It is estimated that at least 1 billion people globally live in informal settlements or slums — unplanned areas that fall outside of legal and regulatory systems — and the actual number is likely much higher.
These communities lack access to adequate basic services and infrastructure like good quality housing, water, sanitation, energy or transportation, and are often located in parts of the city that are under-served and highly vulnerable to environmental and climate risks.
Local governments often overlook the deprivations faced by residents of informal settlements, who are typically from the lowest socioeconomic classes, lack legal property rights and remain uncounted in formal surveys and censuses. These settlements are unplanned areas that fall outside legal and regulatory systems and highlight the immense inequalities in access to services and infrastructure in cities.
Rapid urbanization, ineffective planning, lack of affordable housing and lack of effective housing policy are some of the reasons cited for slum formation in developing countries. If this type of growth continues, cities in developing countries could see the rise of mega-slums that are vastly under-served. Research shows that a 1% increase in urban population growth will increase the incidence of slums in Africa and Asia by 2.3% and 5.3%, respectively.
In 2020, 24.2% of the urban population globally lived in slums or informal settlements. Sustainable Development Goal (SDG) 11.1.1 aims to ensure access for all to adequate, safe and affordable housing and basic services and upgrade slums by 2030, thereby setting a target for this indicator of 0% by 2030. While this number has been trending downward, from 31.2% in 2000, the world would need to accelerate progress to decrease the incidence of slums by more than 10 times the current pace to reach 0% by 2030. However, 2 billion more people are expected to live in slums in the next 30 years.