7. Population as the basis for key ratios

In the previous lesson you learnt about the contents of population phenomena. This lesson will introduce the means by which to describe various population phenomena.

In demography key ratios are the main means to describe and explain population phenomena. With the help of key ratios we can examine changes occurring in population phenomena, such as rates of births, deaths, migration, marriages and divorces.

Changes taking place in the population can be studied in various ways. Key ratios calculated from population phenomena can be limited to concern a certain time period or a specific population group. The concepts of cross-sectional information and period information are connected with a phenomenon viewed according to a time period. When examining a certain population group, we talk about the cohort, risk population and mean population.

The aim of this lesson is to teach you about the contents of these concepts and their application in demographic research.