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The theory is based on an interpretation of demographic history developed in 1930 by the American demographer Warren Thompson (1887–1973). [6] Adolphe Landry of France made similar observations on demographic patterns and population growth potential around 1934. [7]
Thomas Robert Malthus, after whom Malthusianism is named. Malthusianism is a theory that population growth is potentially exponential, according to the Malthusian growth model, while the growth of the food supply or other resources is linear, which eventually reduces living standards to the point of triggering a population decline.
The change in total population over a period is equal to the number of births, minus the number of deaths, plus or minus the net amount of migration in a population. The number of births can be projected as the number of females at each relevant age multiplied by the assumed fertility rate.
Another limitation of this theory is the belief that overall income is a key factor of population health, [35] implying that wealthy countries will have various solutions for their rapidly rising populations. [36] An expanding population can be considered as an increase of available human capacity for increasing food production. [37]
Theory of population may refer to: Malthusianism, a theory of population by Thomas Malthus (1766–1834) An Essay on the Principle of Population, the book in which Malthus propounded his theory; Neo-Malthusian theory of Paul R. Ehrlich (born 1932) and others; Theory of demographic transition by Warren Thompson (1887–1973)
Human population projections are attempts to extrapolate how human populations will change in the future. [2] These projections are an important input to forecasts of the population's impact on this planet and humanity's future well-being. [3] Models of population growth take trends in human development and apply projections into the future. [4]
P 0 = P(0) is the initial population size, r = the population growth rate, which Ronald Fisher called the Malthusian parameter of population growth in The Genetical Theory of Natural Selection, [2] and Alfred J. Lotka called the intrinsic rate of increase, [3] [4] t = time. The model can also be written in the form of a differential equation:
In demography and medical geography, epidemiological transition is a theory which "describes changing population patterns in terms of fertility, life expectancy, mortality, and leading causes of death."