How do populations change?
Populations are always changing. There are natural factors, like people having children or dying, and economic and social factors, like war, famine or jobs, that make people move to or away from an area.
Natural factors
The number of babies born in an area.
The number of deaths in a population.
Births minus deaths. If there are more deaths than births, it is a negative number and the population gets smaller.
People on the move: migration
When a person from another area moves into the area. That person is an immigrant.
When a person moves away from the area. That person is an emigrant.
In the last century, many people in Spain moved away from rural areas (villages and the countryside) into urban areas (towns and cities), because cities offered more work and better services. This is called the rural exodus. Today most people in Spain live in cities, and some villages have very few people left.
In some regions fewer babies are born every year, but the population is still increasing. How is this possible? Because more people immigrate into the region than emigrate from it!