Are CGE Models still useful in economic policy making?

This paper develops background considerations to help better framing the results of a CGE exercise. Three main criticisms are usually addressed to CGE efforts. First, they are too aggregate, their conclusions failing to shed light on relevant sectors or issues. Second, they imply huge data requirements. Timeliness is frequently jeopardised by out-dated sources, benchmarks referring to realities gone by. Finally, results are meaningless, as they answer wrong or ill-posed questions. Modelling demands end up by creating a rather artificial context, where the original questions lose content. In spite of a positive outlook on the first two, crucial questions lie in the third point. After elaborating such questions, and trying to answer some, the text argues that CGE models can come closer to reality. If their use is still scarce to give way to a fruitful symbiosis between negotiations and simulation results, they remain the only available technique providing a global, inter-related way of capturing economy-wide effects of several different policies. International organisations can play a major role supporting and encouraging improvements. They are also uniquely positioned to enhance information and data sharing, as well as putting people from various origins together, to share their experiences. A serious and complex homework is however required, to correct, at least, the most dangerous present shortcomings of the technique.

O desenvolvimento do conceito de probabilidade em pré-adolescentes e adolescentes

Este trabalho, baseado na teoria de Jean Piaget sobre o desenvolvimento do pensamento adolescente, visa continuar a mesma linha de investigação no que se refere à aquisição do conceito de probabilidade. O conceito de probabilidade na teoria piagetiana representando a intercepção do real e do possível, foi submetido, neste trabalho, a uma análise crítica e a um projeto de verificação experimental. Em termos teóricos, a crítica orientou-se para a relação entre os canais sensoriais receptores de informação e a organização do nível formal que permite elaborar relações de probabilidade. Importante papel foi atribuído ao estudo da manipulação - expressão direta da ação em seus níveis primordiais - como fator determinante de elaboração específica nas relações de probabilidade. Uma segunda vertente sociogênica do problema foi analisada em termos do nível sócio-econômico como fator que influencia o desenvolvimento do pensamento formal e especificamente a aquisição do conceito de probabilidade. Em termos de verificação experimental, constatou se a possibilidade de se definirem diversos estágios de desenvolvimento, chegando-se a classificar, de modo geral, os sujeitos em: aqueles que ainda não possuem habilidade de pensamento para solução de problema de probabilidade, aqueles que já apresentam tal habilidade, porém, são incapazes de generalização, e outros, em menor parte, que têm estabelecidas as estruturas operatórias do período lógico formal. Dentre estes grupos somente o último faz uso sistemático de estratégias corretas e corresponde aos sujeitos adolescentes do sexo masculino. Isto mostra que existe uma diferença nos resultados devido às diferenças sexuais a favor do sexo masculino e que a capacidade de lidar com relações probabilísticas se torna mais organizada e estruturada com o avanço da idade dos sujeitos. As variáveis ambientais exercem influência no rendimento do sujeito, os resultados variam de acordo com o meio socio econômico, favorecendo os de nível superior, isto é, permitindo-lhes um desenvolvimento normal.

Integrability and the demand for monetary assets: an alternative approach to an old problem

This note provides necessary and su¢cient conditions for some speci…c multidimensional consumer’s surplus welfare measures to be well posed (path independent). We motivate the problem by investigating partial-equilibrium measures of the welfare costs of in‡ation. The results can also be used for checking path independence of alternative de…nitions of Divisia indexes of monetary services. Consumer theory classically approaches the integrability problem by considering compensated demands, homothetic preferences or quasi-linear utility functions. Here, instead, we consider demands of monetary assets generated from a shopping-time perspective. Paralleling the above mentioned procedure, of …nding special classes of utility functions that satisfy the integrability conditions, we try to infer what particular properties of the transacting technology could assure path independence of multidimensional welfare measures. We show that the integrability conditions are satis…ed if and only if the transacting technology is blockwise weakly separable. We use two examples to clarify the point.

Global stabilizing feedback law for a problem of biological control of mosquito-borne diseases

The control of the spread of dengue fever by introduction of the intracellular parasitic bacterium Wolbachia in populations of the vector Aedes aegypti, is presently one of the most promising tools for eliminating dengue, in the absence of an efficient vaccine. The success of this operation requires locally careful planning to determine the adequate number of mosquitoes carrying the Wolbachia parasite that need to be introduced into the natural population. The latter are expected to eventually replace the Wolbachia-free population and guarantee permanent protection against the transmission of dengue to human. In this paper, we propose and analyze a model describing the fundamental aspects of the competition between mosquitoes carrying Wolbachia and mosquitoes free of the parasite. We then introduce a simple feedback control law to synthesize an introduction protocol, and prove that the population is guaranteed to converge to a stable equilibrium where the totality of mosquitoes carry Wolbachia. The techniques are based on the theory of monotone control systems, as developed after Angeli and Sontag. Due to bistability, the considered input-output system has multivalued static characteristics, but the existing results are unable to prove almost-global stabilization, and ad hoc analysis has to be conducted.