Dependency ratio and momentum at Higher Level: This statement is Higher Level only. It uses age-sex pyramids to work out how many dependents each worker supports, and to explain why a young population keeps growing long after families have become smaller.
Practise this as you read
- Calculate a dependency ratio from a pyramid, formula first.
- Outline issues for a country's future economy from its pyramid.
- Explain the role of population momentum in population growth.
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Who supports whom?: Children and old people are dependents: most of them are looked after by people who are economically productive. The dependency ratio compares the two groups.
The points to remember
- Dependents: under 15 and 65 and over; economically productive: 15 to 64.
- Dependency ratio = (aged 0-14 + aged 65+) ÷ aged 15-64 × 100.
- It tells you how many dependents there are for every 100 people of working age.
- Use numbers or percentages from the pyramid: the ratio comes out the same.
- It can be split: young dependency (0-14) and old dependency (65+).
Formula
Dependency ratio = (aged 0-14 + aged 65+) ÷ aged 15-64 × 100.
Read the pyramid
Japan, 2024: aged 0-14 = 11.4%, aged 65+ = 29.8%, so aged 15-64 = 100 - 11.4 - 29.8 = 58.8%.
Add the dependents
11.4 + 29.8 = 41.2%.
Divide and multiply
41.2 ÷ 58.8 × 100 = 70.1.
Say what it means
About 70 dependents for every 100 people of working age.
Two common slips: Divide by the working-age group, not by the whole population. And no unit: the answer is a number of dependents per 100 workers, not a percentage of the population.
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The guide makes a surprising point: the ratio is high at both ends of the demographic story, but for opposite reasons.
When is the ratio high?
- The ratio is high when fertility is very high: many children (Niger).
- It is also high when fertility is very low: many old people (Japan).
- It is lowest in between, when a big group of adults has few children and few elderly parents.
- Read it from the shape: a wide base, or a wide top, means many dependents.
| Country, 2024 | Aged 0-14 | Aged 65+ | Dependency ratio |
|---|---|---|---|
| Niger (fertility 5.9) | 46.6% | 2.6% | (46.6 + 2.6) ÷ 50.8 × 100 = 96.8 |
| Japan (fertility 1.2) | 11.4% | 29.8% | 70.1 |
| India (fertility 1.96) | 24.6% | 7.1% | 46.6 |
| World | 24.7% | 10.2% | 53.7 |
India sits in the low middle: fertility has fallen, but its large group of adults still has few old parents. Economists call this window a demographic dividend.
A paper may give you a pyramid and ask what it means for a country's future economy. Japan shows every point.
What a changing ratio means
- Falling births mean a smaller future workforce.
- A proportionally smaller workforce limits economic growth (GDP).
- Fewer workers must support more old people: a rising dependency ratio.
- More money is needed for pensions and health care.
- More resources are needed for the care and independent living of old people.
- A very young population needs schools now and jobs later.
Fewer births
- Japan's fertility rate has been below 1.5 since the mid-1990s: 1.2 in 2024
Fewer workers
- The population fell from 128 million in 2010 to 124 million in 2024, and the working-age share is shrinking
More elderly
- Almost 30% are 65 or over; pensions and health care cost more each year
Responses
- Raising the retirement age, more care robots, and letting in more foreign workers
The other end: In Niger the problem is the reverse: nearly half the people are children, so the country must pay for schools and health care now and create millions of jobs later.
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Why growth does not stop at once: When the fertility rate falls to replacement level, you might expect growth to stop. It does not: the number of women of reproductive age matters too.
Population momentum
- Population momentum: a population keeps growing even after the fertility rate falls.
- Growth depends on children per woman and on the number of women of reproductive age.
- A young structure (wide base) means many women will soon reach reproductive age.
- Even at replacement level, their many children keep births above deaths for decades.
- Growth slows only when the big young groups have grown old.
Real example: India's fertility rate was 1.96 in 2024, below replacement. But the young age groups born when fertility was 3 or 4 are now entering their twenties, so births still outnumber deaths.
Read the shape: Look for bars at ages 10-29 that are wider than the 0-4 bar: fertility has fallen, but the parents of the next twenty years are already born.
The same idea explains the world's future, and why some countries shrink.
Momentum both ways
- Momentum works in both directions.
- A population with few young women keeps shrinking even if fertility rises.
- Small young groups mean few future mothers, so births stay low for decades.
- Japan and South Korea face this negative momentum now.
Positive momentum: the world
- The UN tried a 'momentum' scenario: fertility at replacement from 2024
- Even so, the world grows from 8.2 to 9.6 billion by 2100
- The extra people come from today's large young groups
Negative momentum: Japan
- Few women are now in their twenties and thirties
- Even if fertility rose, births would stay low for decades
- The UN projects 124 million (2024) falling to 102 million by 2054
Remember it as: Count the mothers, not just the babies per mother.
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How this comes up: Paper 1: from a pyramid, outline issues for a country's future economic development [2]. Paper 2: explain the role of population momentum beside a pyramid [3], or calculate a dependency ratio.
Spain's age-sex pyramid for 2024 has a narrow base and is widest at ages 45-59. Its fertility rate is 1.2 children per woman, and 21% of its people are aged 65 or over.
Outline potential issues for the future economic development of Spain.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
The second shape asks you to explain momentum. Use the same three steps every time: define, link to the structure, then show the result.
The Philippines' fertility rate fell to 1.9 children per woman in 2024, below replacement level, but 28% of its people are under 15.
Explain the role that population momentum plays in population growth.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.