Demographic Transition Model (DTM)
1. Stage 1: High birth rate, high death rate, population fairly stable
2. Stage 2: Death rate decreases, birth rate remains high, population grows
3. Stage 3: Birth rate drops rapidly, death rate continues to decrease but more slowly, population still grows, but not quite as fast
4. Stage 4: Low birth rate, low death rate, birth rate can fluctuate depending on the economic situation
5. Stage 5: Birth rate falls below death rate, death rate increases slightly because of ageing population, population decreases unless immigration replaces the retired population