The Effects of Competition on Variation in the Quality and Cost of Medical Care

We estimate the effects of hospital competition on the level of and the variation in quality of care and hospital expenditures for elderly Medicare beneficiaries with heart attack. We compare competition's effects on more-severely ill patients, whom we assume value quality more highly, to the effects on less-severely ill, low-valuation patients. We find that low-valuation patients in competitive markets receive less intensive treatment than in uncompetitive markets, but have statistically similar health outcomes. In contrast, high-valuation patients in competitive markets receive more intensive treatment than in uncompetitive markets, and have significantly better health outcomes. Because this competition-induced increase in variation in expenditures is, on net, expenditure-decreasing and outcome-beneficial, we conclude that it is welfare-enhancing. These findings are inconsistent with conventional models of vertical differentiation, although they can be accommodated by more recent models.     

The signs of the co-state variables and sufficiency conditions in a class of optimal control problems

A class of optimal control problems is identified, for which co-state variables have definite signs and the Maximum Principle is sufficient for optimality. The restrictions defining this class of problems are given an economic interpretation.     

Gottfried Haberler's 1930 Reformulation of Comparative Advantage in Retrospect

In 1930 Gottfried Haberler freed the doctrine of comparative advantage from its association with David Ricardo's labor theory of value and provided us with its modern opportunity‐cost formulation. Haberler's reformulation of comparative advantage revolutionized the theory of international trade and laid the conceptual foundation of modern trade theory. On the occasion of its 75th anniversary, a symposium has been organized to reflect on and celebrate one of the most durable and fruitful ideas in the history of economic thought. In this introductory paper I revisit Haberler's original formulation, which was published in German in the Weltwirtschaftliches Archiv.     

Hybrid Choice Models: Progress and Challenges

We discuss the development of predictive choice models that go beyond the random utility model in its narrowest formulation. Such approaches incorporate several elements of cognitive process that have been identified as important to the choice process, including strong dependence on history and context, perception formation, and latent constraints. A flexible and practical hybrid choice model is presented that integrates many types of discrete choice modeling methods, draws on different types of data, and allows for flexible disturbances and explicit modeling of latent psychological explanatory variables, heterogeneity, and latent segmentation. Both progress and challenges related to the development of the hybrid choice model are presented.     

Index numbers and consistency in aggregation

This paper is an analysis of the concept of consistency in aggregation. This is the conjunction of three requirements: (i) for any given partition of the variables, two-stage aggregation is consistent, (ii) that each subaggregate and the overall aggregate have the same functional form, and (iii) that all partitions of the variables are feasible. We show that in the scalar case this results in a quasi-additive functional form. The generalization to many attributes is however shown to lead to few restrictions.     

Monetary anticipations and the demand for money: Reply to MacKinnon and Milbourne

MacKinnon and Milbourne (1984), in an extended comment on Carr and Darby (1981), claim that money supply shocks do not enter the money demand function for the United States. This reply discusses the economic and econometric errors which led to this conclusion and presents further empirical evidence in support of our approach.