Published online by Cambridge University Press: 28 July 2009
The nebula-like cluster is a common trait in the spatial picture of man's attributes. Take any atlas showing economic or cultural elements and you will find an endless sequence of spatial distributions which have a concentrated core surrounded by a border zone of outwards decreasing density.
There is nothing such as one single and simple explanation of the “nebula-distribution”. But nevertheless one particular process which creates this type of distribution—temporarily or as an end result—seems to be highly significant: diffusion of techniques and ideas through the network of social contacts.
(1) The phenomenon as such has of course been noticed many times. In American writings reference should be made to Pemberton, , The Spatial Order of Culture Diffusion, Sociol. and Soc. Research, XXII (1936)Google Scholar and McVoy, E. C., Patterns of Diffusion in the United States., Amer. Sociol. Rev. V (1940), 219–227.CrossRefGoogle Scholar
(2) A full treatment is found in Hägerstrand, T., Innovationsförloppet ur korologisk synpunkt (Lund 1953).Google Scholar Cf. also Hägerstrand, T., Quantitative Techniques for Analysis of the Spread of Information and Technology, in Education and Economic Growth (Ed. Anderson-Bowman, , Chicago 1965).Google Scholar
(3) In Sweden migration is recorded in full detail. It is possible from the population registers to follow each individual from dwelling to dwelling all his life. The data go back about 200 years.
(4) Single individuals or family-groups.
(5) Several other routines for finding a receiver are conceivable. In the first instance a system of concentric circles seems to be nearest at hand. In practice, however, the square cells are easier to handle and this is particularly so when we are going to apply the model on unevenly distributed populations as demonstrated later.
(6) The runs were performed on the electronic computer SMIL of Lund and I am indebted to professor Carl-Erik Fröberg for taking care of the machine-program. The random numbers were produced by a built-in routine.