Analysis guide
The Demographic Transition Model and Population Pyramids
Connect the five stages of the demographic transition model with changing birth rates, death rates, growth, and population-pyramid shape.
The demographic transition model (DTM) describes a broad shift from high birth and death rates to low birth and death rates. Population pyramids make the age-structure effects of that shift visible.
The model is best understood as a teaching framework. It summarizes a pattern observed in many populations, but it is not a law, a quality ranking, or a timetable every country must follow.
The five-stage version
| Stage | Birth rate | Death rate | Typical population change | Common pyramid tendency |
|---|---|---|---|---|
| 1 | High | High | Slow, volatile growth | Broad base, rapidly narrowing |
| 2 | High | Falling | Rapid growth | Very broad base |
| 3 | Falling | Low | Growth slows | Base begins to narrow |
| 4 | Low | Low | Slow or stable growth | More rectangular |
| 5 | Very low | Low | Natural decrease possible | Narrow base, older top |
No country today is a clean example of the historical first stage at national scale. Modern data and institutions also make current transitions different from those experienced by early-industrializing countries.
Stage 2: mortality falls first
When sanitation, nutrition, vaccination, and healthcare improve, deaths—especially child deaths—may fall before births do. More children survive, the base stays wide, and population growth accelerates.
The resulting pyramid often looks strongly expansive. Over time, its large young cohorts create population momentum.
Stage 3: fertility begins to fall
Birth rates decline as education, urbanization, child survival, access to contraception, economic conditions, and social expectations change. New cohorts become smaller relative to those just above them, narrowing the base.
The working-age share can rise during this period. Whether that becomes an economic dividend depends on jobs, health, education, and inclusion—not demography alone.
Stage 4: low birth and death rates
With both rates low, cohort sizes can become more even and the pyramid more column-like. But migration and past baby booms may create prominent bulges. “Stationary” shape does not necessarily mean a constant population.
Stage 5: ageing and possible natural decrease
Some versions add a fifth stage in which births remain below deaths. The base is narrow, median age rises, and older groups occupy a larger share. Population can still grow if net migration outweighs natural decrease.
Why we do not assign every country a DTM stage
A precise stage label can create false certainty. Large countries contain regions at different points; migration can separate age structure from natural change; wars, epidemics, and policy shifts can interrupt trends. Stage definitions also vary among textbooks.
Our profiles therefore publish the measurable ingredients—age shares, fertility, growth, median age, longevity, and projection direction—and let readers use the DTM as context rather than a verdict.
Explore the three common pyramid types or compare regional age structures to see the transition’s diversity.
Sources
Frequently asked questions
What are the stages of the demographic transition model?
A common five-stage version moves from high birth and death rates, through mortality decline and later fertility decline, toward low rates and in some versions natural decrease.
Is every country in one DTM stage?
The model is a broad framework, not a universal classification system. National averages can hide regional differences, migration effects, and reversals.
How does the population pyramid change during transition?
It often shifts from a broad triangular base toward a more rectangular and eventually top-heavy form as fertility falls and survival improves.