The crowding of town and country, which has become greater and greater in recent years, depends on a combination of two factors, viz., (i) an increase in the number of individual inhabitants and (ii) the more rapid circulation of the existing population. The latter is due to a change in habits, and this has been rendered possible by the growth of motorised transport in the forms of private cars and of public conveyances, such as tourist or ‘sight-seeing’ omnibuses. In many of its effects, an increase in the rapidity of circulation of human beings is equivalent, as in the case of bank notes, to an increase in total numbers. It follows that the optimal maximum number of inhabitants in a country tends to be smaller as the average rate of circulation increases.

C. D. Broad, Autobiographical notes (August 24 1954 to December 31 1968), in Joel Walmsley (ed.) C. D. Broad: key unpublished writings, London, 2022, pp. 13-110, p. 91