“Migration, fertility and mortality are the basic fundamental elements determining population growth and demographic structure of a country.” Elucidate.

Demographic structure relates to studies of a population based on factors such as age, race, sex, and economic status, level of education, income level and employment, among others. It is influenced by basic fundamental elements such as: Migration, fertility and mortality.
Migration is permanent or semi-permanent change of residence of an individual or group of people over a significant distance. There can be various causes of migration such as over population, economic causes, technology, political causes, socio-religious causes, demographic causes and wars. The migration changes the demographic structure of the region.
Mortality rate refers to the number of deaths over a given period. It is expressed as number of deaths per 1000 population. It can be of different types:
Fetal mortality rate: The ratio of fetal deaths to the sum of the births in a year.
Infant mortality rate: The number of children dying under a year of age divided by the number of live births that year.
Maternal mortality rate: The number of maternal deaths related to childbearing divided by the number of live births in a year.
Fertility rate refers the average number of children that a woman bears over her reproductive span. Total Fertility Rate of 2.1 is considered to be a Replacement Rate, i.e. the rate at which a given population is able to produce enough offspring to replace itself. India’s TFR is around 2.6 while that of Pakistan is 3.2, which are much above the replacement rate.