GCRI · Society and Human Development
Demographic transitions
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.
Demographic transitions in seven parts.
- 01The questionDemographic transitions: how the risk develops
- 02Across the domainsPopulation change shifts demand in every domain
- 03IndicatorsWhat is measured, and how well
- 04SourcesWhere the evidence comes from
- 05DecisionsWho decides, and what the evidence serves
- 06Core questionsThe questions experts ask
- 07MechanismsFertility, mortality and movement
Demographic transitions: how the risk develops.
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.
Falling fertility changes age structure
As fertility falls, the working-age share grows for a period, then the population ages. The timing differs greatly between countries.
Ageing raises care needs
More older people raise demand for health care, long-term care and pensions, while the working-age population that funds them may shrink.
Migration reshapes populations
Internal and international migration moves people toward cities and opportunity, changing local populations faster than births and deaths.
Demography shapes exposure
Growing populations in coastal cities, drylands and informal settlements increase the number of people exposed to hazards.
People and exposure in Latin America and the Caribbean.
Population density, night lights and daytime surface heat over Latin America and the Caribbean, from NASA GIBS. Each layer carries its own date.
The interactive map needs JavaScript; the layer list and sources are below.
Layers 3
People and exposure, for this page
About this layer
- Evidence
- Estimated
- Source
- Gridded Population of the World v4.11 (NASA SEDAC (CIESIN, Columbia University))
- Provider
- NASA SEDAC (CIESIN, Columbia University)
- Licence
- CC BY 4.0
- Vintage
- null; Census-based estimate, static (2020)
- Resolution
- about 1 km grid
- Uncertainty
- Census-based estimate of people per square kilometre in 2020, shown as exposure context; not a count of people affected by any hazard.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed
- Source
- VIIRS Black Marble (VNP46A2) (NASA LAADS DAAC)
- Provider
- NASA LAADS DAAC
- Licence
- NASA open data
- Vintage
- daily; Satellite radiance, corrected for moonlight and atmosphere
- Newest at build
- 2026-10-12
- Resolution
- about 500 m grid
- Uncertainty
- Satellite night-time radiance for the date shown; lights are a proxy for electricity use and outages, not a measurement of supply or access.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (persistent cloud still leaves gaps)
- Source
- VIIRS NOAA-20 Level 3, 8-day (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- 8-day; Satellite 8-day composite; persistent cloud still leaves gaps
- Newest at build
- 2026-09-14
- Resolution
- about 1 km grid
- Uncertainty
- Satellite skin temperature of the ground over the 8 days ending on the date shown, a heat exposure indicator; not air temperature, heat index or a heat warning.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed
- Source
- VIIRS NOAA-20 corrected reflectance (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite image
- Newest at build
- 2026-10-14
- Resolution
- about 250 m grid
- Uncertainty
- Satellite image. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Modelled (latest year GIBS publishes)
- Source
- MODIS Terra and Aqua land cover (MCD12Q1) (NASA LP DAAC)
- Provider
- NASA LP DAAC
- Licence
- NASA open data
- Vintage
- yearly; Satellite classification; latest year GIBS publishes
- Newest at build
- 2024-01-01
- Resolution
- about 500 m grid
- Uncertainty
- Satellite land cover classes for the year shown, including croplands; a classification with known errors, not a farm register.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (clouds leave gaps)
- Source
- MODIS Terra EVI (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite index; clouds leave gaps
- Newest at build
- 2026-10-13
- Resolution
- about 250 m grid
- Uncertainty
- Satellite vegetation index for the 8 days to the date shown, a habitat condition indicator; not a measure of species or biodiversity.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
Keyboard, with the map focused
Hold Ctrl or ⌘ and scroll to zoom
Latest available
NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth
Loading the latest NASA imagery.
Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.
People and exposure, framed on Latin America and the Caribbean.Satellite and model products as NASA publishes them, each with its own date. They are indicators, not assessments of any place.
Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · NASA EONET · CIESIN/Columbia, NASA SEDAC HBASE · NASA JPL OPERA DIST-ALERTSources and licences
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Center for International Earth Science Information Network (CIESIN), Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11. NASA Socioeconomic Data and Applications Center (SEDAC). Licensed under CC BY 4.0. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). doi:10.7927/H49C6VHW. CC BY 4.0
- VIIRS Black Marble night-time lights, NASA Goddard Space Flight Center; distributed by the NASA Level-1 and Atmosphere Archive and Distribution System (LAADS DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- MODIS land products (vegetation indices, gross primary production, land cover), NASA LP DAAC and LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). Cite as: NASA/METI/AIST/Japan Spacesystems and U.S./Japan ASTER Science Team (2019). ASTER Global Digital Elevation Model V003. doi:10.5067/ASTER/ASTGTM.003. NASA open data
- Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
- © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). ODbL
- Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
- Live events: NASA Earth Observatory Natural Event Tracker (EONET); events are indicative and keep their original source links.
- Live: NASA EONET Events are indicative, not authority warnings.
- Context: CIESIN/Columbia, NASA SEDAC HBASE. Center for International Earth Science Information Network (CIESIN), Columbia University, and NASA Socioeconomic Data and Applications Center (SEDAC): Global Human Built-up And Settlement Extent (HBASE) 2010; Seto, Guneralp and Hutyra 2012, Global Grid of Probabilities of Urban Expansion to 2030; Global Urban Heat Island (UHI) Data Set, 2013.
- Observed (EO): NASA JPL OPERA DIST-ALERT (contains modified Copernicus Sentinel data 2026). We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- NASA GIBS: We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- Air quality forecast, 5 days, PM2.5 (CAMS via Open-Meteo): Contains modified Copernicus Atmosphere Monitoring Service information 2026.
- Weather data by Open-Meteo.com (https://open-meteo.com/), licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).
- Optional layers (9 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.
Layers and dates
- Population density, 2020: Population: CIESIN, Columbia University, Gridded Population of the World v4.11 (2018), NASA SEDAC, CC BY 4.0 · static
- Night-time lights, daily: VIIRS Black Marble (VNP46A2), NASA LAADS DAAC · 12 Oct 2026
- Land surface temperature, day, 8-day composite: VIIRS NOAA-20 Level 3, 8-day, NASA LANCE · 14 Sep 2026
- True colour: VIIRS NOAA-20 corrected reflectance, NASA LANCE · 13 Oct 2026
- Land cover type (IGBP), yearly: MODIS Terra and Aqua land cover (MCD12Q1), NASA LP DAAC · 2024
- Enhanced vegetation index, rolling 8 days: MODIS Terra EVI, NASA LANCE · 13 Oct 2026
Population change shifts demand in every domain.
Findings are designed for the Foresight Outlook series. World Population Prospects 2024 provides probabilistic projections; ranges are reported, not single numbers.
- Sub-national projections.
- Migration data.
Social protection and cohesion.
The screen a team would use to follow this subject: its measures, states and decisions. Names are examples and values are illustrative.
Social protection and cohesion
Demographic transitions · Urban ward 9 · Year 1
Coverage by quintile
Cohesion survey
| Trust in neighbours | 59 | 64 | ▼ 1 |
| Trust in local authority | 36 | 42 | ▼ 6 |
| Reported discrimination | 12 | 9 | ▲ 1 |
What is measured, and how well.
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 |
Model demographic transitions as a system. Run the cascade.
Assembled from the Nexus Standards area profile Societal and information risk standards: the hazards it names, the systems and sectors that carry the loss, the controls that dampen it and the data that observe it. Choose the components, pick an initiating hazard and step through the cascade. The Map view places the run on an example geography with open data. Every coupling weight is a stated assumption you can change. A teaching model, not a forecast, an assessment or a certification. To model a place of your own choosing, open the full System Builder.
Hazards
- Civil unrest
- Supply-chain disruption (set off downstream)
- Currency crisis (set off downstream)
Systems and couplings
Controls
NS-0Constitution and principlesNS-9Contextual UNIs (deployments, instances, programme instances)NS-11Verification and monitoring (evidence, attestations, zero-trust conformance observation)NS-12Software, model and AI/ML artefacts (supply chain, model cards, dataset sheets)NRS-H117Hazard family: Social cohesion and atrocity risk (NHS-1 soc.cohesion)NRS-X7Information integrity and public trustNRS-D2Society, inclusion and human development riskNRS-H52Hazard family: Information-integrity attacks (NHS-1 cyber.integrity)NRS-H79Hazard family: Mental health crises (NHS-1 health.mental)NRS-H59Hazard family: Economic shocks and governance failure (NHS-1 soc.economic)
Observation
- WorldPop gridded population (listed for reference)
- World Bank Open Data and World Development Indicators API (listed for reference)
- Global SDG Indicators Database (listed for reference)
- Number of deaths, missing persons and directly affected persons attributed to disasters per 100,000 population
- Proportion of people living below 50 per cent of median income
- Number of countries that adopt and implement guarantees for public access to information
Example geography
- The Horn of Africa: 253 hexagonal cells
- Night lights tonight, outages (VIIRS Day/Night Band), NASA GIBS
Where the evidence comes from.
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 |
How demographic transitions is modelled, measured and tested.
The model, its assumptions, its data and its uncertainty, in the form a scientist or engineer would check. Structures follow published methods. The values drawn are illustrative, not findings.
System model
The couplings between the systems in demographic transitions: signs of influence, a reinforcing and a balancing loop, and cross-links where stress jumps.
Who decides, and what the evidence serves.
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 |
Outputs this topic produces
- Demographic profiles and scenario comparisons
- Exposure analyses combining population growth and hazards
- Care and pension demand projections with uncertainty
- Evidence notes for national planning
The questions experts ask.
- How will the size, age structure and distribution of a population change over coming decades?
- How does ageing change vulnerability to heat, disease and isolation?
- Where is migration and urban growth concentrating people, and are services keeping pace?
- How do demographic shifts affect labour markets, pensions and care systems?
- How do hazards and climate change influence migration decisions?
Fertility, mortality and movement.
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.
Projection and its uncertainty.
Population counts
Censuses and civil registration underpin demography; many countries have gaps in registration of births and deaths.
Cohort-component models
Projections follow fertility, mortality and migration assumptions; migration is the hardest to project.
Gridded population
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.
How it is studied, and what the methods cannot say.
- 01Social and behavioural scienceSurvey design for hard-to-reach groups · Qualitative and participatory researchApplied here
- 02Spatial statistics and geostatisticsSmall-area poverty estimation · Vulnerability and hazard overlayApplied here
- 03EconometricsPoverty dynamics with panel data · Price shock incidence · Inequality decompositionApplied here
Where this page’s references lead.
The bodies and documents this page is read against. Status and editions change; each link goes to the issuing body.
Questions and answers.
What is the demographic dividend?
What is the old-age dependency ratio?
How reliable are population projections?
Is a population projection a forecast?
Does climate change cause migration?
Why does ageing matter for risk?
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