The relationship between population and resources forms the basis of the optimum population, theory. Edwin Cannan (1861- 1935), an English Economist, has been given the credit for defining what later came to be known as the concept of "Optimum Population."
The first beginnings of this concept may be traced to the writings of a German professor, Karl Winkelblech (1810-1865), who while describing population theory and policy, classified nations into three categories according to the size of their population: (1) Under-populated nations; (2) Over-populated nations; and (3) Nations with normal populations, meaning a size favourable to the greatest possible productivity.
Cannan used the term "optimum population" as synonymous with the best possible population, and clarified this in the following words, "At any given time, the population which can exist on a given extent of land, consistent with the greatest productiveness of industry at that time, is definite."
The concept of optimum population has been interpreted in several ways, "to mean the size of the population which results in the highest per capita income, the highest productivity as measured in different manners, or the highest level of other less well-defined economic indicators, such as economic welfare, level of living, real income and, in some cases, employment."
Some writers, considering the concept of the economic optimum as being too restrictive, have included in it the total well-being, health, and longevity of a nation, the ideal family size, and the conservation of natural resources, power, defense and other spiritual, cultural and aesthetic factors.
According to most writers, however, the economic optimum was the main consideration in the optimum population theory, and gradually the idea of a population of optimum size for maximum production was accepted. Later developments, however, provoked a critical re-examination of this theory.
One noteworthy aspect of the concept of optimum population was that it was a reconciliation of the optimistic and the pessimistic theories of population, for it implied that the growth of population was beneficial up to a certain point, after which any further growth was harmful.
This theory has been criticised on several grounds. Several writers have challenged its practical applicability by expressing doubts whether optimum population in the sense of an optimum point can ever be determined.
Actually, very few attempts have been made to determine the optimum population of any country. (An American demographer put the optimum population size for the United States of America at 120 million.
Alfred Survey worked out a figure of between 50 and 75 million for France. Coale and Hoover arrived at the conclusion that one-fourth of the rural population of India was useless).
Some, critics of this theory have challenged the very concept of optimum population, which is essentially a static concept. According to these critics, the theory is based on the assumption of a ceteris paribus condition for all other factors such as technology, resources, social structure, external trade, etc. Such an assumption is, of course, highly unrealistic.
The idea of an optimum population attracted much attention in the 1920's and the 1930's. In recent times, Survey has once again discussed this theory at great length and has defined optimum Population as that population which best assures the realisation of Pre-determined objective, not so much as an absolute theoretical concept but as a convenient tool.