Put birth and death rates on one graph over two centuries and a pattern appears in country after country. The American demographer Warren Thompson described it in 1929, and Frank Notestein and others developed it into the demographic transition model (DTM).
| Stage | Births | Deaths | Growth |
|---|---|---|---|
| 1 High stationary | high | high | slow |
| 2 Early expanding | high | falling fast | fastest |
| 3 Late expanding | falling | low | slowing |
| 4 Low stationary | low | low | slow or none |
| 5 Declining (added by some) | very low | low | negative |
Key idea
As countries develop, death rates fall first (better food, clean water, medicine), and birth rates fall later (cities, schooling, jobs for women, children surviving). The gap in between is when the population grows fastest.
Why it works
Death rates can fall quickly because nearly everyone wants to live longer, and vaccines or clean water spread fast. Birth rates depend on family choices shaped by culture and economics, which change more slowly. Families have many children where children work on farms and many die young; they choose fewer where children survive, cost more to raise and need long schooling.
Worked examples
Worked example: Placing a country
CBR 34 per 1,000, CDR 8 per 1,000. Which stage fits?
- Death rate is already low; birth rate is still high.
- RNI = (34 − 8) ÷ 10 = 2.6%: fast growth.
- High births with low deaths and fast growth is stage 2 (moving toward 3).
Answer: Stage 2.
Worked example: Another country
CBR 10, CDR 11. Which stage?
- Births are below deaths.
- Natural decrease of 0.1% a year.
Answer: Stage 5 (declining).
Common mistake
Students think the population grows fastest in stage 1, "when birth rates are highest." Growth depends on the gap between births and deaths, not on births alone. In stage 1 both are high, so the gap is small. Growth is fastest in stage 2, when deaths have fallen but births have not. Also remember that the DTM was built from the history of Europe and North America; countries may move through it faster, slower or differently, and it does not include migration.