GeographyICSE Class 8 · Population Dynamics

Population Change, Composition and Population Pyramids (ICSE Class 8 Geography)

Updated 17 October 2026 · Draft, not yet fact-checked

A place's population changes through birth rate, death rate, immigration and emigration. Natural growth per 1,000 = birth rate - death rate. Composition describes a population by age, sex and residence (rural or urban); age-sex composition is shown on a population pyramid, which may be expanding (wide base), stationary or contracting (narrow base).

Understand Birth Rate, Death Rate, Composition and Population Pyramids

1. Factors that change population. Birth rate is live births per 1,000 people per year; death rate is deaths per 1,000 per year; immigration is people coming in; emigration is people leaving.

Natural growth (per 1,000) = birth rate - death rate. As a percentage = (birth rate - death rate) / 10.
Total change = (births - deaths) + (immigrants - emigrants).
Net migration = immigrants - emigrants; positive means a gain of people.

High birth rates are linked with early marriage, a wish for large families, low education (especially of women) and weak access to health care and family planning. Death rates have fallen because of medical care, vaccination, clean water, sanitation and better food supply.

2. Age composition. Three broad groups: young (0-14 years), working age (15-64; some sources 15-59) and old (65 and above; some sources 60 and above). Dependency ratio = (young + old) / working-age x 100. A high ratio means each worker supports many dependents.

3. Sex composition. In India the sex ratio is the number of females per 1,000 males; India recorded 943 in the 2011 Census. Many international sources use males per 100 females. A low ratio may result from a preference for sons and neglect of girls; male out-migration can raise the ratio in the villages they leave.

4. Rural and urban composition. Rural people mainly do primary work (farming, fishing, forestry, mining); urban people mainly do secondary and tertiary work. In India about 69 per cent lived in rural areas and 31 per cent in urban areas in 2011. Worldwide, more than half the people have lived in urban areas since about 2007.

5. Population pyramid. A graph with age groups on the vertical axis (youngest at the bottom), males on the left and females on the right; the length of each bar shows the number or percentage.

*Expanding:* wide base, narrow top; high birth rate and short life expectancy; a young, growing population (many developing countries, for example Nigeria).
*Stationary:* narrower base and nearly equal bars up to old age; low birth and death rates; little growth.
*Contracting:* base narrower than the middle; very low births and long life; an ageing, possibly shrinking population (for example Japan).

Uses: planning schools (wide base), jobs (large middle) and pensions and health care (wide top).

Birth Rate, Death Rate, Composition and Population Pyramids: key facts

Natural growth: $N a t u r a l g r o w t h p er 1, 000 = bi r t h r a t e - d e a t h r a t e ∣ P er ce n t a g e = (bi r t h r a t e - d e a t h r a t e) /10$
Total change: $C han g e = (bi r t h s - d e a t h s) + (immi g r an t s - e mi g r an t s) ∣ N e t mi g r a t i o n = immi g r an t s - e mi g r an t s$
Dependency ratio: $D e p e n d e n cy r a t i o = (y o u n g + o l d) / w or k in g - a g e x 100∣ U ni t : d e p e n d e n t s p er 100 w or k er s$
Pyramid types: Expanding wide base
Stationary straight sides
Contracting narrow base

Expanding	wide base
Stationary	straight sides
Contracting	narrow base

How to answer Birth Rate, Death Rate, Composition and Population Pyramids questions

For growth sums, write the formula, substitute, and attach a unit (per 1,000 or per cent).

1For total change add natural change and net migration, keeping signs correct.
2For a pyramid, look at the base first, then the middle, then the top.
3Say what the shape shows about birth rate, death rate and life expectancy.
4End with one planning use.

Birth Rate, Death Rate, Composition and Population Pyramids in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

A town's yearly change

Suppose a hill-station council expects 18,000 residents at the start of a year. During the year it counts 520 births and 310 deaths, and a new college and hotels bring in 1,150 people, while 430 residents leave for the plains.

Find the total change in population and the new population.

Try it first, then show the solutionSolution

Natural change = 520 - 310 = 210.
Net migration = 1,150 - 430 = 720.
Total change = 210 + 720 = 930; new population = 18,000 + 930 = 18,930.

Answer: Increase of 930; new population 18,930.

Memory hook: Births minus deaths, plus in minus out.

Tricks to remember Birth Rate, Death Rate, Composition and Population Pyramids

Short memory aids. Say each one aloud once, then use it on a question the same day.

BD gap
Birth rate minus Death rate is the natural growth rate.
Use it when: Growth sums.
Base tells the story
A wide base means many children (expanding); a narrow base means few births (contracting).
Use it when: Pyramid questions.
Females per 1,000 males
Indian sex ratio counts females per 1,000 males.
Use it when: Sex ratio.

Birth Rate, Death Rate, Composition and Population Pyramids: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Natural growth · 2 marks · Short answerBoard level

A country has a birth rate of 32 per 1,000 and a death rate of 9 per 1,000. Find its natural growth per 1,000 and as a percentage.

Try it first, then show the solutionSolution

Natural growth = 32 - 9 = 23 per 1,000.
As a percentage = 23 / 10 = 2.3 per cent.

Answer: 23 per 1,000, or 2.3 per cent.

Example 2: Meaning of terms · 2 marks · Short answerBoard level

Define (a) immigration and (b) emigration, and state which increases the population of a place.

Try it first, then show the solutionSolution

Immigration: people coming into a place to live.
Emigration: people leaving a place to live elsewhere.
Immigration increases the population of the place they enter.

Answer: Immigration adds people; emigration removes them.

Example 3: Population change · 4 marks · Long answerHarder board level

A district begins the year with 80,000 people. During the year there are 2,400 births, 800 deaths, 1,500 immigrants and 2,100 emigrants. Find (a) natural change, (b) net migration, (c) the population at the year end.

Try it first, then show the solutionSolution

(a) 2,400 - 800 = 1,600.
(b) 1,500 - 2,100 = -600 (net loss).
(c) Total change = 1,600 - 600 = 1,000; population = 80,000 + 1,000 = 81,000.

Answer: (a) +1,600 (b) -600 (c) 81,000.

Example 4: Dependency ratio · 3 marks · Short answerHarder board level

In a region, 30,000 people are aged 0-14, 60,000 are aged 15-64 and 6,000 are aged 65 and above. Find the dependency ratio and say what it shows.

Try it first, then show the solutionSolution

Dependents = 30,000 + 6,000 = 36,000.
Ratio = 36,000 / 60,000 x 100 = 60.
Each 100 working-age people support 60 dependents.

Answer: Dependency ratio is 60.

Example 5: Interpreting a pyramid · 4 marks · Long answerHOTS / competency

The bars of a country's pyramid are almost equal in length from the youngest group up to the oldest groups, with only a slight narrowing at the very top. (a) Name the type. (b) State what it shows about the birth and death rates. (c) Why will the country not need many more schools in the coming years, but will need more health care for the old?

Try it first, then show the solutionSolution

(a) Stationary (constant) pyramid.
(b) Low birth rate and low death rate, so the population grows slowly or not at all.
(c) The base is not widening, so the number of children stays steady and existing schools are enough; the large older groups will need more health care and pensions.

Answer: (a) Stationary (b) Low birth and death rates (c) Steady child numbers, growing old-age needs.

Where students lose marks in Birth Rate, Death Rate, Composition and Population Pyramids

The slips examiners see most often, and what to write instead.

Mistake: Wrong division for percentage
Birth minus death per 1,000 is converted incorrectly.
Wrong working
Growth = 23 per cent
Right working
Growth = 23 per 1,000 = 2.3 per cent
Do this: Divide the per-1,000 figure by 10 to get per cent.
Usually costs: 1 mark.
Mistake: Ignoring sign of net migration
Emigrants exceeding immigrants gives a negative figure.
Do this: Keep the minus sign and subtract from the total.
Usually costs: 1 to 2 marks.
Mistake: Describing a pyramid by shape only
No inference about birth rate or life expectancy is given.
Do this: State type, what it shows and one planning need.
Usually costs: 1 to 2 marks.
Mistake: Quoting the sex ratio as males per 1,000 females
The Indian definition is reversed.
Do this: Indian method: females per 1,000 males.
Usually costs: 1 mark.

Exam tips

Always show the formula line in numerical answers.
Label natural change, net migration and total change separately.
For pyramids, name the type first, then explain it.
Quote India's 2011 figures exactly: sex ratio 943; urban 31 per cent and rural 69 per cent.

Practice questions on Birth Rate, Death Rate, Composition and Population Pyramids

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
A pyramid with a narrow base and a wide middle is called:
(a) expanding
(b) contracting
(c) stationary
(d) rural
Hint
Few births.
Answer
(b) contracting.
Q2 · 1 mark · Very short answerBoard level
What is the sex ratio in the Indian method of measurement?
Hint
Per 1,000.
Answer
The number of females per 1,000 males.
Q3 · 2 marks · Short answerBoard level
State any two reasons why death rates have fallen in many countries.
Hint
Health and water.
Answer
Better medical care and vaccination; clean drinking water and sanitation; improved food supply (any two).
Q4 · 3 marks · Short answerHarder board level
A village has a birth rate of 28 per 1,000 and a death rate of 11 per 1,000, with a population of 20,000. Find the number of births and deaths in a year and the natural increase in numbers.
Hint
Per 1,000 means divide by 1,000.
Answer
Births = 28 x 20 = 560; deaths = 11 x 20 = 220; natural increase = 560 - 220 = 340 people.
Q5 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Many villages in migrant-sending areas show a rise in the sex ratio.
Reason (R): Large numbers of men migrate to cities for work, leaving women behind.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Who stays in the village?
Answer
(a).
Q6 · 4 marks · Long answerHarder board level
Compare the pyramids of a developing country such as Nigeria and a country such as Japan in terms of shape, birth rate and the main planning need.
Hint
Expanding against contracting.
Answer
Nigeria: expanding pyramid with a wide base, high birth rate and a young population; it needs schools, health care for children and jobs. Japan: contracting pyramid with a narrow base, very low birth rate and long life expectancy; it needs pensions, old-age health care and ways to maintain the workforce.
Q7 · 4 marks · Case-basedHOTS / competency
A town's population in 2015 was 4,00,000. By 2025 it had grown to 5,20,000. Natural increase accounted for 60,000 of the change. (a) Find the total change. (b) Find the contribution of net migration. (c) Suggest what this suggests about the town's economy.
Hint
Total change minus natural change.
Answer
(a) 520,000 - 400,000 = 120,000. (b) 120,000 - 60,000 = 60,000 people from net migration. (c) Half the growth came from in-migration, so the town offers jobs and services that attract people.
Q8 · 3 marks · Short answerHOTS / competency
Why does a high proportion of old people raise the dependency ratio, and why is it a concern for a government?
Hint
Think of workers supporting dependents.
Answer
Old people are mostly dependent on others, so the numerator of the ratio rises. Each worker supports more people, and the government must spend more on pensions and health care while fewer people pay taxes.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Birth rate definition?Show answer
Live births per 1,000 people in a year.
2.Natural growth formula?Show answer
Birth rate - death rate.
3.Three age groups?Show answer
Young (0-14), working age (15-64) and old (65 and above).
4.Pyramid with a wide base?Show answer
Expanding.
5.India's sex ratio in 2011?Show answer
943 females per 1,000 males.

Birth Rate, Death Rate, Composition and Population Pyramids: frequently asked questions

What is the difference between birth rate and fertility?

Birth rate counts births per 1,000 of the whole population; this chapter uses birth rate only.

Why do expanding pyramids occur?

High birth rates and short life expectancy keep the base wide and the top narrow.

What is net migration?

Immigrants minus emigrants.

Which sectors employ most urban people?

Secondary (manufacturing) and tertiary (services) activities.