Urban Informality: A Billion People Living Outside the Map

Informal settlements—variously called slums, favelas, barrios, or townships—are not aberrations. They are the primary mode of urbanization in the Global South, housing an estimated 1 billion people who build their own shelter on land they do not formally own, connect to water and electricity through self-organized networks, and create economic livelihoods outside regulated markets.

These communities are invisible to official data systems—absent from census counts, cadastral maps, and municipal service plans. Yet they are among the most densely populated, economically productive, and socially resilient urban spaces in the world.

Why It Matters

By 2050, an additional 2 billion people will live in cities, mostly in Africa and South Asia, where formal housing markets cannot remotely keep pace with demand. Informal settlements will absorb much of this growth. How governments respond—with bulldozers or with upgrading; with eviction or with inclusion—will determine the quality of life for billions and shape the trajectory of entire nations.

The Research Landscape

Bulldozer Urbanism in Accra

Okwei and Adjaison (2025), with 3 citations, document state-led evictions of informal settlement residents in Accra, Ghana, using Cernea's Impoverishment Risks and Reconstruction framework. Evictions—justified by "urban modernization" and "beautification"—destroy established communities, livelihoods, and social networks. Relocated residents face worse outcomes on every dimension: longer commutes, lost income, disrupted children's education, and severed social ties. The study demonstrates that demolition without adequate resettlement is not urban planning—it is state-inflicted impoverishment.

Participatory Data for Inclusion

Mangara and Dorasamy (2025) argue that the exclusion of informal settlements from official data systems is itself a form of governance violence. In South Africa, where one in four urban residents lives informally, they develop participatory data collection methodologies where community members co-produce the maps, surveys, and assessments that formal planners use. This approach simultaneously generates accurate data and builds community capacity for engagement with municipal governance.

Community-Led Flood Adaptation

Bhanye (2025), with 16 citations, reviews community-based flood adaptation in informal settlements across the Global South. Informal settlements are disproportionately located in flood-prone areas—riverbanks, coastal lowlands, drainage basins—because these are the only unoccupied land accessible to the poor. Community-led approaches (drainage construction, flood warning systems, elevated building techniques) are often more effective and sustainable than top-down interventions because they build on local knowledge and maintain community ownership.

Global Scale Estimation

Boanada-Fuchs and Samper (2024), with 32 citations, provide the most comprehensive global estimate of informal settlement size and location. Analyzing city-level slum maps across 30 cities, they estimate nearly 1 billion slum residents in 2015, projecting 380 million more by 2030. A key finding: only half of all slums are located within the administrative borders of cities—meaning municipal planning processes systematically miss settlements beyond their jurisdictional boundaries, and shifting urbanization trends mean informality will remain a defining feature of 21st-century cities.

Informal Settlement Governance Approaches

What To Watch

Satellite-based mapping combined with AI is enabling automated detection and monitoring of informal settlement growth in near-real-time, providing governments with the data needed for proactive rather than reactive planning. The concept of "hybrid formality"—where settlements maintain informal social organization while accessing formal services through negotiated agreements—is emerging as a pragmatic alternative to the false binary of formal/informal.

Informal settlements—variously called slums, favelas, barrios, or townships—are not aberrations. They are the primary mode of urbanization in the Global South, housing an estimated 1 billion people who build their own shelter on land they do not formally own, connect to water and electricity through self-organized networks, and create economic livelihoods outside regulated markets.

These communities are invisible to official data systems—absent from census counts, cadastral maps, and municipal service plans. Yet they are among the most densely populated, economically productive, and socially resilient urban spaces in the world.

Why It Matters

By 2050, an additional 2 billion people will live in cities, mostly in Africa and South Asia, where formal housing markets cannot remotely keep pace with demand. Informal settlements will absorb much of this growth. How governments respond—with bulldozers or with upgrading; with eviction or with inclusion—will determine the quality of life for billions and shape the trajectory of entire nations.

The Research Landscape

Bulldozer Urbanism in Accra

Okwei and Adjaison (2025), with 3 citations, document state-led evictions of informal settlement residents in Accra, Ghana, using Cernea's Impoverishment Risks and Reconstruction framework. Evictions—justified by "urban modernization" and "beautification"—destroy established communities, livelihoods, and social networks. Relocated residents face worse outcomes on every dimension: longer commutes, lost income, disrupted children's education, and severed social ties. The study demonstrates that demolition without adequate resettlement is not urban planning—it is state-inflicted impoverishment.

Participatory Data for Inclusion

Mangara and Dorasamy (2025) argue that the exclusion of informal settlements from official data systems is itself a form of governance violence. In South Africa, where one in four urban residents lives informally, they develop participatory data collection methodologies where community members co-produce the maps, surveys, and assessments that formal planners use. This approach simultaneously generates accurate data and builds community capacity for engagement with municipal governance.

Community-Led Flood Adaptation

Bhanye (2025), with 16 citations, reviews community-based flood adaptation in informal settlements across the Global South. Informal settlements are disproportionately located in flood-prone areas—riverbanks, coastal lowlands, drainage basins—because these are the only unoccupied land accessible to the poor. Community-led approaches (drainage construction, flood warning systems, elevated building techniques) are often more effective and sustainable than top-down interventions because they build on local knowledge and maintain community ownership.

Global Scale Estimation

Boanada-Fuchs and Samper (2024), with 32 citations, provide the most comprehensive global estimate of informal settlement size and location. Analyzing city-level slum maps across 30 cities, they estimate nearly 1 billion slum residents in 2015, projecting 380 million more by 2030. A key finding: only half of all slums are located within the administrative borders of cities—meaning municipal planning processes systematically miss settlements beyond their jurisdictional boundaries, and shifting urbanization trends mean informality will remain a defining feature of 21st-century cities.

Informal Settlement Governance Approaches

| Benign neglect | Ignore informality | Continued vulnerability | Many cities | | In-situ upgrading | Improve existing settlements | Incremental improvement | Medellín, Mumbai | | Participatory planning | Co-produce with communities | Empowerment + infrastructure | SDI/SPARC networks | | Tenure regularization | Formalize land rights | Security, investment incentive | Peru, Thailand |

What To Watch

Satellite-based mapping combined with AI is enabling automated detection and monitoring of informal settlement growth in near-real-time, providing governments with the data needed for proactive rather than reactive planning. The concept of "hybrid formality"—where settlements maintain informal social organization while accessing formal services through negotiated agreements—is emerging as a pragmatic alternative to the false binary of formal/informal.