Models for which the MLE and the conditional MLE coincide

The MLE, CMLE and MMLE coincide in a linear regression model with fixed individual effects. In this case, there is no incidental parameters problem and the MLE is consistent. The equivalence of these estimators is important because CMLE=MLE implies both the consistency of the MLE and the efficiency of the CMLE. In general, we cannot expect to find a CMLE or MMLE, since there may be no fixed-dimension sufficient statistic for the effects, nor an appropriate transformation of the data whose distribution does not depend on the effects. However, we show that the MLE, CMLE and MMLE do coincide in systems of seemingly unrelated regressions and in systems of simultaneous equations. We establish this result for systems in which (exogenous) variables in addition to (or other than) the intercept may have coefficients which vary over individuals, provided that the set of such variables is the same in every equation.The financial support of the National Science Foundation is gratefully acknowledged.     

Länger leben — Siechtum und Pflege ohne Grenzen?

At present, our society and its social security system are not prepared to cope with the challenges resulting from the continuous increase of life expectancy. The traditional concept of disease has to be modified for serving the special needs of the elderly. The optimistic compression of disease theory is an intriguing model, but lacks prove by available data. The anti-aging boom diverts the focus from the social and financial burden that will be unevitably caused by long-term care in the future. If there will not be an — up to now unforeseeable — breakthrough in research, particularly dementia will have an enormous impact on social cost which is often underestimated.     

Efficient Liability Rules: Complete Characterization

Received May, 18, 2000; revised version received March, 19, 2001     

Varietal Licensing Standards and Canadian Wheat Exports

Canada's wheat grading system is largely based on visual criteria and it is based on relatively high quality standards. A strict varieties licensing system exists to maintain the integrity of the grade standards. One of the consequences of the licensing system is that higher yielding, lower or different quality wheats have not been grown in Canada until recently. The basic objective of this paper is to examine some of the consequences of the regulatory strategy of limiting wheat production to the traditional high quality wheats. This question is analyzed in the context of important changes in the international grain markets. Using a partial equilibrium trade model this paper estimates that if higher yielding wheats were permitted to be grown, annual producer gains would be 5 to 17 percent of current net farm income.
Le classement des blés au Canada est basé sur des critères visuels qui sont de hautes qualités. Le système actuel d'homologation des variétés est tel que l'intégrité de ce système est maintenue. En conséquent, ce système n'a pas encouragé la cultivation des blés de hauts rendements ou des varietés différentes que tout récemment. L'objectif principal de cette étude est d'examiner quelques unes des conséquences de la stratégic de la réglementation visant à limiter la production du blé aux variétés de hautes qualités. Cette question est adressée dans le contexte des changements importants qui ont eu lieu dans le marché international des grains. A l'aide d'un modèle d'équilibre partiel des échanges, la présente étude démontre gu'en permettant la production des blés de hauts rendements, le gain annuel aux producteurs serait de 5 à 17 pourcent du revenue agricole net.     

Cardinality-based equality of opportunities

We study possible rankings of opportunity profiles. An opportunity profile is a list of opportunity sets, one for each agent in the society. We compare profiles on the basis of the notion of “equality of opportunities”. Our main results show the necessary and sufficient conditions for this comparison to be made using exclusively the information provided by two cardinal measures: the number of common alternatives in all sets of a given profile and the difference between the number of alternatives in the individual sets. We also show that, under additional axioms, we can combine these criteria only in a weighted procedure or in some lexicographic refinements of a weighted procedure.