8.1.4—Global population growth models
- Syllabus
- First assessment 2026
- Objective
- 8.1.4
- Level
- HL
Projection Means ‘If’
The global human population has followed a rapid growth curve, but future projections are conditional scenarios rather than fixed predictions.
UN high, medium and low scenarios diverge mainly because different fertility assumptions compound across generations; mortality and migration assumptions also affect the path.
If fertility falls faster than assumed, the population path can move below an earlier medium scenario even though current population is unchanged.
Read each curve's fertility, mortality, migration and time assumptions, and treat the spread as evidence of uncertainty.
The middle scenario is not guaranteed, and uncertainty does not make every scenario equally plausible.