8.1.8—Demographic transition model

DTM stages describe how birth and death rates change; the gap between those rates, not the stage label, determines whether population grows, stabilizes or declines.

Stage 1 has high births and deaths; in stage 2 deaths fall first, stage 3 births fall, stage 4 both are low, and stage 5 may have births below deaths. Use the rate sequence to explain the curve.

When deaths drop from 30 to 10 per 1,000 while births stay at 35, the gap widens and growth accelerates; later, falling births narrow the gap.

Stage 2 pattern: the death rate has fallen first, so the positive gap is large.

DTM stages are a generalized pattern, not a universal timetable every country follows identically.