Why did favelas expand in Rio de Janeiro during the 20th century?

The expansion of favelas in Rio de Janeiro during the 20th century was primarily driven by rapid urbanization and significant rural-to-urban migration, particularly between the 1940s and 1970s.1

Several key factors contributed to this growth:

• Migration and Housing Shortages: As Brazil shifted from a rural to an urban society, the supply of affordable, formally regulated housing failed to keep pace with the influx of migrants. This forced many low-income residents to establish informal settlements on the urban periphery or on steep, otherwise undesirable hillsides.12
• Economic Pressures: Rising urban land values and real estate speculation in the latter part of the 20th century further marginalized the poor. As rents increased, many residents were displaced from the central city and compelled to move to expanding favelas.34
• Lack of State Oversight: Favelas developed as informal settlements without public authority oversight. Because the state did not provide adequate housing or infrastructure, residents relied on self-built housing and incremental construction, often creating their own systems for essential services like water and electricity.15