Population pyramids can be used to find the number of economic dependents being supported in a particular population. Economic dependents are defined as those under 15 (children who are in full time education and therefore unable to work) and those over 65 (those who have retired). Of course, in some less economically developed countries children start work well before the age of 15, and in some more economically developed countries it is not usual to start work until 18 or 21, and people may work beyond the official retirement age of 65, but the definition provides an approximation. The government must plan the economy in such a way that the working population can support these dependents.
Population pyramids are also useful in planning for the future. They can be used in helping to predict changes in the age structure of the population over the next fifty or so years so that plans can be introduced to cope with the predicted changes. A current example of this are the British Government's plans to tackle the aging population in the United Kingdom.
Social historians may find information of interest in population pyramids. For example, the "chip" in the UK pyramid for males born in the 1920s is due to the large number of that group lost in action during the Second World War. Correspondingly for females, death in childbirth or death in girl infants due to being exposed by their parents will show on the female side of the pyramid. In Germany there are far more males aged 20-35 than females. This is due to an influx of immigrants from Turkey and Yugoslavia who came to work in Germany in the 1990s, leaving their wives and families behind