ABSTRACT
The population activity models are those which have been available since the 1960s and have been reviewed here. We are now arguing, however, that ~Ie can extend these models so as to begin to model the distribution of physical infrastructure, the subsystem shown in the centre of the diagram (with the exception as yet of dealing with the evolution of transport networks) and, in the same way, the supply of economic activity in the service sector (which may be well over 50 per cent of an advanced economy). The remaining gap, therefore, is the spatial distribution of basic economic activity.
