Demographic Gravitation

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Demographic gravitation is a concept of "social physics"[1], introduced by Princeton University astrophysicist John Quincy Stewart[2] in 1947[3]. It is an attempt to use equations and notions of classical physics - such as gravity - to seek simplified insights and even laws of demographic behaviour for large numbers of human beings. A basic conception within it is that large numbers of people, in a city for example, actually behave as an attractive force for other people to migrate there, hence the notion of demographic gravitation. It has been related[4] to W. J. Reilly's law of retail gravitation[5][6], George Kingsley Zipf's Demographic Energy[7], and to the theory of Trip distribution.

Writing in the journal Sociometry, Stewart set out an "agenda for social physics." Comparing the microscopic versus macroscopic viewpoints in the methodology of formulating physical laws, he made an analogy with the social sciences:

Fortunately for physics, the macroscopic approach was the commonsense one, and the early investigators - Boyle, Charles, Gay-Lussac - were able to establish the laws of gases. The situation with respect to "social physics" is reversed... If Robert Boyle had taken the attitude of many social scientists, he would not have been willing to measure the pressure and volume of a sample of air until an encyclopedic history of its molecules had been compiled. Boyle did not even know that air contained argon and helium but he found a very important law. [8]

Stewart proceeded to apply Newtonian formulae of gravitation to that of "the average interrelations of people" on a wide geographic scale, elucidating such notions as "the demographic force of attraction," demographic energy, force, potential and gradient.[9]

[edit] Key Equations

The following are some of the key equations with plain english paraphrases from his article in Sociometry:

F = \frac{N1 . N2}{d^2} Force = (population 1 X population 2) / (distance squared)

E = \frac{N1 . N2}{d} Energy = (population 1 X population 2) / distance; this is also Zipf's determinant

PN1 = \frac{N2}{d} Potential of population 1 = population 2 / distance

P = \frac{N}{d} Potential = population / distance, in persons per mile

Gradient = \frac{N}{m^2} Gradient = persons / (mile squared)

The potential of population at any point is equivalent to the measure of proximity of people at that point (this also has relevance to Georgist economic rent theory).

For comparison, Reilly's retail gravity equilibrium is paraphrased as:

\frac{N1}{d^2} = \frac{N2}{d^2}

Population 1 / (distance to balance, squared) = Population 2 / (distance to balance, squared)

[edit] See also

  • Stewart, J.Q., 1947. Empirical Mathematical Rules Concerning the Distribution and Equilibrium of Population, Geographical Review, Vol 37, 461-486.
  • Stewart, J.Q., 1950. Potential of Population and its Relationship to Marketing. In: Theory in Marketing , R. Cox and W. Alderson (Eds) ( Richard D. Irwin, Inc., Homewood, Illinois).
  • Zipf, G.K., 1946. The Hypothesis on the Intercity Movement of Persons. American Sociological Review, vol. 11, Oct
  • Zipf, G.K., 1949. Human Behaviour and the Principle of Least Effort. Massachusetts

[edit] References

  1. ^ Stewart, J.Q., 1950. The Development of Social Physic, American Journal of Physics, Vol 18, 239-253
  2. ^ Vecchia, Karla J., John Q. Stewart Papers (C0571)1907-1970s A Finding Aid, Manuscripts Division Department of Rare Books and Special Collections Princeton University Library 2004 [1]
  3. ^ Stewart, John Q., "Demographic Gravitation: Evidence and Applications," Sociometry, Vol. 11, No. 1/2. (Feb. - May, 1948), pp. 31-58. [2]
  4. ^ Kostelanetz, Richard (Ed.), "Beyond Left and Right: Radical Thought for Our Times, William Morrow & Co., New York, 1968."
  5. ^ Reilly, W.J. (1929) “Methods for the Study of Retail Relationships” University of Texas Bulletin No 2944, Nov. 1929.
  6. ^ Reilly, W.J., 1931. The Law of Retail Gravitation, New York.
  7. ^ Stewart, J.Q. (1948) “Demographic Gravitation: Evidence and Application” Sociometry Vol. XI Feb.-May 1948 pp 31-58.
  8. ^ Stewart, John Q., "Demographic Gravitation: Evidence and Applications," Sociometry, Vol. 11, No. 1/2. (Feb. - May, 1948), pp. 31-58. [3]
  9. ^ Stewart, John Q., "Demographic Gravitation: Evidence and Applications," Sociometry, Vol. 11, No. 1/2. (Feb. - May, 1948), pp. 31-58. [4]