Preferences, common knowledge and speculative trade

We study the proposition that if it is common knowledge that en allocation of assets is ex-ante pareto efficient, there is no further trade generated by new information. The key to this result is that the information partitions and other characteristics of the agents must be common knowledge and that contracts, or asset markets, must be complete. It does not depend on learning, on 'lemons' problems, nor on agreement regarding beliefs and the interpretation of information. The only requirement on preferences is state-additivity; in particular, traders need not be risk-averse. We also prove the converse result that "no-trade results" imply that traders' preferences can be represented by state-additive utility functions. We analyze why examples of other widely studied preferences (e.g., Schmeidler (1989)) allow "speculative" trade.

Normality under uncertainty

Consider the demand for a good whose consumption be chosen prior to the resolution of uncertainty regarding income. How do changes in the distribution of income affect the demand for this good? In this paper we show that normality, is sufficient to guarantee that consumption increases of the Radon-Nikodym derivative of the new distribution with respect to the old is non-decreasing in the whole domain. However, if only first order stochastic dominance is assumed more structure must be imposed on preferences to guanantee the validity of the result. Finally a converse of the first result also obtains. If the change in measure is characterized by non-decreasing Radon-Nicodyn derivative, consumption of such a good will always increase if and only if the good is normal.

The consistency of welfare judgements with a representative consumer

This paper is about economies with a representative consumer. In general a representative consumer need not exist, although there are several well known sets of sufficient conditions under which Qne will. It is common practice, however, to use the representative consumer hypothesis without specifically assuming any of these. We show, firstly, that it is possible for the utility of the representative consumer to increase when every actual consumer is made worse off. This shows a serious shortcoming of welfare judgements based on the representatíve consumer. Secondly, in economies where this does not occur, there exists a social welfare function, which we construct, which is consistent with welfare judgements based on the utility of the representative consumer. Finally we provide a converse to Samuelson' s 1956 representative consumer result, which relates it to Scitovsky's community indifference curves.

On the consistency of arbitrary money-demand functions with the Sidrauski and the shopping-time models

This paper investigates which properties money-demand functions have to satisfy to be consistent with multidimensional extensions of Lucasí(2000) versions of the Sidrauski (1967) and the shopping-time models. We also investigate how such classes of models relate to each other regarding the rationalization of money demands. We conclude that money demand functions rationalizable by the shoppingtime model are always rationalizable by the Sidrauski model, but that the converse is not true. The log-log money demand with an interest-rate elasticity greater than or equal to one and the semi-log money demand are counterexamples.

Sincretização do controle de constitucionalidade no ordenamento jurídico brasileiro: abstratização do controle difuso e concretização do controle abstrato

Considerando-se as recentes decisões do Supremo Tribunal Federal no controle de constitucionalidade, percebe-se o movimento de sincretização entre os controles abstrato e concreto. A visão da atual jurisdição constitucional revela que as últimas criações legislativas foram inseridas no controle abstrato, sendo o caminho utilizado para resolução das principais controvérsias judiciais, com seus efeitos erga omnes e vinculantes. Esse panorama não afastou a utilização do controle concreto, que se renova ao se aproveitar dos instrumentos do controle concentrado abstrato. Não apenas o controle concreto e difuso está se beneficiando do controle abstrato, como também a recíproca é verdadeira. O controle abstrato também se beneficia ao valer-se de diversos instrumentos que não seriam possíveis por suas características abstratas. O objetivo do presente trabalho é analisar esse movimento, através de casos emblemáticos e instrumentos criados pelas Leis que tratam sobre o controle de constitucionalidade, a fim de comprovar esse novo cenário na ordem jurídica brasileira. Este trabalho foi realizado através de pesquisas bibliográficas e casos perante o Supremo Tribunal Federal. O resultado da análise comprova essa tendência na utilização de pressupostos que seriam apenas de um controle, sendo utilizado pelo outro. Isso representa um grande avanço para o tema controle de constitucionalidade que tende cada vez mais a ser sincretizado.

Collateral or utility penalties ?

In a two-period economy with incomplete markets and possibility of default we consider the two classical ways to enforce the honor of financial commitments: by using utility penalties and by using collateral requirements that borrowers have to fulfill. Firstly, we prove that any equilibrium in an economy with collateral requirements is also equilibrium in a non-collateralized economy where each agent is penalized (rewarded) in his utility if his delivery rate is lower (greater) than the payment rate of the financial market. Secondly, we prove the converse: any equilibrium in an economy with utility penalties is also equilibrium in a collateralized economy. For this to be true the payoff function and initial endowments of the agents must be modified in a quite natural way. Finally, we prove that the equilibrium in the economy with collateral requirements attains the same welfare as in the new economy with utility penalties.