This paper is divided into two parts which deal with closely connected issues, The first section of the paper explores the structure of consumer demand systems necessary and sufficient for exact aggregation. The second section addresses a related empirical question: what, if anything, do the...

In this paper we provide suffic ient condi tions, which, when combined with recent developments in the theory of exact aggregation, permit estimation of group specific demand systems when micro-level information is unavailable. We illustrate the approach by estimating group specific cost of...

An individual demand function is said to satisfy the finite basis property when its set of Engel curves has a finite spanning subset. In the present letter we discuss why this property underlies the theory of exact aggregation

This letter explores the robustness (in an approximating sense) of a class of demand systems which have been discussed by Gorman. This class is of fundamental interest because it is known to be the only class of demand systems which permits exact aggregation. We discuss the reasons which...