Population change refers to the change in the number of people due to birth, death and migration during a specific time.
Life expectancy is the number of years that an average person can expect to live. The major cause of the sudden change in the world’s population is the imbalance in the birth rate and the death rate.
Birth rate is the number of live babies born in a year for every 1000 people in the total population. Death rate is the number of people dying per 1000 people. The difference in the birth rate and the death rate of a country is called the natural growth rate.
A rapid growth in population is referred to as population explosion. If the birth rate is more than the death rate, then there is an increase in population. If the death rate is more than the birth rate, then there is a decrease in the population. A decrease in population is known as depopulation.
If birth rate and death rate are at the same level, there will be no natural growth. Migration is another cause of change in the size of a population which is the movement of people into and out of an area.
People who leave a country are called emigrants, while those who arrive in a country are called immigrants. A search for better employment opportunities is the main reason behind international migrations.
The pattern of population growth varies from country to country.