How is population data gathered, and how do the Demographic Transition Model and population pyramids show how a country's population changes?
How population data is gathered by census and the problems of collecting it in developed and developing countries; the Demographic Transition Model; and the use of population pyramids to show and explain a country's age and sex structure.
An SQA National 5 Geography answer on population, covering how population data is gathered by census, the problems of collecting it in developed and developing countries, the Demographic Transition Model, and how population pyramids show a country's age and sex structure.
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What this dot point is asking
The SQA wants you to explain how population data is gathered (mainly by census) and the problems of collecting it in developed and developing countries, to describe the Demographic Transition Model (DTM), and to use and explain population pyramids that show a country's age and sex structure.
Gathering population data
Governments use this data to plan services such as schools, hospitals, housing and transport.
Problems of collecting data
The difficulties are very different in developed and developing countries.
The Demographic Transition Model
The Demographic Transition Model (DTM) shows how a country's birth rate, death rate and total population change as it develops, in five stages:
- Stage 1 - high birth rate and high death rate; population low and steady (few countries today).
- Stage 2 - death rate falls (better food, water and medicine) while birth rate stays high; population grows fast (many developing countries).
- Stage 3 - birth rate falls (family planning, women working, fewer needed for farm labour); population still grows but more slowly.
- Stage 4 - low birth rate and low death rate; population high and steady (developed countries).
- Stage 5 - birth rate falls below death rate; population begins to fall and age.
Population pyramids
A population pyramid is a bar graph showing the percentage of males and females in each age group (males on the left, females on the right):
- A developing country has a wide base (high birth rate) and a quickly narrowing top (high death rate, low life expectancy), with steep concave sides from high infant mortality.
- A developed country has a narrow base (low birth rate) and a much wider top (long life expectancy), giving a more rectangular shape with many elderly people.
Pyramids show problems too: a wide base means pressure on schools and jobs; a wide top means pressure on pensions and health care.
Examples in context
Example 1. The UK at Stage 4 or 5. Low birth and death rates give the UK a roughly rectangular pyramid with a growing elderly population, creating pressure on pensions and health care.
Example 2. Niger at Stage 2. A very high birth rate gives Niger a wide-based pyramid with rapid population growth, putting pressure on food, schools and jobs.
Try this
Q1. State how often most countries take a census. [1 mark]
- Cue. About every ten years.
Q2. What does a wide base on a population pyramid show? [1 mark]
- Cue. A high birth rate (a developing country).
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 style5 marksExplain the problems of collecting accurate population data in a developing country.Show worked answer →
A 5-mark Explain answer wants several developed reasons, so give a range of problems and link each to why it makes data inaccurate.
Many people live in remote rural areas with no roads, so census collectors find it hard to reach them and some are missed altogether.
High rates of illiteracy mean many people cannot read or fill in a census form, so answers may be wrong or left blank.
Fast-growing shanty towns have no proper addresses and a constantly changing population, so people are easily missed or counted twice.
A census is very expensive, so a poor government may not be able to afford to run one often or to train enough collectors, leaving data out of date.
Some people distrust the government or do not speak the official language, so they avoid the census or misunderstand it. Markers reward each clear, separate problem (remoteness, illiteracy, shanty towns, cost, language and distrust) linked to inaccurate data.
SQA N5 style4 marksDescribe and explain the shape of the population pyramid of a developing country.Show worked answer →
"Describe and explain" needs both the shape and the reasons, so pair each described feature with why it happens.
The pyramid has a very wide base, because the birth rate is high: families have many children for farm labour and because of limited family planning.
It narrows quickly towards the top, because the death rate is high and life expectancy is low, so few people live to old age.
The sides have steep, concave slopes, showing that many children die young (high infant mortality) so each age group is much smaller than the one below it.
There is only a small number of elderly people at the top, because of poor health care and shorter lives. Markers reward each described feature (wide base, rapid narrowing, few elderly) matched with a clear reason (high birth rate, high death rate, high infant mortality).
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Sources & how we know this
- National 5 Geography Course Specification (C833 75) — SQA (2025)
- National 5 Geography - Course overview and resources — SQA (2025)