What Causes Urban Slums? Key Drivers of Slum Growth in Cities

Walk through almost any large Indian city and you will find two worlds sitting side by side. Glass towers and gated colonies rise next to dense clusters of tin roofs, narrow lanes, and shared taps. These clusters are slums, and they are home to a significant share of the urban population. The 2011 Census recorded roughly 65.5 million people living in slum settlements across the country. Slums are not random accidents. They are the predictable outcome of how cities grow, how rural areas are neglected, how the economy absorbs labour, and how politics treats the poor. This post breaks down the four forces that drive slum growth so you can see the system behind the settlements.

Rapid urbanization and the housing gap 🔗

The single biggest engine of slum growth is the speed at which cities expand. People arrive faster than housing, water lines, sewers, and roads can be built. When a city cannot supply enough legal, affordable homes, low-income arrivals settle wherever land is available. They build on railway margins, riverbanks, drainage edges, and industrial peripheries. Over time these scattered shelters harden into permanent communities.

India is urbanizing quickly. Around 31% of the population lived in urban areas at the time of the 2011 Census, and that share keeps rising. Each new wave of urban residents increases the demand for land and pushes formal housing prices higher. Research on urbanization patterns shows a strong link between the pace of urbanization and the growth of slum populations, especially where city governments fail to plan for the incoming population.

The affordable housing shortfall 🔗

The core problem is not migration by itself. It is the mismatch between what migrants can pay and what the formal market offers. Real estate prices and rents in major cities are far beyond the reach of daily-wage earners and entry-level workers. The private sector has little incentive to build cheap rental housing, and public housing has historically fallen short of demand. The Pradhan Mantri Awas Yojana set a target of building crores of homes, yet the gap between need and supply remains wide.

When affordable formal housing does not exist, slums become the only option. They function as the city’s informal housing market. They offer cheap rooms close to work, which is exactly what a low-income worker needs. This is the key insight: slums grow not because people prefer them, but because cities leave no legal alternative within the budget of the working poor. Rigid and outdated planning rules make this worse by criminalizing the only kind of housing the poor can afford.

Slow rural development as a push factor 🔗

Cities pull people in, but villages also push people out. When rural areas offer too few opportunities, families have little choice but to leave. Agriculture supports a large share of the rural population, yet it provides shrinking and seasonal incomes. Small landholdings, low farm prices, debt, and a lack of non-farm jobs leave rural households trapped. Environmental stress adds to the pressure. Floods, droughts, and soil erosion make farming unreliable and force people to look elsewhere for survival.

This regional imbalance in development shows up clearly in migration patterns. States with weak rural economies send large numbers of workers to richer cities. A post-pandemic survey of low-income workers in Delhi and Mumbai found that around three-fourths of inter-state migrants came from Bihar and Uttar Pradesh. These are states where rural development has lagged behind, and where the absence of local jobs becomes a one-way ticket to the slums of metropolitan India.

It is important to see that rural and urban distress are connected. A worker leaves a village because rural development failed, then lands in a city that has no affordable housing for them. The slum is where these two failures meet. Fixing slum growth therefore requires investment in villages and small towns, not only in big cities. If rural areas offered stable incomes, the pressure on urban land would ease considerably.

The pull of informal sector employment 🔗

The economy of Indian cities runs on informal labour, and this is a powerful reason slums keep expanding. Over 90% of India’s workforce is employed informally, without contracts, fixed wages, or social security. The urban informal sector plays a crucial role in providing livelihoods to migrant workers and low-income households in slums. Construction sites, domestic work, street vending, waste picking, and transport all depend on this floating pool of cheap labour.

These jobs draw workers into the city, but they pay too little to afford formal housing. A construction labourer or a domestic worker earning a daily wage cannot rent a flat at market rates. Reports on internal migration note that informal-sector migrants face wages too low to meet both housing and health costs, which is exactly why so many of them end up in slums. The slum is not a side effect of informal work. It is the housing system that informal wages can support.

Why informal work and slums reinforce each other 🔗

Informal employment and slum living feed one another in a loop that is hard to break. Workers without formal addresses or documents cannot easily register for public utilities, bank accounts, or subsidized housing schemes. Without these, they remain locked out of the formal city. Their work is essential, yet they receive almost none of the protections that their labour supports. Studies of migrant labour in construction, hotels, and manufacturing describe a workforce marked by low wages, insecure conditions, and a near-total absence of social protection.

There is a deeper economic point here. Cheap, easily replaceable labour keeps city economies competitive and keeps costs low for employers. Dharavi in Mumbai, one of Asia’s largest slums, generates large economic output while employing a huge share of its own residents. The city benefits from this labour but does not invest in housing it properly. As long as the economy demands cheap informal labour and refuses to house it formally, slums will keep growing alongside the jobs.

Political dynamics and the persistence of slums 🔗

The first three factors explain why slums form. Politics explains why they persist and expand instead of being cleared or formalized. Slums are large concentrations of voters living in one place, which makes them valuable to political parties. Promises of water connections, electricity, ration cards, and protection from eviction become bargaining chips during elections. This is the well-known pattern of vote-bank politics, where the urban poor are courted with short-term benefits rather than lasting solutions.

Academic research has shown that the state is not simply a passive bystander to slum growth. A study of informal housing governance in Mumbai argues that, because slums serve social, economic, and political functions, it is often in the interest of state actors to allow slums to grow. Politicians and officials may permit new settlements, legalize existing ones, and supply services and patronage to slum residents. These actions stabilize slums and tie residents to political networks, which keeps the settlements in place election after election.

Patronage, regularization, and incomplete tenure 🔗

This relationship is more complex than simple manipulation. Slum settlements often develop their own leaders, who are usually first-generation migrants working in the informal sector. Research from the Center for the Advanced Study of India describes how these leaders help residents access ration cards, voter IDs, electricity connections, and pensions, and organize their communities to demand roads, drains, and protection from eviction. Parties cannot simply install loyalists. They have to work with leaders who already have genuine influence inside the settlement.

The result is a partial, unstable arrangement. Slum dwellers gain informal protection and some services, but rarely secure legal land titles. Without tenure security, residents hesitate to invest in better housing because they fear demolition. Politicians benefit from keeping the relationship informal, since secure titles would remove the leverage that patronage provides. So the slum survives in a grey zone, neither cleared nor formalized. This political incentive structure is a major reason slums endure for decades, expanding rather than disappearing as cities grow richer.

How the four factors work together 🔗

None of these forces operates alone. Rapid urbanization creates demand for housing that the formal market cannot meet. Slow rural development pushes a steady stream of people toward cities. The informal economy pulls them in with work that pays too little for legal housing. Political dynamics then lock the resulting settlements in place by trading services for votes while withholding secure tenure. A slum is the meeting point of all four failures at once.

Understanding this system matters because it changes what a solution looks like. Clearing slums or evicting residents treats only the symptom. A lasting response has to attack each driver: building genuinely affordable housing, investing in rural economies and small towns, extending labour protections and social security to informal workers, and granting secure land tenure so residents can improve their own homes. Slum growth is a structural problem, and structural problems need structural answers.

What do you think? If informal workers are essential to keeping cities running, who should bear the responsibility for housing them with dignity? And in your own city or region, which of these four factors do you think plays the biggest role in driving slum growth?

References

1. https://hrdc.gujaratuniversity.ac.in/Uploads/EJournalDetail/30/1046/80.pdf
2. https://blogs.worldbank.org/en/peoplemove/inter-state-migrant-workers-india-policy-decent-world-work
3. https://www.tandfonline.com/doi/full/10.1080/00220388.2021.1898593
4. https://indiaemployerforum.org/human-capital/internal-labour-migration-in-india/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC7680072/
6. https://www.sciencedirect.com/science/article/abs/pii/S0264837717301680
7. https://casi.sas.upenn.edu/iit/auerbachthachil1