2.1 Describing the development of the population

An individual is born, lives and dies. All of this goes on in the population simultaneously. The development of the population is the end-result of births, deaths and geographic movement, i.e. migration. These changes are collectively known as demographic phenomena. They create the framework to which society and its services (such as health care and the school system) have to adapt.

In order to understand the development of the population, we need to have various statistical indicators with which to describe population phenomena. These provide us with tools that allow for comparisons across different years and even centuries. Statistical indicators describing population phenomena also make it possible to compare different populations, for instance those living in different cities or countries. However, statistical indicators are condensed information and the interpretation of that information requires caution.

In most cases these statistics indicate the proportion of demographic phenomena in the total population or in certain population segments. For example, the number of children born during the year may be compared to the whole population.

The rates are usually presented in per cent or per mille. Per mille indicates the occurrence of the population phenomenon per one thousand (1,000) persons. For example, in the case of birth rate we might say that around 11 children were born per one thousand persons (or population) in Finland in 2007, while in Sweden 12 children were born per one thousand persons.