The essay on the principle of population an important work of Malthus is a landmark in the history of population studies. The theme of the Essay was mainly to argue that the tendency of the population to grow faster in relation to its means of subsistence has led to human misery and placed several obstacles in the path of human progress. In 1803, Malthus published the second edition of his essay, a much expanded and changed edition which can't really be called a re print of the 1797 essay, for in the new edition the emphasis was more on arguments against the poor laws than on country arguments against the opinions of Condorcet and Godwin.
Neo- Maltusian theory
Neo-Malthusians maintain that although the gloomy predictions of Malthus may have been pre-mature they are basically correct.
According to Anti Malthusians' world's resources are adequate for a much larger population. Exploitation not over population is the basic cause of world hunger.
Demographic Transition theory
Two different interpretations have been given for this theory.One by Frank Notestein says that every country passes through three stages of population growth; 1. High birth rate and high death rate ii.High birth rate and low death rate (population explosion) iii.Low birth rate and low death rate.
In western nations the desire for high standard of living led to the reductions in the birthrate .These nations are approaching a new equilibrium with both birthrates and death rates quite low and little population growth. This is explained by the theory of demographic transition -the theory that industrial and commercial development first cuts the death rate but creates a desire for smaller families and eventually cuts the birthrate.
The other theory is given by C.P Blacker .There are five phrases in this theory. i.High stationary phase marked by high fertility and mortality rate.
ii.Early expanding phase marked by high fertility and high but declining mortality.
iii.Late Expanding phase with declining fertility but mortality declining more rapidly.
iv.Low stationary phase with low fertility and equally low mortality.
v. Declining phase with low mortality, low fertility and an excess of deaths over births.
Optimum population theory
According to Canan the propounder of this theory population must grow upto certain desired level after which further growth is harmful. The two important principles of this theory are:
1. When there is an increase in population than the ratio between the total population and the working population remains almost constant.
2. When at a point of time the population of a country increases the natural resources capital and technical know how do not change with the result that after sometime the law of diminishing returns begins to operate. This law provides that for maximum production all the sources of production should be combined in that proper ratio than it shall not be possible to have maximum production.