PAPP101 - S02: How to measure demographic events

Age-sex structures and population pyramids (cont.)

Population pyramids

Population pyramids show the age-sex structure of a population. They are also potentially very informative about the history of a population and its future prospects.

There are a few simple rules for the construction of population pyramids:

• Population pyramids consist of two histograms placed on their side and back to back.
• They can show absolute numbers or percentages, but the x-axis must be labelled accordingly. When comparing populations, percentages should be used.
• If percentages are used, these must be calculated for each age-sex group from the total population (males and females), not just the total population of a single sex.
• Age is depicted on the y-axis, with the youngest at the bottom, and must be labelled accordingly.
• Age scale can be in single years, or five year age groups depending on the precision needed.
• The age groups used must be of equal width, apart from the final open ended age group.
• Statistics for males are plotted on the left, and females on the right.

Click to see an example of a population pyramid .