Some critics are of the view that the population should be related to the total wealth of a country instead of the food supply of a country. This is the basis of the optimum theory of population. These economists believe that food supply is not an issue as we can import food from abroad in exchange for its other goods produced in the country. The concept of countries having a point of optimum population is summarised in Cannon’s theory of optimum population which explores the relationship between a country’s population and the resulting per capita income. According to Cannon’s theory, the optimum population is the population size that produces maximum returns in the form of income. It is “the best and the most desirable size of a country’s population consistent with its resources”.