1.5 Population changes

The size of population is dependent on changes in the number of three factors - births, deaths and migration. The number of births increases population, while that of deaths decreases it. In English the term vital events is often used to talk about births and deaths. The effect of migration on the size of population can be either increasing or decreasing.

When examining only the effect of the number of births and deaths on the size of population, we refer to so-called natural increase or natural population growth. When the change in population size is viewed by taking migration into account as well, we talk about population growth.