Housing Poverty and Homelessness
Roughly 1.1 billion people — about 24% of the world's urban population — live in slums or informal settlements without secure tenure, basic services, or adequate housing. An additional 100+ million people are homeless globally by various estimates. The two phenomena differ structurally: informal settlements are concentrated in fast-growing cities in low- and middle-income countries; visible street homelessness is concentrated in advanced economies.
Key insights
Informal settlements are the urbanization underside
Sub-Saharan African cities have informal-settlement shares often 60-80% (Lagos, Kinshasa, Nairobi, Dar es Salaam). South Asian cities run 25-50% (Mumbai's Dharavi famously). Latin American shares 20-30% (Rio favelas, Mexico City colonias). These settlements typically have no formal land tenure, partial utility access (often illegal), and exclusion from many services. Upgrading rather than clearance is the modern policy consensus.
Homelessness in advanced economies has multiple causes
US homelessness reached 770,000 (2024) — the highest count since records began. The UK, France, Germany all show recent increases. Drivers: housing-cost rises outpacing wages, mental health and addiction crises, exit barriers from prison/foster care, immigration shocks. Finland's Housing First approach (1987-onward) is the most-studied alternative — providing immediate housing without preconditions has produced sustained declines in chronic homelessness.
Data is exceptionally weak globally
Slums and informal settlements are by their nature under-enumerated. National censuses often skip them; satellite-based estimation (UN-Habitat) fills some gaps but with wide uncertainty. Homeless counts vary by methodology — point-in-time counts capture less than annual counts. Cross-country comparisons of either are unreliable beyond order-of-magnitude. The data inadequacy is itself a policy problem.
Slum share of urban population — selected regions
% of urban population living in slums (UN-Habitat 2020)
Key Finding: Sub-Saharan Africa has the highest slum population shares; the share is declining slowly in most regions.
Homelessness rate — selected developed countries
Per 10,000 population, comparable methodologies
Key Finding: US has notably high homeless rates relative to peer economies. Finland has fallen substantially under Housing First.
Methodology & caveats
Defining 'slum'
UN-Habitat slum definition: households lacking one or more of: durable housing, sufficient living area, access to improved water, access to improved sanitation, secure tenure. Different countries use different thresholds; comparisons should treat the headline figures as broad orders of magnitude rather than precise.
Counting homelessness
Methods range from: point-in-time street counts (US HUD), service-user counts (UK), administrative records (Germany), housing-need registries (Sweden, Netherlands), one-night census (some Nordic countries). Counts often miss: hidden homelessness (sofa surfing, doubling up), street-avoiding individuals, those in vehicles. True counts are 1.5-3× headline figures by most methodologies.
Housing First evidence
Finland adopted Housing First nationally from 2007. Long-term homelessness fell ~70%. Mechanisms: providing housing first (rather than as a reward for sobriety/treatment) reduces psychological barriers and lets people stabilize. The model has been adapted in Canada, France, parts of US. The evidence base is now strong; political and capital-cost barriers remain the implementation constraints.