Cambridge O Level Economics: Population (2281)

This guide follows the Cambridge O Level Economics (2281) syllabus for examination in 2026, version 2. It covers section 5.3, Population (5.3.1 to 5.3.3). There are no tiers. The syllabus note requires you to interpret a pyramid; drawing one is not required. Every country and figure below is invented and illustrative, and none describes a real place.

Related pages: the revision notes, the practice questions, the Cambridge O Level Economics hub, the printable checklist, the economic development practice set and the free diagnostics.

What this unit covers

Section	What the syllabus asks	Where in this guide
5.3.1	Factors that affect population growth: birth rate, death rate, net migration, immigration and emigration	Section 1
5.3.2	How and why birth rates, death rates and net migration vary between countries	Section 2
5.3.3	The concept of an optimum population; effects of rising and falling population size; effects of changes in age and gender distribution; interpreting a population pyramid	Sections 3 to 5

Calculators may be used in the examination, so the arithmetic below is shown in full and you can check it.

1. Factors that affect population growth (5.3.1)

Population changes for two reasons.

• Natural change = births minus deaths.
• Net migration = immigration minus emigration.

Immigration is people moving into a country to live. Emigration is people leaving a country to live elsewhere. Total change in population = natural change + net migration.

Rates are usually given per 1,000 people:

• birth rate: divide births by the population, then multiply by 1,000
• death rate: divide deaths by the population, then multiply by 1,000
• natural increase per 1,000 = birth rate minus death rate
• growth rate (%) = total change ÷ opening population × 100

Worked example 1: a slowly growing country (Country K, illustrative)

Opening population 36,400,000. Births 509,600. Deaths 327,600. Immigrants 128,000. Emigrants 61,600.

Birth rate     = 509,600 / 36,400,000 x 1,000 = 14.0 per 1,000
Death rate     = 327,600 / 36,400,000 x 1,000 =  9.0 per 1,000
Natural change = 509,600 - 327,600            = +182,000  (5.0 per 1,000, 0.5%)
Net migration  = 128,000 - 61,600             =  +66,400
Total change   = 182,000 + 66,400             = +248,400
Growth rate    = 248,400 / 36,400,000 x 100   = 0.68%
Closing        = 36,400,000 + 248,400         = 36,648,400

Worked example 2: fast growth with net emigration (Country L, illustrative)

Opening population 9,600,000. Births 316,800. Deaths 105,600. Immigrants 9,600. Emigrants 28,800.

Birth rate     = 33.0 per 1,000     Death rate = 11.0 per 1,000
Natural change = +211,200 (2.2%)    Net migration = 9,600 - 28,800 = -19,200
Total change   = +192,000           Growth rate = 2.0%
Closing        = 9,792,000

Net migration here is negative, so it slows growth. Growth is still fast because the birth rate is far above the death rate.

2. Why growth differs between countries (5.3.2)

The syllabus asks how and why birth rates, death rates and net migration vary. Give a cause, then say which way the rate moves.

Birth rates

Factor	Chain of reasoning
Education of girls and women	More years in school and more paid work raise the opportunity cost of childcare, so women have fewer children and have them later.
Contraception and family planning	Greater access lets families choose family size, so the birth rate falls.
Infant mortality	Where many children die young, families have more children to be sure some survive. As infant mortality falls, so does the birth rate, usually after a lag.
Cost of raising children	In cities, housing and schooling cost more and children do not help on a farm, so families are smaller.
Old-age support	Where there is no state pension, parents rely on their children, which keeps the birth rate high.
Culture, religion and government policy	Attitudes to family size, marriage age and policies such as tax benefits for families push the rate up or down.

Death rates

• Healthcare and sanitation. Clean water, vaccination and more doctors cut deaths from disease.
• Food supply and income. Better nutrition raises resistance to illness.
• Conflict, famine and disease outbreaks raise the death rate sharply.
• Age structure. A country with an old population has many deaths each year even if healthcare is excellent. A rich country can therefore record more deaths per 1,000 than a poorer country full of young people. Make this point whenever the question asks why.

Net migration

• Push factors drive people out: unemployment, low wages, conflict, poor services.
• Pull factors draw people in: jobs, higher wages, better schools and hospitals, safety.
• Rules matter too. Entry limits, visa policy and the cost of travel change the flow.

A country with a high birth rate, a falling death rate and net emigration has a very different growth path from a country with a low birth rate and net immigration. Use the figures in the question to say which rate is doing the work.

3. Optimum population (5.3.3)

The optimum population is the size at which output per head reaches its maximum, for the land, resources, capital and technology the country has. Below that size the country is under-populated: more workers would lift output per head. Above it the country is over-populated: each additional worker adds less than the existing average, which drags the average down.

Worked example 3: locating the peak (Country T, illustrative)

Population (millions)	Total output (billions)	Output per head	Output added by the extra 6 million
6	72	12	n/a
12	204	17	132
18	360	20	156
24	456	19	96
30	480	16	24

Output per head = total output ÷ population (72 ÷ 6 = 12, 204 ÷ 12 = 17, 360 ÷ 18 = 20, 456 ÷ 24 = 19, 480 ÷ 30 = 16). It peaks at 20 when the population is 18 million, so 18 million is the optimum. At 30 million the country is over-populated: the last 6 million people add only 24 billion, which is 4 each and well below the average. At 6 million it is under-populated, as the next 6 million add 132 billion, which is 22 each.

The peak can move. Better technology, more machinery, a more skilled workforce or new trade routes raise output per worker and move the optimum up. Loss of farmland, exhausted mineral stocks or climate damage move it down. So a country can become less over-populated without any change in numbers.

4. Effects of rising and falling population size (5.3.3)

Whether a change is good or bad depends on where the country sits relative to its optimum.

Rising population

• Possible gains: more workers, a bigger home market so firms gain from selling more, more taxpayers, a wider range of skills.
• Possible costs: pressure on land, water and housing; congestion; more spending needed on schools and hospitals; unemployment if jobs do not grow as fast as the labour force; lower output per head if the country is already above its optimum.

Falling population

• Possible gains: less pressure on resources and the environment; output per head may rise if the country had been above its optimum.
• Possible costs: labour shortages, fewer taxpayers, weaker demand for housing and goods, school closures, and a smaller pool of young workers and entrepreneurs.

Worked example 4: output per head and population growth (Country V, illustrative)

Real GDP grows by 3.6% in a year and population grows by 2.4%.

Real GDP per head growth = 1.036 / 1.024 - 1 = 0.0117 = about 1.2%

A quick estimate is 3.6 − 2.4 = 1.2 percentage points. If GDP grew 2.0% while population grew 2.5%, then 1.020 / 1.025 − 1 = −0.49%, so output per head would fall even though total output rose. Population growth that outpaces output growth lowers average living standards.

5. Age and gender structure; reading a pyramid (5.3.3)

A population pyramid is a pair of horizontal bars. Age groups run up the middle, males on one side and females on the other. You must interpret one. You do not draw one.

Make three checks: how wide the base is (the young), how wide the middle is (the working-age group) and how wide the top is (the old). Then compare the left and right sides for gender.

Worked example 5: three pyramids as tables (illustrative, % of total population)

Age group	Country N males	Country N females	Country M males	Country M females	Country P males	Country P females
0-14	18	17	7	6	6	6
15-29	14	14	9	9	17	9
30-44	10	10	11	11	20	11
45-64	7	8	15	16	10	9
65+	1	1	7	9	5	7

Each # is about 4% of the population (males and females combined)

Country N (youthful)
65+    #
15-64  ################
0-14   #########             <- wide base

Country M (ageing)
65+    ####                 <- wide top
15-64  ##################
0-14   ###

• Country N: 35% are aged 0-14 and only 2% are 65 or over. The base is wide. The birth rate is high and life expectancy is probably modest. Many children means heavy spending on schools now and a large labour force in 15 years, which needs jobs.
• Country M: 13% are aged 0-14 and 16% are 65 or over. The base is narrow. Births are low and people live long. Spending on pensions and healthcare rises while the share of workers falls.
• Country P: males are 58% of the population and are heavily bunched at ages 15-44, while the base is narrow. This pattern fits a country that attracts male migrant workers. Check that a pyramid really shows this before you claim it.

Dependency (a reading aid; the syllabus does not name it). People aged 0-14 and 65 and over depend on those aged 15-64. Dependants as a share of the working-age group: Country N is 37 ÷ 63 = 59 per 100 workers. Country M is 29 ÷ 71 = 41 per 100. Country P is 24 ÷ 76 = 32 per 100. Country M has 71 ÷ 16 = 4.4 workers for each person aged 65 or over; Country N has 63 ÷ 2 = 31.5.

Effects of age structure

• Young population: school and child health costs; high future labour supply; risk of youth unemployment; a growing market for children’s goods.
• Ageing population: higher pension and healthcare spending; fewer taxpayers per pensioner, so taxes rise or services are squeezed; labour shortages that may push wages up; demand shifts to care, health and leisure services; pressure to raise the retirement age or encourage immigration.
• Gender imbalance: a shortage of women can lower future births; a shortage of men in the home area can leave families short of workers or income, though remittances from abroad may rise; some occupations may struggle to recruit.

Evaluation points: the effect depends on how fast the change is, on whether productivity is rising, on government policy and on the starting position relative to the optimum.

Common errors

• Writing birth rate as a total. It is per 1,000 people.
• Forgetting migration when finding total growth.
• Saying a high death rate always means poor healthcare. Check the age structure.
• Defining optimum population as the biggest population or the one with most total output. The test is output per head.
• Using a pyramid to say a country is poor or rich without evidence.
• Listing effects of an ageing population without a chain of reasoning to the government budget or the labour market.

Official syllabus

Cambridge O Level Economics (2281) syllabus for examination in 2026, version 2, published by Cambridge University Press and Assessment (Cambridge International Education). Section 5.3 covers Population. Check the official document at the exam board for the full wording.

Next, test yourself with the practice questions and check weak spots against the revision notes.