Key Idea: Most marks in topic 8.1 come from calculating population change and the demographic transition model. Then learn policies and indirect management, and at HL the dependency ratio and momentum.
1. Measuring change (most marks)
- NIR (%) = (CBR − CDR) ÷ 10. Always give the unit: % or per 1000.
- Doubling time = 70 ÷ growth rate (%): Niger grows about 3.3% a year, so it doubles in about 21 years.
- Japan, 2024: births 5.7 and deaths 13.3 per 1000, so NIR = −0.76% and it is shrinking.
2. The demographic transition model
- Stage 2: the death rate falls (food, vaccines, clean water) but births stay high, so growth is fast.
- Stage 3: the birth rate falls (school, contraception, city life). Stage 4: both low, about 10 per 1000.
- Stage 5: deaths exceed births: Germany since 1972, Japan since 2007.
3. Policies and HL ideas
- Direct policies: China's one-child policy (1980-2015); Singapore's Baby Bonus (since 2001).
- Indirect: educate girls and give women jobs. In Kerala about 92% of women read and have about 1.8 children.
- At HL: the dependency ratio, population momentum, stress on Earth systems and environmental migration.
How it is examined:
| Question | How to score |
|---|---|
| [1] Calculate an NIR or a doubling time | NIR = (CBR − CDR) ÷ 10; doubling time = 70 ÷ NIR %. Show working and the unit. |
| [4] Distinguish CBR from NIR or from TFR | CBR is births per 1000 people; NIR takes away deaths; TFR is children per woman. |
| [1] to [3] Place a country on the DTM | Quote its birth and death rates or pyramid shape, then name the stage. |
| [2] to [3] Suggest how a pyramid will change | Wide base: growth ahead. Narrow base: ageing. Give the reason. |
| [7] Explain how policies raise or lower growth | Direct (laws, money) and indirect (school, jobs), with named countries. |
| [9] To what extent can policies stabilise population? | Successes, failures and side effects, then a judgement. |
| [3] Explain why growth continues after fertility falls | Momentum: many young adults have children, so births still beat deaths. |
Key terms, one line each:
| Term | In one line |
|---|---|
| Crude birth rate (CBR) | live births per 1000 people per year |
| Crude death rate (CDR) | deaths per 1000 people per year |
| Natural increase rate (NIR) | the birth rate minus the death rate, per 1000 or as a percentage |
| Total fertility rate (TFR) | the average number of children a woman has in her lifetime |
| Doubling time | the years a population takes to double at its present growth rate |
| Dependency ratio | people aged 0-14 and 65+ compared with people aged 15-64 |
| Population momentum | growth that goes on after fertility falls, because many young adults are having children |
Last-minute check: answer, then tap to see.
Japan, 2024: 0-14 = 11.4%, 65+ = 29.8%. What is the dependency ratio? 41.2 ÷ 58.8 x 100 = about 70.
Why is India still growing with a TFR of 1.96? Momentum: many young adults born when fertility was 3 or 4 are now having children.
Why did Singapore reverse its policy in 1987? Births fell below replacement, so it switched to 'Have three or more if you can afford it'.
Did Singapore's Baby Bonus work? No: it began in 2001, yet the TFR fell to 0.97 in 2023.
India's total fertility rate was 1.96 in 2024, below replacement, yet the UN projects its population will keep growing until about 2060. Explain why a population can keep growing after its fertility rate falls below replacement.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Exam tips
- For a calculation, write the formula, show the working and give the unit.
- Say 'a high birth rate of 38 per 1000', not just the number.
- In stage 2 the death rate is falling, not yet low.
- For a [9] on policy, weigh direct and indirect policies and their side effects, with countries.