Aggregation of gravity models for journeys-to-work

Abstract

This paper deals with the use of gravity models to examine journeys-to-work. The purpose of the paper is to study very simple examples demonstrating that gravity models may be subject to serious misspecification in aggregate systems. The results are easily interpreted and serve to form a set of ideas that can be extended to general systems. As an outcome of the theoretical analysis, the paper has several implications to empirical work. It suggests a variety of modifications, experiments and procedures that can be carried out to enhance the performance of gravit models for journeys-to-work.