The Global Centre for Risk and Innovation (GCRI)
Populations change through births, deaths and migration: some are young and growing fast, others ageing and shrinking. These transitions shape labour supply, demand for schools and health care, pension systems and exposure to risk. This page sets out how demographic change unfolds, how it is measured and projected, and what evidence serves the governments that must plan for it.
GCRI · In development · service level R0
Demographic change is the shift in a population's size, age structure and distribution through births, deaths and migration. Falling fertility first raises the working-age share and later brings ageing, migration reshapes cities, and growing populations in hazardous places raise exposure. Projections carry uncertainty that widens over time.
For demographic transitions, in GCRI's spatial-intelligence reading, the map opens on population density and true-colour imagery with true colour from NASA GIBS, framed on Latin America and the Caribbean; every other NASA layer, live feed and forecast waits in the layer list.
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NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth
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For demographic transitions, in GCRI's spatial-intelligence reading, the map opens on population density and true-colour imagery with true colour from NASA GIBS, framed on Latin America and the Caribbean; every other NASA layer, live feed and forecast waits in the layer list.Satellite and model products as NASA publishes them, each with its own date; indicators, not assessments of any place; claim ceiling INTEGRATED.
Layers and dates
The working screen behind this subject: its structure, terms and states. Names are placeholders and values illustrative.
Demographic transitions · Urban ward 9 · Year 1
| Trust in neighbours | 59 | 64 | ▼ 1 |
| Trust in local authority | 36 | 42 | ▼ 6 |
| Reported discrimination | 12 | 9 | ▲ 1 |
Ageing, migration and population change. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
As fertility falls, the working-age share grows for a period, then the population ages. The timing differs greatly between countries.
More older people raise demand for health care, long-term care and pensions, while the working-age population that funds them may shrink.
Internal and international migration moves people toward cities and opportunity, changing local populations faster than births and deaths.
Growing populations in coastal cities, drylands and informal settlements increase the number of people exposed to hazards.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Total fertility rate | The average number of children a woman would have at current age-specific birth rates. |
| Demographic dividend | Potential economic growth from a rising working-age share of the population. |
| Dependency ratio | The ratio of people of non-working age to those of working age. |
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Total fertility rate | births per woman | annual | Vital registration and surveys | ESTIMATED |
| Life expectancy at birth | years | annual | Vital registration and models | ESTIMATED |
| Old-age dependency ratio | people aged sixty-five and over per hundred aged fifteen to sixty-four | annual | Population estimates | ESTIMATED |
| Net migration rate | per thousand population | annual | Population estimates | ESTIMATED |
| Urban population share | percent | annual | Population estimates | ESTIMATED |
| Population projections | people by age and sex | per revision | UN World Population Prospects | FORECAST |
The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.
Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| UN World Population Prospects | Population estimates and projections by age and sex | Open, CC BY 3.0 IGO |
| UN World Urbanization Prospects | Urban and rural population | Open, CC BY 3.0 IGO |
| Human Mortality Database and Human Fertility Database | Detailed mortality and fertility series for countries with good data | Open, CC BY 4.0 |
| National censuses and civil registration | Population counts and vital events | Licence per country |
| WorldPop | Gridded population estimates | Open, CC BY 4.0 |
Society and Human Development prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Ministries of planning and finance | How to prepare budgets and services for population change | Profiles; projections |
| Ministries of health and social affairs | How much care capacity and pension financing to plan | Demand projections |
| Urban and regional planners | Where population growth will need housing and services | Gridded population and urbanisation evidence |
Demographic transition describes the shift from high to low birth and death rates as societies develop. Countries are at different stages: some have growing, young populations, while others are ageing rapidly and some are shrinking. Population momentum means that age structure keeps driving growth or decline for decades after fertility changes, so many outcomes are already set in motion.
Ageing raises vulnerability to heat, infectious disease and disruption of care, and older people living alone are especially exposed. Migration responds to economic opportunity, conflict, family networks and environmental change; most migration is internal, from rural to urban areas, and environmental stress usually acts through livelihoods rather than as a single cause. Rapid urban growth can outpace housing and services, increasing informal settlement in hazardous places.
Care is a critical link. As populations age and families become smaller and more dispersed, the informal care that many older people rely on becomes less available, and care workers, often migrants, become essential to resilience in ageing societies.
Censuses and civil registration underpin demography; many countries have gaps in registration of births and deaths.
Projections follow fertility, mortality and migration assumptions; migration is the hardest to project.
Population grids combine census and imagery to locate people; accuracy varies with input quality.
Limits: projections are conditional on assumptions and become more uncertain further ahead and for smaller areas. Migration data are often incomplete, especially for irregular and temporary movement.
The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.