Methodology
How the edition was made: methods, the model card, the evidence cut and its age, the acceptance record and the glossary.
Contents
- ·Edition home
- ·Executive summary
- 1People and places change together
- 2Key findings
- 3Systems and sectors at baseline
- 4Risks and capability
- 5A heatwave that meets an ageing, dense and informally housed district
- 6Readings from the other desks
- 7The 2027 agenda
- 8Systems in depth
- AMethodology
- BData appendix
- CReferences and record
- ·Complete edition, for print
A.1Methods
The global baseline uses published values and four simple derivations. Each is shown in full so that any reader can reproduce it.
| No. | Derivation | Calculation | Result |
|---|---|---|---|
| (1) | China natural change in 2025 | 7.92 − 11.31 million | −3.39 million |
| (2) | Japan deaths per birth in 2024 | 1,605,298 ÷ 686,061 | ≈ 2.34 |
| (3) | Growth of built-up area per person, 1975 to 2025 | (63 − 43) ÷ 43 | ≈ 47 per cent |
| (4) | Gap between harmonised and national urban share, 2025 | 81 − 58 | 23 points |
| Strength | Definition |
|---|---|
| STRONG | a disruption in the source system has historically changed the target system’s service or output within one season, in more than one region |
| MODERATE | an effect is documented but buffered or slower |
| WEAK | an effect is plausible but not documented at global scale |
| Label | Rule |
|---|---|
| Reported | value as issued by its source, with year |
| Inferred | reasoned from cited evidence; never a measurement |
| Estimated | Nexus analytical value with stated method |
| Scenario | conditional on stated assumptions |
| Expert input | structured editorial judgement awaiting evidence |
A.2Model card, Human Systems Model v0
- Model ID
- MDL-SR11-HUMANSYSTEMS · v0.1
- Purpose
- represent human systems as people and places that change together and the mechanisms by which change spreads between housing, health, work, water, energy and public finance
- Family
- graph-based system of systems
- Inputs
- the cited sources of this edition; no proprietary data
- Method
- expert-specified coupling strengths (STRONG · MODERATE · WEAK) from assessments and analogue events
- Validation
- none yet, first validation against federation evidence in 2027
- Uncertainty
- qualitative; strengths are hypotheses, not measurements
- Domain of validity
- global scale; not for asset-, site- or country-level use
- Reproducibility
- strength table and sources published in this edition
20couplings
typed in v0
4strong
documented within one season
4moderate
documented, buffered
12weak
plausible, undocumented
A.3The baseline evidence cut
Every Nexus edition is published from a frozen evidence cut. The global baseline cut is documentary: it pins the exact edition of every source cited. Federation cuts begin with the first national Foundry cuts in 2027.
- Cut ID
- DC-STRATEGIC-HUMANSYSTEMS-GLOBAL-2026-B0
- Type
- baseline documentary cut
- Resolution policy
- pinned · as of 30 September 2026
- Sources pinned
- 42 cited sources, each at the edition and access date in the references
- Model runs
- none at baseline, analytical values are stated with their method
- Digest
- computed at freeze and recorded in the publication record
- Supersedes
- nothing, first cut of the series
- Superseded by
- the 2027 human systems annual cut
Lineage
- 01
source edition
- 02
pinned citation
- 03
finding
- 04
page
- 05
publication record
| Element | Baseline 2026 | 2027 global annual |
|---|---|---|
| Sources | cited global publications, pinned by edition | national, regional and sector cuts through one graph |
| Analysis | stated methods and editorial estimates | typed analysis specifications |
| Models | Human Systems Model v0 specification | model runs with receipts |
| Findings | twelve baseline findings | findings re-bound to federation evidence |
| Review | five passes scheduled | five passes on the exact digest |
A.4Evidence age and coverage
A 2026 global edition rests on evidence observed in many different years. This page shows each time base, so that no single year label hides older evidence.
| Indicator | Observed | Released | Cadence | Next release |
|---|---|---|---|---|
| World population projections | 2024 | Jul 2024 | biennial | next revision |
| City, town and rural split | 2025 | Nov 2025 | periodic | next urbanisation revision |
| Slum and informal settlement counts | 2022 to 2025 | Mar 2026 | annual | next SDG report |
| Informal employment | 2016 | Apr 2018 | periodic | no update bound |
| China births and deaths | 2025 | Feb 2026 | annual | early 2027 |
| Japan births and deaths | 2024 | Jun 2025 | annual | mid 2026 release |
| Heat-related deaths | 2012 to 2021 | Oct 2025 | annual | late 2026 |
| Internal displacement | 2024 | May 2025 | annual | May 2026 report |
| City climate finance share | 2024 | Nov 2024 | biennial | next report |
| EU population | 1 Jan 2025 | 2026 | annual | next release |
| System | Coverage | Thinnest dimension |
|---|---|---|
| Population and fertility | GOOD | neighbourhood-scale data |
| Urban form | GOOD | national city definitions |
| Housing and informality | PARTIAL | recent country series |
| Ageing and care | PARTIAL | care capacity |
| Heat and health | PARTIAL | urban age-specific data |
| Displacement | PARTIAL | movement into cities |
| City finance | THIN | common basis |
| Mobility and safety | THIN | city-level data |
| Field | Source that would fill it | Blocker |
|---|---|---|
| Fertility and household formation on one basis across countries | national statistics offices and UN DESA | definitions and timing differ; national releases not all retrieved |
| Neighbourhood-scale heat, age and housing data | city governments and national statistics offices | not published on a common basis |
| UNHCR global forced displacement totals from the report itself | UNHCR Global Trends 202425 | the report page returned an access error and the publication record gave no totals; figures come from search summaries |
| IDMC global internal displacement totals from the report itself | IDMC Global Report 202526 | the page counter showed no value; only the sub-Saharan Africa figure and share were read |
| Full text of the Lancet fertility forecast | GBD fertility collaborators24 | the journal page returned an access error; figures come from search summaries |
| Groundswell internal climate migration estimates from the report itself | World Bank Groundswell27 | the page returned not found; figures come from search summaries |
| Korea fertility series from the national office | Statistics Korea28 | only a quarterly news summary was read; annual figures come from search summaries |
| Data year for the road traffic death estimate | WHO road traffic fact sheet22 | the page states no data year |
| Data year for the 1.16 billion housing estimate | UN DESA Goal 11 page6 | the page says latest data (2026) and gives no period; it differs from the 1.12 billion in the 2025 report5 |
| Dhaka population in World Urbanization Prospects 2025 | UN DESA key messages and press release23 | the key messages give 37 million and the press release gives almost 40 million |
| Share of people aged 60 and over living in low- and middle-income countries in 2050 | WHO ageing fact sheet4 | the page gives both two thirds and 80 per cent |
| Capability rungs beyond monitoring and planning | governments, city networks and ministries | not reviewed |
A.5Evidence cards, two anchor sources
Issued by the UN Population Division, advance unedited version. Biennial. Role: binds DEM-001, DEM-002 and AGE-006. Coverage: 237 countries and areas. The summary was read in full text.
EVD-SR11-001
UN World Population Prospects 2024 summary of results1
Issued by the UN Population Division. Periodic. Role: binds URB-003 and URB-004. Coverage: 237 countries and areas and more than 12,000 cities. The key messages were read in full.
EVD-SR11-002
UN World Urbanization Prospects 20252
| Dimension | EVD-SR11-001 | EVD-SR11-002 |
|---|---|---|
| Completeness | national estimates for all countries; revised by country | harmonised definitions; national definitions kept alongside |
| Timeliness | about 1 year after the base year | about 1 year after the base year |
| Revision | advance unedited version; revised each cycle | new method; 2025 values not comparable to earlier national figures |
| Method transparency | probabilistic method published | methodological report published |
| External validation | peer and country review | country consultation |
Evidence cards to follow in 2027
A.6Publication acceptance record
Editorial self-check at evidence close. Every applicable item carries a disposition; the remaining items are review, approval and deposit.
| Group | Area | Items | Pass | N/A | Pending |
|---|---|---|---|---|---|
| D1 | Identity and scope | 8 | 8 | 0 | 0 |
| D2 | Source and data | 12 | 9 | 1 | 2 |
| D3 | Analysis and models | 12 | 3 | 8 | 1 |
| D4 | Findings and claims | 9 | 8 | 0 | 1 |
| D5 | Figures, tables, maps | 10 | 6 | 2 | 2 |
| D6 | Editorial and citations | 10 | 8 | 0 | 2 |
| D7 | Review and approval | 13 | 0 | 0 | 13 |
| D8 | Artefact and design | 12 | 7 | 0 | 5 |
| D9 | Registry and release | 9 | 0 | 0 | 9 |
Publication gate
- Conditions met
- 14 of 23 at evidence close
- Blocking problems
- none recorded
- Open conditions
- reviews, approval of the exact digest, deposit, registry pointer
Not applicable at baseline
- Model runs
- first runs in Q1 2027
- Maps
- plates in Q2 2027
- Waivers
- none
A.7Status words
| Status | What it means |
|---|---|
| Observed | Measured directly and published by the source. |
| Reported | Published statistics of an official or institutional source. |
| Declared | Stated by the body concerned; not independently measured. |
| Estimated | A Nexus estimate from cited evidence, with its method in Annex A. |
| Modelled | Produced by a stated model from cited inputs. |
| Inferred | Reasoned from cited evidence; not measured. |
| Forecast | A projection by the cited source. |
| Simulated | A simulation result under stated assumptions. |
| Scenario | A conditional statement under stated assumptions; never a prediction. |
| Expert input | Expert judgement, recorded with its basis. |
| Candidate | Proposed for a later edition; not yet evidence. |
| Evidence-quality levels (EQL 1 to 5) grade the source behind a value; they are not a score of the subject. | |
A.8How the edition is made, released and corrected
Every edition is built from a sealed evidence cut, reviewed under three keys, signed and deposited before any site shows it as published; corrections go to Nexus Standards as change proposals and feed the next cut.
| Step | What happens | Source |
|---|---|---|
| 01 Evidence arrives from the pillars | Foundry seals observations and indicator series, Universe hands over after-action and scenario findings, and contributions are screened at every gateway, including this site’s. | |
| 02 The cut is sealed | On the cut date the evidence is pinned under one identifier, so anyone can rebuild the edition from exactly what it was built on. | |
| 03 The edition is assembled | The edition is drafted from its template and content pack. Agents may draft; they never publish and never decide. | |
| 04 The keys turn | At the publisher of record the truth key comes first: every value is checked against its source or stated method before the meaning and capital keys turn. No edition moves on until every key has been turned by a named steward. | |
| 05 The gate opens | A named approver releases one exact digest of the edition; any change after this point is a new version, never a silent edit. | |
| 06 Signed and deposited | The PDF, the web edition and the data bundle are signed together with a manifest and an RO-Crate description, and deposited on Zenodo with a concept and a version DOI. | |
| 07 Published on its desk’s site | Only then does the edition show as published on its desk’s Reports site, and the Collection lists it as a part. | |
| 08 Corrections go to Standards | Method and correction findings go to Nexus Standards as change proposals; citations, corrections and new contributions feed the next evidence cut. |
A teaching model of the process, not a forecast and not a record of any run; dates and counts on this page come from the programme record. Sources: Reports governance at GCRI Canada (2026); Zenodo, repository of record for Reports deposits (2026).
Lifecycle, one state at a time: Draft, Computed, Evidence bound, Reviewed, Approved for release, Published, Corrected, Superseded. This edition is a draft.
A.9Glossary and abbreviations
| Term | Meaning |
|---|---|
| Baseline Edition | the inaugural annual edition that fixes the reference state for the series |
| WEFH+B | water, energy, food, health and biodiversity, the national nexus core |
| Coupling | a typed dependency through which one system transmits to another |
| Protection gap | the share of losses not covered by insurance |
| Capability ladder | LISTED → EXISTS → ADEQUATE → TESTED → DEMONSTRATED |
| EQL | evidence-quality level, 1–5 |
| Evidence cut | a frozen resolution of exact sources and versions |
| NNC · NLC · NWG | National Nexus Consortium · National Leadership Council · National Working Groups |
| Abbreviation | Expansion |
|---|---|
| DESA | Department of Economic and Social Affairs |
| GBD | Global Burden of Disease |
| IDMC | Internal Displacement Monitoring Centre |
| IDP | internally displaced person |
| ILO | International Labour Organization |
| IOM | International Organization for Migration |
| NBS | National Bureau of Statistics of China |
| SDG | Sustainable Development Goal |
| TFR | total fertility rate |
| UNFPA | United Nations Population Fund |
| UNHCR | United Nations High Commissioner for Refugees |
| WHO | World Health Organization |
A.10Technical annex
| Item | Annex | Contents | Status |
|---|---|---|---|
| A.1 | Indicator definitions | the global indicator set, with units and sources | IN THIS EDITION |
| A.2 | Coupling strengths | the twenty-cell matrix and its rationale | IN THIS EDITION |
| A.3 | Scenario specification | SCN-SR11-HEAT-01 assumptions and signposts | IN THIS EDITION |
| A.4 | Capability placements | rung evidence for fifteen functions | IN THIS EDITION |
| A.5 | Model diagnostics | first runs and validation | 2027 |
| A.6 | Sensitivity analyses | influence of coupling strengths | 2027 |
| A.7 | Regional notes | regional human-system cards | WITH REGIONAL EDITIONS |
| A.8 | Review statements | pass-by-pass review record | AT RELEASE |
A.1 · indicator definition: harmonised city
- Construct
- a contiguous settlement classed as a city under the Degree of Urbanization method
- Unit
- people and number of cities
- Method
- grid-based population and built-up data classified into cities, towns and rural areas
- Source
- UN DESA World Urbanization Prospects 20252
- Uncertainty
- modelled estimates; differ from national urban definitions
- Known limits
- minimum city size is 50,000 inhabitants; national definitions give a different share
Notes
Numbers are the edition’s reference numbers, so a note reads the same in every chapter. The full list, with every source and its licence, is in Annex C. Annex C, references
- 25UNVERIFIED, not opened: UNHCR (ed.), Global Trends Report 2024, June 2025 (123.2 million forcibly displaced at the end of 2024; 73.5 million internally displaced; 42.7 million refugees), taken from search-result summaries; the report page returned an access error. Observation year 2024. Accessed 2026-11-03.back
- 26UNVERIFIED, not opened: IDMC (ed.), 2025 Global Report on Internal Displacement (83.4 million internally displaced at the end of 2024; 45.8 million new displacements by disasters in 2024), taken from search-result summaries. Observation year 2024. Accessed 2026-11-03.back
- 24UNVERIFIED, not opened: GBD 2021 Fertility and Forecasting Collaborators, Global fertility in 204 countries and territories, 1950 to 2021, with forecasts to 2100, The Lancet 403, 2057 to 2099, 2024 (global rate 2.23 in 2021, about 1.83 in 2050 and about 1.59 in 2100), taken from search-result summaries; the journal page returned an access error. Observation year 2021. Accessed 2026-11-03.back
- 27UNVERIFIED, not opened: Clement, V. et al., Groundswell Part II: Acting on Internal Climate Migration, World Bank, 2021 (up to 216 million internal climate migrants by 2050), taken from search-result summaries; the World Bank pages returned not found. Observation year 2021. Accessed 2026-11-03.back
- 28UNVERIFIED, not opened: Statistics Korea (ed.), 2024 and 2025 birth statistics (total fertility rate 0.75 in 2024 and 0.80 in 2025, preliminary), taken from search-result summaries of news reports. Observation year 2025. Accessed 2026-11-03.back
- 22WHO (ed.), Road traffic injuries, fact sheet (page dated 20 July 2026; about 1.16 million deaths a year; 92 per cent in low- and middle-income countries; the page states no data year). World Health Organization, Geneva. Observation year 2026. Accessed 2026-11-03.back
- 6UN DESA (ed.), Sustainable Development Goal 11, facts and figures (latest data 2026: about 1.16 billion in slums, informal settlements or inadequate housing; 24.8 per cent of urban residents in slums in 2022; 53.6 per cent in sub-Saharan Africa). United Nations, New York. Observation year 2026. Accessed 2026-11-03.back
- 5United Nations (ed.), The Sustainable Development Goals Report 2025, Goal 11 (1.12 billion in slums or informal settlements; urban green space 19.5 per cent in 1990 and 13.9 per cent in 2020; one billion in riverine flood-prone areas, half in cities). United Nations Statistics Division, New York. Observation year 2025. Accessed 2026-11-03.back
- 2UN DESA Population Division (ed.), World Urbanization Prospects 2025: Summary of Results, ten key messages (November 2025). United Nations, New York. Observation year 2025. Accessed 2026-11-03.back
- 3UN DESA (ed.), press release on World Urbanization Prospects 2025, 18 November 2025 (cities hold 45 per cent of the world population; Dhaka given as almost 40 million). United Nations, New York. Observation year 2025. Accessed 2026-11-03.back
- 4WHO (ed.), Ageing and health, fact sheet (60 and over: 1.4 billion in 2030 and 2.1 billion in 2050; 80 and over 426 million in 2050; baseline 1 billion in 2020; page also gives two thirds and 80 per cent for the share in low- and middle-income countries). World Health Organization, Geneva. Observation year 2020. Accessed 2026-11-03.back
- 1UN DESA Population Division (ed.), World Population Prospects 2024: Summary of Results (advance unedited version, July 2024). United Nations, New York. Observation year 2024. Accessed 2026-11-03.back
- 15IDMC (ed.), 2025 Global Report on Internal Displacement (report page: sub-Saharan Africa a record 38.8 million internally displaced, around 46 per cent of the global total; the global counter showed no value). Internal Displacement Monitoring Centre, Geneva. Observation year 2024. Accessed 2026-11-03.back