The change depends chiefly on:
1. Birth rate [The birth rate (along with mortality and migration rate) are used to calculate population growth. The crude birth rate is the number of live births per year per 1,000 mid-year population.]
2. Mortality rate [Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time.]
3. Migration: Human migration is the movement of people from one place to another with the intention of settling, permanently or temporarily at a new location. The movement is often over long distances and from one country to another, but internal migration is also possible; indeed, this is the dominant form globally.]
4. Social dynamism [Social dynamism (or socio dynamics) can refer to the behavior of groups that results from the interactions of individual group members as well to the study of the relationship between individual interactions and group level behaviors.]
These determining factors of population change rely upon age, gender, marriage, social structure, religious values, education, profession etc. For example, age structure of population of a country is divided into three stages- young, adult and old. The country which has more young and old population will have a lower birth rate and the country with higher number of adults will have higher birth rate. Gross birth rate depends on the age of marriage of a boy or girl. Birth rate will be higher in a country where child marriage is rampant. Birth rate and mortality rate brings about change in the population structure of a country. So, it can be said, changeability of population means the change of structure of population.
Some other factors on which population change depends: Some aspects are closely associated with the structural change of population. They are-
1. Geographical environment
2. Climate
3. Natural resources
4. Fertility
5. Elevation of land
6. Developed communication system
7. Education
8. Advanced medical facility
9. Health services etc.
The more a country is educated, the more developed it is. The influence of knowledge toward change tends to bring about change in values and beliefs of people. They are encouraged to form small families. Profession also makes a difference in the birth rate. The birthrate among farmers, laborers, and fishermen is high whereas it is low among doctors, teachers, engineers etc.