Generalized least squares with misspecified serial correlation structures

Summary. The regression literature contains hundreds of studies on serially correlated disturbances. Most of these studies assume that the structure of the error covariance matrix Ω is known or can be estimated consistently from data. Surprisingly, few studies investigate the properties of estimated generalized least squares (GLS) procedures when the structure of Ω is incorrectly identified and the parameters are inefficiently estimated. We compare the finite sample efficiencies of ordinary least squares (OLS), GLS and incorrect GLS (IGLS) estimators. We also prove new theorems establishing theoretical efficiency bounds for IGLS relative to GLS and OLS. Results from an exhaustive simulation study are used to evaluate the finite sample performance and to demonstrate the robustness of IGLS estimates vis-à-vis OLS and GLS estimates constructed for models with known and estimated (but correctly identified) Ω. Some of our conclusions for finite samples differ from established asymptotic results.     

Efficient Semiparametric Estimation of Quantile Treatment Effects

This paper develops estimators for quantile treatment effects under the identifying restriction that selection to treatment is based on observable characteristics. Identification is achieved without requiring computation of the conditional quantiles of the potential outcomes. Instead, the identification results for the marginal quantiles lead to an estimation procedure for the quantile treatment effect parameters that has two steps: nonparametric estimation of the propensity score and computation of the difference between the solutions of two separate minimization problems. Root‐N consistency, asymptotic normality, and achievement of the semiparametric efficiency bound are shown for that estimator. A consistent estimation procedure for the variance is also presented. Finally, the method developed here is applied to evaluation of a job training program and to a Monte Carlo exercise. Results from the empirical application indicate that the method works relatively well even for a data set with limited overlap between treated and controls in the support of covariates. The Monte Carlo study shows that, for a relatively small sample size, the method produces estimates with good precision and low bias, especially for middle quantiles.     

Patterns of american jewish fertility

The 1971 National Jewish Population Survey provides cross-sectional data on achieved fertility, detailed birth histories, and other information on family formation for a countrywide representative sample of 5,303 ever-married women. Cohort analysis shows that—although at lower levels—Jewish fertility has followed the general trends of American population.     

Ergonomics in designing process: dialogue between designers, executors and users in the maintenance activity of radars in an oil refinery

This paper aims to discuss the role of ergonomics in design process using the dialogue developed by designers, implementers and users in an oil refinery. It was possible to identify the need of minimizing the postural constraints, risk of accidents, mechanical shocks and to enlarge safety perception in the access and permanency of the users at the workspace. It has been determined and validated by workers and managers to implement different deadlines depending on programming, viability and execution time for the improvements proposed. In a long-term: it was proposed the substitution of the ladders with time planning according to the maintenance program of the tanks; in a short-time: it was suggested the expansion of the existing platforms, implementation of a walkway connection provided with guardrails between the upper access of the side ladder and the repositioning of radar set and aerial aiming at the usage by workers at the workstation of the new platform. It was also elaborated eight typologies of intervention, according to the request, type of tank, material stored, and its setting place. The design process arises from ergonomics workplace analysis that presents concepts for solutions which was a mediator tool to be settled between users and implementers.     

Efficiency of personal protective equipment used in agriculture

Despite the practical importance of Personal Protective Equipment (PPE), both in production and in consumption, it is observed a main problem regarding the quality of many PPE?s used in Brazil. This study found a gap between the state of the art and the state of prevailing practices in the design of PPE?s, which main consequences affect the health of workers who use PPE in agriculture activities. The results of this study identified legal constraints of this occurrence, involving the validation of PPE designed for isolate agents, without the analysis of relevant activities and without prototypes experiments in more frequent use situation.     

The footwear factory's assembly sector: opposing organizational structure and quality from the ergonomic work analysis

Data from 2006 indicated that Brazilian footwear leather industry was composed of approximately 9,488 formally registered establishments, considering the leather industry, footwear and leather goods. It was responsible for 211,582 people employed. However, in spite of having many employees, this kind of organization found several problems when analyzed from the ergonomics view. With this premise, then, in order to identify bottlenecks and other engineering problems that could cause discomfort and motivation lack among workers, leading directly to the loss of the product quality, the assembly sector of women's shoes factory was characterized.     

Life on the Edge: Balancing Gendered and Occupational Identities among Unauthorized Mexican Migrant Roofers

Scholars have addressed the economic, gendered, and emotional dimensions of migration, especially as migrants move from origin to destination. However, scholarship on return migration and the subjective experiences of reintegrating to origin communities is poorly understood. In this paper, we examine the return migration of formerly unauthorized migrants who labored as roofers in the United States. We argue that the migration process redefines men’s masculinity as they attempt to balance family life in Mexico and their occupational lives in the U.S., all of which are essential for their identity but remain separated by an international border. We draw on 40 in-depth interviews with return migrant men in a small city in Guanajuato, Mexico to examine the emotional tensions men experience regarding the decision to remain in close proximity to family in Mexico and a desire to return again to their economically and emotionally fulfilling occupations in the U.S. We find that migrants’ nostalgia for prior U.S. labor market experience, in juxtaposition to reentry into the Mexican labor market, competes with current feelings of happiness and contentment obtained through family reintegration. These competing feelings, together with economic need, help explain the complex meaning of migration for return migrant men. We conclude by suggesting that once men have been exposed to U.S. life, the occupational identity becomes a “pull” that encourages future migration trips.     

A longitudinal perspective on the differentiated valuation of formal education in Brazil in recent decades

The central theme of this article is the relationship between formal education and earnings from a longitudinal perspective, taking into account indicators of social status. Variations in the respective trajectories, in different age cohorts, and in the comparison among different periods are discussed. The empirical material used is based on the microdata files of official statistics. The main techniques put into practice are those that are most focused on measuring the degree of interdependence among variables and those used for means comparison. Our general hypothesis is that the effects of schooling cannot be grasped in terms of education itself but instead in terms of its relationship to status in the social and power structures. One of this paper's principal observations is that of the general declining trend in the economic value of formal education, which varies depending on the level of education and social status. This devaluation is systematic and spans the entire studied universe; however, it focuses much more closely on those of lower social status, particularly for the groups with schooling that is either higher or lower than average.     

Informal Learning for Citizenship Building in Shared Struggles for Rights: Cases of Political Solidarity Between Colombian and Spanish Organisations

Dominant discourses and practices in international cooperation have been characterised by depoliticisation and unequal power relationships. However, a number of more transformative experiences of cooperation also exist, where joint work between Northern and Southern social organisations is linked with a more political perspective. These kinds of experiences can be considered processes of informal learning in social action: through shared actions, strategies and frameworks and through interaction between organisations, institutions and the grassroots, informal and multidimensional learning processes occur in the people and organisations engaged. The study approaches four cases of networks that have linked Spanish and Colombian organisations which promote advocacy and social mobilisation for the defence of human rights in Colombia. The results show that people engaged in the cases experience intense learning processes that are relevant for the construction of solidarities and a radical global citizenship, but that these processes are also replete with limitations, tensions and challenges.     

Measuring cross-country technological catch-up through variable-parameter FDH

In this paper, we estimate indices of technological catch-up for a sample of 52 countries through the FDH approach with variable scaling parameters proposed in Kerstens and Vanden Eeckaut (1999). We show that this technique has significant advantages for the international comparisons of productivity and, more generally, wherever the assumption of convexity for the production set is not likely to be appropriate. We want to thank Laurens Cherchye, Hal Fried, Kristian Kerstens and an anonymous referee for useful comments on preceding versions of this paper. The usual disclaimer applies. Financial support from the MURST, Italy, is gratefully acknowledged.