| Abstract: | The gravity model in its basic forms postulates that the volume of interaction between two places will be positively related to the populations (masses) of the two places and inversely related to their distance apart. Although it is not strictly speaking a hierarchical model, it is often used to explain flows among places that constitute a hierarchical spatial system. This paper is specifically concerned with the effect of hierarchical spatial structure on the performance of the gravity model. Accordingly, I will examine first the effect of hierarchical structure on the volume of interaction between places and second the degree to which the gravity model incorporates these hierarchical effects. Third, suggestions will be made for the improvement of the gravity model's performance by an explicit incorporation of a hierarchical element. The performance of the gravity model will be examined for both one-way and two-way flows between places. |
