In pre-industrial societies and in agricultural social groups, there is emphasis on cooperative activities, joint families, joint occupations and community living. These are the basic motives for high fertility rate. In agricultural societies children are valued due to economic, social, religious and cultural factors. Economically they start earning and helping the parents at very young age.
A strong motivation is used for procreating more children, at present time. In most of the developed countries the psychological or motivational factors are in favor of low fertility. Among the motivational factors, the most important factors are desire for small family, availability of means of birth control and emphasis on sex enjoyment.
Some occupations are more risky and creates so many health problems. Some industries are clinked with various diseases. Death rate in some occupations is high while low in others. For example; death rate is high in workers who are working in the mines and chemical industries. Occupation provides income and standard of living which influence death rate.
Biological factors include age of the mother, order of birth, time interval between births etc. it has been observed that fetus and post-natal mortality rates are high at the young age of the mother like below 19 for the first birth order up to the age of 29, these rates decline and then increase after it. The maturity of an infant is also an important factor.
There were several factors (Famines and food shortage, Epidemics, War and Terror etc) have led to high mortality rates up to 19th century. However after the agricultural and industrial revolutions, mortality rates have fallen everywhere. Following were the most important factors for the decline of the mortality rate. Agricultural revolution started in England around 1700 AD and spread throughout Europe and the European settlements in the world.
Population change has been defined in terms of mortality, fertility and migration. According to the United Nations, mortality is the percentage of death in the population. Death has been defined by WHO, death is the permanent disappearance of all evidence of life at any time after birth has taken place. This definition proves that death can occur only after live birth.
These terms are used for international migration or migration from one country to another. Immigration is coming from one country to another and emigration is going from one country to another. For example; immigration of Hindus from Bangladesh to India and emigration of Indians to united states.
Human migration is the movement of people from one place to another and the intentions of settling to the new location can either be permanent or temporary. This type of movement usually covers a long distance, probably from one country to another. Nomadic movements are not considered as migration as their intention is not to settle in any new place but it’s all seasonal.