Demographic Gravitation
Encyclopedia
Demographic gravitation is a concept of "social physics", introduced by Princeton University
astrophysicist John Quincy Stewart
in 1947. 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 to W. J. Reilly's law of retail gravitation
, George Kingsley Zipf's Demographic Energy, and to the theory of Trip distribution
through gravity models Trip distribution#Gravity model.
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
:
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.
:
(Demographic Force = (population 1 multiplied by population 2) divided by (distance squared))
(Demographic Energy = (population 1, multiplied by population 2) divided by distance; this is also Zipf's determinant
(Demographic Potential of population at point 1 = population at point 2, divided by distance)
(Demographic Potential in general = population divided by distance, in persons per mile)
(Demographic Gradient = persons per (i.e. divided by) square mile)
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 Economic rent#Land rent).
For comparison, Reilly's retail gravity equilibrium (or Balance/Break Point) is paraphrased as:
(Population 1 divided by (distance to balance, squared) = Population 2 / (distance to balance, squared))
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....
astrophysicist John Quincy Stewart
John Quincy Stewart
John Quincy Stewart was an American astrophysicist.He obtained his Ph.D. in physics from Princeton University in 1919...
in 1947. It is an attempt to use equations and notions of classical physics
Classical physics
What "classical physics" refers to depends on the context. When discussing special relativity, it refers to the Newtonian physics which preceded relativity, i.e. the branches of physics based on principles developed before the rise of relativity and quantum mechanics...
- 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 to W. J. Reilly's law of retail gravitation
Reilly's law of retail gravitation
In economics, Reilly's law of retail gravitation states that larger cities will have larger spheres of influence than smaller ones, meaning people travel farther to reach a larger city....
, George Kingsley Zipf's Demographic Energy, and to the theory of Trip distribution
Trip distribution
Trip distribution , is the second component in the traditional four-step transportation forecasting model...
through gravity models Trip distribution#Gravity model.
Writing in the journal Sociometry
Sociometry
Sociometry is a quantitative method for measuring social relationships. It was developed by psychotherapist Jacob L. Moreno in his studies of the relationship between social structures and psychological well-being....
, Stewart set out an "agenda for social physics." Comparing the microscopic
Microscopic
The microscopic scale is the scale of size or length used to describe objects smaller than those that can easily be seen by the naked eye and which require a lens or microscope to see them clearly.-History:...
versus macroscopic
Macroscopic
The macroscopic scale is the length scale on which objects or processes are of a size which is measurable and observable by the naked eye.When applied to phenomena and abstract objects, the macroscopic scale describes existence in the world as we perceive it, often in contrast to experiences or...
viewpoints in the methodology of formulating physical laws, he made an analogy with the social sciences
Social sciences
Social science is the field of study concerned with society. "Social science" is commonly used as an umbrella term to refer to a plurality of fields outside of the natural sciences usually exclusive of the administrative or managerial sciences...
:
Fortunately for physics, the macroscopic approach was the commonsense one, and the early investigators - BoyleRobert BoyleRobert Boyle FRS was a 17th century natural philosopher, chemist, physicist, and inventor, also noted for his writings in theology. He has been variously described as English, Irish, or Anglo-Irish, his father having come to Ireland from England during the time of the English plantations of...
, CharlesCharlesCharles is a given name for males and is borrowed from the French form of the Latin Carolus Charles is a given name for males and is borrowed from the French form of the Latin Carolus...
, 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.
Stewart proceeded to apply Newtonian
Newtonian
Newtonian refers to the work of Isaac Newton, in particular:* Newtonian mechanics, also known as classical mechanics* Newtonian telescope, a type of reflecting telescope* Newtonian cosmology* Newtonian dynamics...
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.
Key equations
The following are some of the key equations (with plain English paraphrases) from his article in sociometrySociometry
Sociometry is a quantitative method for measuring social relationships. It was developed by psychotherapist Jacob L. Moreno in his studies of the relationship between social structures and psychological well-being....
:
(Demographic Force = (population 1 multiplied by population 2) divided by (distance squared))
(Demographic Energy = (population 1, multiplied by population 2) divided by distance; this is also Zipf's determinant
(Demographic Potential of population at point 1 = population at point 2, divided by distance)
(Demographic Potential in general = population divided by distance, in persons per mile)
(Demographic Gradient = persons per (i.e. divided by) square mile)
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
Economic rent
Economic rent is typically defined by economists as payment for goods and services beyond the amount needed to bring the required factors of production into a production process and sustain supply. A recipient of economic rent is a rentier....
theory Economic rent#Land rent).
For comparison, Reilly's retail gravity equilibrium (or Balance/Break Point) is paraphrased as:
(Population 1 divided by (distance to balance, squared) = Population 2 / (distance to balance, squared))
See also
- Reilly's law of retail gravitationReilly's law of retail gravitationIn economics, Reilly's law of retail gravitation states that larger cities will have larger spheres of influence than smaller ones, meaning people travel farther to reach a larger city....
- Trip distributionTrip distributionTrip distribution , is the second component in the traditional four-step transportation forecasting model...
: Gravity Model - George Kingsley Zipf's Demographic Energy
- Central place theoryCentral Place TheoryCentral place theory is a geographical theory that seeks to explain the number, size and location of human settlements in an urban system. The theory was created by the German geographer Walter Christaller, who asserted that settlements simply functioned as 'central places' providing services to...
- Johann Heinrich von ThünenJohann Heinrich von ThünenJohann Heinrich von Thünen was a prominent nineteenth century economist. Von Thünen was a Mecklenburg landowner, who in the first volume of his treatise, The Isolated State , developed the first serious treatment of spatial economics, connecting it with the theory of rent...
's spatial economics - Walther Christaller's central place theoryCentral Place TheoryCentral place theory is a geographical theory that seeks to explain the number, size and location of human settlements in an urban system. The theory was created by the German geographer Walter Christaller, who asserted that settlements simply functioned as 'central places' providing services to...
- Alfred WeberAlfred WeberAlfred Weber was a German economist, sociologist and theoretician of culture whose work was influential in the development of modern economic geography.-Life:...
's least cost location theory.
- Economic rentEconomic rentEconomic rent is typically defined by economists as payment for goods and services beyond the amount needed to bring the required factors of production into a production process and sustain supply. A recipient of economic rent is a rentier....
: Land rent.
- John Quincy StewartJohn Quincy StewartJohn Quincy Stewart was an American astrophysicist.He obtained his Ph.D. in physics from Princeton University in 1919...
, 1947. Empirical Mathematical Rules Concerning the Distribution and Equilibrium of Population, Geographical Review, Vol 37, 461–486. - John Quincy StewartJohn Quincy StewartJohn Quincy Stewart was an American astrophysicist.He obtained his Ph.D. in physics from Princeton University in 1919...
, 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 P1 P2/D 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