Based on the history of human population, the population size has slowly increased over time. Because of this increasing rate, resources were hard to find. Limiting factors, such as predation and diseases, have caused death rates to become high in order to control the growth or size of the population.

The social and economic factors which help in determining the reason why the population growth rates vary in different countries include the birthrates, death rates, and the age structure of a population.

Demographic transition shows the changes from high birthrates and death rates to low birthrate and death rate in a particular country. A demographer may ask these questions in order to determine if a country has already passed through a demographic transition:

1. Birthrate
a. What is the birthrate ten years ago?
b. What is the birthrate five years ago?
c. What is the birthrate for the current year?

2. Death rate
a. What is the death rate ten years ago?
b. What is the death rate five years ago?
c. What is the death rate for the current year?

3. Compare the birthrate and death rate. Is the birth rate higher than the death rate?

4. What is the age-structure of the population?

5. Is there any child policy imposed in the country?

Demographic transition shows the changes from high birthrates and death rates to low birthrate and death rate in a particular country. A demographer may ask these questions in order to determine if a country has already passed through a demographic transition: (Click to see explanation)

Age-structure diagrams show the age and gender groups in a population. This allows demographers to predict the rate of future population growth by studying the following patterns:

1. Percentage of the female population
Since females are able to reproduce, demographers can predict the birth rate in the future.

2. Percentage of children, teen, and adult population
If there are more children and teens than adults, demographers may predict that the population will surely grow twice its size after a few decades or once the younger population matures.