The "Demographic Transition" is a model that describes population change over time. It is based on an interpretation begun in 1929 by the American demographer Warren Thompson, of the observed changes, or transitions, in birth and death rates in industrialized societies over the past two hundred years or so.
The theory of Demographic Transition is a theory that throws light on changes in birth rate and death rate and consequently on the growth rate of the population. Along with the economic development, tendencies of birth-rate and death rate are different. Because of it, the growth rate of the population is also different.