Les comparaisons internationales de prix, de volume et de productivité. Application à l'agriculture

Résumé En Fr

This paper focuses on empirical problems raised by international comparisons of quantities (such as the construction of real values for the Gross Domestic Product or for sectoral output), international comparisons of prices (i.e. purchasing power parities), an£l international comparisons of productivity. Micro-economic theory of the firm provides a rigorous framework for defining theoretical indexes that should be used for aggregating prices and quantities. A price index can be defined for producers as well as consumers, as the ratio of costs or revenue functions in two price situations. In empirical applications, these theoretical indexes must be approximated by index number formulas in order to avoid econometric estimation. Several empirical index numbers are presented in this paper, focusing on superlative formulas that give consistent comparisons between more than two countries. One can choose an index which is the most useful to a particular case , since all index numbers do not have similar axiomatic properties. In empirical studies , it is advocated that the Fisher index is particularly appropriate for the measurement of changes of prices and quantities over time. For the construction of purchasing power parities, the comparison of quantities and the measurement of productivity gaps between countries , economic theory suggests that indexes derived from micro-economic theory such as the EKS or the Caves-Christensen-Diewert index should be preferred to the Geary-Khamis index which is used by international organizations. Beyond theoretical aspects, many empirical problems remain. They are caused by the data limitations , the aggregation procedure and the particularities of the agricultural sector. On the basis of a study on the comparative competitiveness of the United States and European agriculture, several empircal solutions to these difficulties are suggested. The problems of transitivity and the problem of pricing the fixed factors are still a matter of debate.

Cet article examine les problèmes posés par les comparaisons internationales de quantités (valeurs réelles), de prix (parités de pouvoir d'achat) et de productivité. La théorie microéconomique du producteur donne des bases rigoureuses pour définir des indices théoriques et agréger prix et quantités. Dans des applications pratiques, ces indices théoriques doivent être approximés par des formules empiriques. Plusieurs indices empiriques sont présentés. Le choix entre ceux-ci peut être guidé par une approche «axiomatique», toutes les formules n'ayant pas les mêmes propriétés mathématiques. Au delà des aspects théoriques, de nombreux problèmes pratiques se posent dans les comparaisons internationales. Sur la base d'une étude des performances comparées des agricultures américaine et européenne entre 1973 et 1989, différentes solutions à ces problèmes empiriques sont présentées.