Affordable Housing Innovations 06: What is a slum? Twelve definitions

By David A. Smith

March 1, 2013

Slums are among the least well understood places on earth, in large part because they are among the most complex places on earth. At AHI we use as many as twelve definitions of slums, all of them incomplete, all of them true.

1. Not the formal world's mental image

The developed-world conception of slums is of previously formal housing, often built or operated by the government, which has become a vertical rabbit warren of the underclass.


Emerging-world slums are completely different: never formal, usually self-built, organized not by formal society but by informal residents themselves.

Developed world

Emerging world

Originally formal, now grown informal

Originally informal, striving to formalize

Government sponsored and subsidized

Pure private, suspicious of government

Governed top-down

Governed bottom-up

2. Highly dense, low-rise, substandard, and unhealthy

Emerging-world slums pack an enormous number of people into a very small land area. Nairobi's Kibera vies with now-demolished Kowloon Walled City and New York's 1895 Lower East Side for the highest-density habitation ever experienced on earth.

Because they are largely self-constructed with low-cost local building materials, slums are low-rise: initially ground floor, eventually building up to two or three stories at the absolute maximum.

All these poor people crammed into incredible proximity (in Kibera, the average person lives in 10 m², 100 sf) make living conditions substandard and unhealthy. For slum dwellers, hygiene is an enormous challenge – the simple things we take for granted are daily struggles. Gastrointestinal, respiratory, and water-borne diseases are common throughout, touching all ages and genders.

Welcome to the informal and formalizing world

3. A dangerous place to live

Slums are dangerous places to live and work.

Unpaved roads and open sewers invite or cause accidents. Injuries are common and often go untreated, because to be injured is to be unable to earn even a meager living.

Women in slums, often the principal family breadwinners, face dangers every day. Domestic violence is common, especially when the family suffers a financial reverse or medical emergency. If a home lacks a toilet, as many do, women are at risk of robbery or rape when they venture out at night.

Then too, slums can be havens of crime, much of it (drug dealing, prostitution, and gambling) tolerated, even desired, by elements of the formal city.

4. A self-built spontaneous community

Emerging-world slums are self-built. People immigrate to the city in search of a better life – and they are right to do so, because for all its faults, the city offers them better income prospects and education for their children. Upon arrival, immigrants find too little housing to accommodate them, so they build their own, applying their own skills on found or scavenged materials.

They build what they can live in, nothing more. In time, they densify what once was rural or peri-urban. As my friend Michael Mutter says, "You can become urban without moving."

5. Where private investment has outrun public infrastructure

At the beginning, most slums are consciously ignored by the formal city. ("Maybe they'll go away.") The slum dwellers settle on land that is available to them – usually poor quality, sloping, flood-prone, or downwind of the paper mill.

This poor-quality land lacks infrastructure. Roads emerge from the dirt and mud between buildings. Water is bought from vendors and carried home in bottles. Toilets are pit latrines (at best; many slums use 'bush toilets,' defecating in the open) with night soil carried away by wheelbarrow. Electricity comes through jury-rigged wiring that bypasses meters.

6. A wealth-extraction machine

Slums extract wealth from their slum dwellers: it costs money to sleep on the pavements of Delhi or Mumbai. Wealth leaches out in protection, in bakshish to public officials to look the other way, in rent paid to absentee landlords (or their intermediary rent collectors), and in high unit costs for basics like poor-quality water or sanitation. These costs are priced and consumed at people's subsistence level, because it's expensive to be poor.

7. Where physical reality and legal documentation are wildly at odds

Kibera, the largest slum in Africa, is not shown on the map of Nairobi, which instead lists the area as a lake abutting the Nairobi Dam. The formal cadaster never reflects the physical reality of slums. This contributes to a cognitive dissonance: we cannot acknowledge the slum's existence, yet every bit of its existence proves the invalidity of our laws.

8. Alternative-universe power structure

The order that emerges inside a spontaneous and self-built community is purely internalized; the outside law has little meaning, because the law seldom enters the slum.

Power may flow through organized crime, gangs, or tribal, ethnic or language groups. It may cluster around synagogues, churches or mosques; or it may be built from employment guilds or savings cooperatives. Everyone in the slum knows its power structure and treats it with deference – or else.

9. Hives of entrepreneurs

Slums are never silent … because they are never at rest. They have barbershops, bakeries, movie theaters, furniture makers, materials resellers, DVD repairmen, shoemakers, vegetable sellers, and seamstresses. Slums are the empire of informal and home-based workers, and the fastest incubators of business innovation I've ever seen. Slums are where informal jobs in the wider city go to sleep at night.

10. A self-organizing ecosystem

Slums become self-organized and self-repairing ecosystems. They evolve and adapt with extraordinary speed, and because they are comprised of thousands of people who become expert at maximizing output from scant resources, slums are amazingly smart and resilient.

Slums leveled and demolished by a storm or a dictator can be reconstituted in a week.

11. 'Economically rational' delivery of 'affordable housing'

Slums are thus a perfect expression of market forces at work: they are the adaptive response to rapid urbanization, producing economically rational affordable housing – minimum-quality dwellings paid for by the city's poorest people. All of slums' negative externalities – density, lack of hygiene, danger, alternative-power universes – are consequences of the relentless application of pure-market principles to the problem of rapid urbanization.

As I've said for years, "The pure private markets will create all the affordable housing people can pay for. It's called a slum."

12. A phase every rapidly urbanizing city goes through

Every rapidly urbanizing city – including Augustus Caesar's Rome, 1780s London, or 1880s New York – goes through a period of slum proliferation because people are coming to the city much faster than the city's physical infrastructure and democratic governance can keep up. They appear in a rapidly changing city, and their emergence likewise changes that city.

From the slum to the formal city

Future essays of Affordable Housing Innovations will cover how a slum evolves, and what distinguishes a good slum from a bad slum.