Cambridge IGCSE Economics: Population and differences in development between countries (0455) – Revision Notes

These notes condense sections 5.3 (Population) and 5.4 (Differences in economic development between countries) of the Cambridge IGCSE Economics 0455 syllabus for examination in 2026. For full explanations and longer worked examples, use the study guide. Then test yourself with the practice questions. Other links: the Cambridge IGCSE Economics hub, the printable checklist and the free diagnostics. All names and figures are invented. The course is not tiered. You must interpret a population pyramid, not draw one.

Definitions to know

Term	Meaning
Birth rate	Births per 1,000 people per year
Death rate	Deaths per 1,000 people per year
Natural change	Births minus deaths
Immigration	People moving into a country to live
Emigration	People leaving a country to live elsewhere
Net migration	Immigration minus emigration
Optimum population	The population that gives the highest output per head
Under-population	Fewer people than the optimum; resources not fully used
Over-population	More people than the optimum; output per head falls
Productivity	Output per worker (or per hour)
Primary, secondary and tertiary sectors	Raw materials and farming; making goods and building; services such as retail, banking and transport

Formulas

Quantity	Formula
Birth rate	births ÷ population × 1,000
Death rate	deaths ÷ population × 1,000
Natural increase (%)	(births − deaths) ÷ population × 100
Net migration	immigration − emigration
Total change	natural change + net migration
Output per head	total output ÷ population
Output per worker	total output ÷ number of workers
Growth in output per head	(1 + GDP growth) ÷ (1 + population growth) − 1
Saving ratio	saving ÷ income × 100
Dependency ratio (a helpful measure; the syllabus does not name it)	(aged 0-14 + aged 65+) ÷ aged 15-64 × 100

5.3.1 and 5.3.2 Population growth and why rates differ

Method for a population-change question, in steps:

1. Find natural change: births − deaths.
2. Find net migration: immigration − emigration.
3. Add them for total change.
4. Divide by the opening population for a percentage; add to it for the closing population.

Small worked reminder (Country A, illustrative)

Opening population 5,000,000. Births 100,000. Deaths 40,000. Immigration 5,000. Emigration 15,000.

Birth rate = 100,000 / 5,000,000 x 1,000 = 20 per 1,000
Death rate = 40,000 / 5,000,000 x 1,000 = 8 per 1,000
Natural change = +60,000 (12 per 1,000)
Net migration  = 5,000 - 15,000 = -10,000
Total change   = +50,000 = 1.0%
Closing population = 5,050,000

Causes at a glance

Factor	Pushes it up	Pushes it down
Birth rate	Children as labour or old-age support; child deaths; limited contraception; low female education	Higher incomes; women in work and education; costly child-rearing; pensions
Death rate	Famine; epidemic; war; poor sanitation; many elderly people	Better healthcare, food, clean water, vaccination
Net migration	Wages, jobs and safety at home or abroad (pull); conflict and unemployment (push)	Entry controls; weak job market at the destination

Must-know distinctions

• Natural change is not the same as total change. Migration can reverse the sign.
• A rate is per 1,000. A number is a count.
• Low-income countries tend to have higher birth rates. A rich ageing country can still have a higher death rate than a poorer, younger one.
• Death rate falls first as healthcare improves. Birth rate falls later. Growth is fastest in between.

5.3.3 Effects of changes in population

Optimum population

Optimum = highest output per head. Check by working out output ÷ population in every row.

Small worked reminder (Country G, illustrative)

Population (millions)	Output (units, billions)	Output per head
4	20	5
8	56	7
12	96	8
16	112	7

The optimum is 12 million, with 8 units per head. At 16 million the country is over-populated. The optimum can rise with new technology, more capital or better skills.

Effects of size change

Change	Possible benefits	Possible costs
Population rises	Bigger workforce and market; more taxpayers	Pressure on land, housing, water; unemployment; lower output per head if over the optimum
Population falls	Less pressure on resources	Labour shortages; fewer taxpayers; falling demand

Age and gender: reading a pyramid

Read in this order: base (young), middle (workers), top (elderly). Then compare male and female bars in each band.

Shape	What it suggests	Effects
Wide base, narrow top	High birth rate, lower life expectancy	Spending on schools and child health; many future workers; need for jobs
Narrow base, wide top	Low birth rate, long life expectancy	Pension and healthcare bills; fewer workers per pensioner; labour shortage
Bulge in working ages	Many people of working age	Possible gain if there are jobs
More women at the top	Women live longer on average	More elderly women needing care
Fewer women than men at working ages	Perhaps inward migration of male workers or higher female death rates	Affects the labour supply and family formation

Small worked reminder: dependency ratio

Country H (illustrative): 28% aged 0-14, 65% aged 15-64, 7% aged 65+. Ratio = (28 + 7) ÷ 65 × 100 = 53.8. Roughly 54 dependants rely on each 100 people aged 15-64.

Evaluation checklist for population questions

• Compare with resources, capital and technology.
• Say whether the effect is short run or long run.
• Say who gains and who loses: firms, workers, taxpayers, the elderly.
• Mention government policy: education and training, pensions, retirement age, family support, migration rules.

5.4.1 Differences in development

Factor	Cause of the gap	Impact
Income	Low productivity, low investment	Poor housing, diet, health and schooling
Productivity	Little capital, weak skills, poor health	Low wages and low output
Population growth	Falling death rate with high birth rate	Output per head grows slowly; more demand for schools and food
Sector size	Most workers in low-value primary production	Lower income; volatile raw-material prices
Saving and investment	Low income leaves little to save	Little capital, so low productivity
Education	Not enough schools, teachers or money	Low skills and poor use of technology
Healthcare	Few clinics, weak sanitation	Illness, lost workdays, short working life

Small worked reminder: growth per head

GDP growth 4.0%, population growth 3.0%: 1.04 ÷ 1.03 − 1 = 0.97% a year. Saving ratio: saving 35 out of income 500 gives 7%. Output per worker: output 90 from 30 workers gives 3 each.

Evaluation chain: the income cycle

Low income → low saving → low investment → low productivity → low income. Education, healthcare, investment and lower population growth can each break the cycle. No single measure always works best. Averages hide inequality.

Quick self-test

1. A country has immigration of 25,000 and emigration of 40,000. Find net migration.
2. A town of 300,000 people has 6,000 births. Find the birth rate.
3. A country of 450,000 people has 2,700 deaths. Find the death rate.
4. Give one reason a rich country can have a higher death rate than a poorer one.
5. A country has 20% aged 0-14, 70% aged 15-64 and 10% aged 65+. Find the dependency ratio, to 1 decimal place.
6. Output is 48 billion units and there are 8 million workers. Find output per worker.
7. The same output of 48 billion units is shared among 12 million people. Find output per head.
8. Primary workers are 8% and secondary workers 24%. What is the tertiary share?
9. Define optimum population.
10. State one reason low saving keeps income low.
11. GDP grows 4% and population 3%. Find the growth in output per head to 2 decimal places.

Answers

1. 25,000 − 40,000 = −15,000 (net emigration).
2. 6,000 ÷ 300,000 × 1,000 = 20 per 1,000.
3. 2,700 ÷ 450,000 × 1,000 = 6 per 1,000.
4. A large share of elderly people raises deaths even where healthcare is good.
5. (20 + 10) ÷ 70 × 100 = 42.9.
6. 48 billion ÷ 8 million = 6,000 units.
7. 48 billion ÷ 12 million = 4,000 units.
8. 100 − 8 − 24 = 68%.
9. The population size that gives the highest output per head, given the country’s resources and technology.
10. Low saving funds little investment, so capital and productivity stay low.
11. 1.04 ÷ 1.03 − 1 = 0.97%.

Where marks are usually lost

• Using a count where a rate is asked, or leaving out “per 1,000”.
• Ignoring emigration, or subtracting in the wrong order.
• Saying “more people means more output” without comparing with resources and capital.
• Naming the optimum as the largest population, not the highest output per head.
• Describing a pyramid without reading all three parts: base, middle and top.
• Giving a cause without the impact on income, productivity or living standards.
• Writing an evaluation that only repeats the points made earlier, with no judgement or condition.
• Calling a fast-growing GDP a rise in living standards when population grew just as fast.

Official syllabus

Cambridge IGCSE Economics 0455 syllabus for examination in 2026, published by Cambridge International, sections 5.3 and 5.4.