Reason for population growth : Following are the three main reasons for the growth of population of a country :
(1) High natality rate : In most of the countries, the birth rate is higher than death rate. Economic and social factors are responsible for high natality or birth rate.
(a) Economic factors : (i) agricultural dominance (ii) rural economy (iii) poverty
(b) Social factors : (i) illiteracy (ii) religious beliefs (iii) child marriage (iv) superstition (vi) inevitability of marriage (vii) joint family and indifference towards family planning etc.
(2) Relatively low mortality : The number of people dying every year per thousand of the population is called death rate. The main reason for the population explosion is the continuously decreasing death rate. There has been a continuous decrease in the death rate in India in the last decades, which is an important factor for population growth. It has following reasons :
(i) Protection from natural calamities : Man started living by building houses for his own safety so that he could be protected from natural calamities like cold, heat, rain, storm etc.
(ii) Development of agriculture : Due to agricultural development, the production of food grains increased and it became possible to supply it in sufficient quantity to the increasing population.
(iii) Storage facility : Due to advance storage facility, food grains become easily available to humans throughout the year.
(iv) Advanced transportation : With advanced transportation system, it became possible to reach food grains to places where there is shortage of food grains with immediate effect and in a short time.
(v) Control on diseases : Due to control on various diseases and increase in health measures the death rate has decreased and human's average age has increased from 30 to 60 years.
Immigration : Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration. It increases the population. This type of increase in population has been recorded due to the arrival of refugees and infiltrators from different countries in the borders of India.