Add the number or percentage of young dependants and elderly dependants, divide by the working-age population, and multiply by . The result is the number of dependants per 100 working-age people.
This is HL-only content in IB ESS subtopic 8.1, Human populations. The exact age boundaries may differ between datasets, so always use the categories stated in the question.
If the pyramid gives absolute population numbers, use numbers throughout. If it gives percentages, use percentages throughout because the numerator and denominator share the same units. For five-year bands, include , , and as young dependants and every band from as elderly dependants.
Calculation Method
An age-sex pyramid normally separates males and females into five-year age bands. Unless the question asks for a sex-specific ratio, combine the male and female values for every relevant band.
| Step | What to do | Worked example |
|---|---|---|
| 1 | Add all values in the young-dependent bands | Ages : |
| 2 | Add all values in the elderly-dependent bands | Ages : |
| 3 | Find the working-age population | Ages : |
The dependency ratio is therefore approximately 56 dependants per 100 working-age people. A ratio of does not mean that of the total population is dependent; it compares dependants only with the working-age group.
A high ratio suggests greater potential pressure on workers and governments to fund services such as education, healthcare and pensions. However, it is a demographic indicator rather than a direct measure of employment: some working-age people are unemployed, while some people above the retirement age continue working.
IB Exam Technique
Show the age groups selected, include both sexes, write the formula, substitute values, and interpret the result using “dependants per 100 working-age people.” If values are read from a graph, acknowledge that the answer is an estimate. Avoid the common misconception of dividing dependants by the total population.
