a large and significant effect on development. Mental health conditions account for 14%–36% of the gap in cognitive ability and for 23%–24% of that in verbal ability. Thus, policies aimed at reducing disparities in child development and socioeconomic inequalities later in life should focus more on the early diagnosis and effective treatment of mental health conditions.     

ROUTES OF INFECTION: EXPORTS AND HIV INCIDENCE IN SUB‐SAHARAN AFRICA

This paper estimates whether exports affect the incidence of HIV in Africa. This relationship has implications for HIV prevention policy as well as for the consequences of trade increases in Africa. I estimate this impact using two sources of data on HIV incidence, one generated based on UNAIDS estimates and the other based on observed HIV mortality. These data are combined with data on export value and volume. I find a fairly consistent positive relationship between exports and new HIV infections: doubling exports leads to a 10%–70% increase in new HIV infections. Consistent with theory, this relationship is larger in areas with higher baseline HIV prevalence. I interpret the result as suggesting that increased exports increase the movement of people (trucking), which increases sexual contacts. Consistent with this interpretation, the effect is larger for export growth than for income growth per se and is larger in areas with more extensive road networks.     

Joint decisions on household membership and human capital accumulation of youths. The role of expected earnings and local markets

This paper analyses the effects of expected earnings and local markets conditions on the behaviour of young adults with high school diplomas. Decisions to either remain in the parental home or form a new household are modelled jointly with those of either gaining work experience or investing in a university education. Expected lifetime earnings are found to play a crucial role in determining the choice of studying and residing with parents. Poor labour market opportunities discourage young people from working and induce them to study. The cost of housing greatly influences the choice of working and leaving the parental home. Received: 23 March 2001/Accepted: 26 November 2001 All correspondence to Gianna Claudia Giannelli. Helpful comments by two anonymous referees are gratefully acknowledged. Responsible editor: John F. Ermisch.     

TRADE QUOTAS AND BUYER POWER,WITH AN APPLICATION TO THE E.U. NATURAL GAS MARKET

We consider a market in which domestic buyers negotiate contracts with foreign sellers, and explore how trade quotas can help to increase the buyers' countervailing power. We use the Shapley value to describe bargaining power and the distribution of the trade surplus in such a bilateral oligopoly. By exploiting strategic externalities among the buyers, bilateral trade quotas can improve the buyers' bargaining positions. In contrast, aggregate trade restrictions on all buyers' trade never improve buyer surplus. Minimum quotas on imports from fringe suppliers can benefit nonaffected buyers, as these enjoy positive externalities. We apply these insights to the E.U. market for natural gas and show that the effects of trade quotas on E.U. gas importers' power can be significant.