India’s urban transformation has been accompanied by an enduring puzzle: how many people in its cities actually live in slums? The official answer, offered by Census 2011, was about 65 million. Yet, researchers and international agencies such as UN-Habitat, the World Bank and the Asian Development Bank have consistently arrived at much higher numbers, sometimes approaching 90 to 100 million.
This gap is not a minor statistical discrepancy. It reflects deeper flaws in how slums are defined and measured, and it has direct implications for policy, service delivery and, ultimately, the well-being of millions of urban residents.
The Census currently recognises three types of slums: notified slums formally declared under law, recognised slums acknowledged by local authorities, and identified slums comprising at least 60 to 70 households in poorly built housing lacking basic services.
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The problem with India’s slum data
While this framework has provided some baseline, it suffers from two fundamental limitations. The first is the size threshold. Smaller clusters of hutments or dispersed informal settlements are excluded if they fall below the household benchmark. These may display every feature of deprivation, lack of sanitation, insecure tenure, overcrowding—but they are invisible in official counts because they do not meet the minimum size criteria.
The second limitation is that the census emphasises the legal or administrative status of a neighbourhood rather than the condition of the housing itself. This produces distortions in both directions. Well-built houses located in areas historically designated as slums are counted as slum households, while poorly constructed shacks in non-designated neighbourhoods are not. In practice, this means the Census both undercounts some of the most precarious households and overcounts others that are not deprived.
Scholars have highlighted these problems, showing how census definitions systematically miss many informal settlements while, in some cases, overstating poverty in others.
A more practical way of measuring slums is to focus directly on household type. This method classifies households based on the physical structure and dwelling quality rather than the designation of the neighbourhood. After extensive piloting and training, surveyors can consistently place households into five categories.
A new approach to measure urban deprivation
The two most important categories for measuring slums are Household Type 1 (informal shack settlements) and Household Type 2 (informal slum settlements), which capture the most precarious and deprived forms of housing.
The first type are typically self-built structures made from tarpaulin, tin sheets, sackcloth, or reclaimed wood, often located in vacant lots, roadside spaces, under flyovers, or on medians and green strips, sometimes even inside unfinished or abandoned buildings. They can be single- or two-storied, but their construction materials and locations mark them as deeply insecure.
The second type are slightly more permanent but still precarious: one-room row houses with corrugated metal roofs, tightly packed in dense clusters, often hidden in gullies or lanes behind more formal buildings, with small or shuttered windows, limited ventilation and minimal amenities. These settlements are frequently interspersed with Type 1 dwellings and small commercial shops, creating mixed neighbourhoods of precarious housing.
The framework also recognises Household Types 3, 4, and 5, which represent progressively more stable housing: from lower middle-class concrete homes and relocation apartments (Type 3) to larger middle-class dwellings (Type 4), and finally to upper-class houses and gated complexes with amenities (Type 5). These categories provide a fuller picture of the urban housing spectrum, but for identifying slum-like conditions it is Types 1 and 2 that matter most.
This approach has already been applied in large-scale research. A recent study on citizenship, inequality and urban governance presented findings from 14 Indian cities. It applied the household type methodology for the first time to capture slums systematically. The results were striking.
In Mumbai, for instance, the study found that 62.6 percent of the population lived in slum-like conditions, far higher than the 42 percent reported by Census 2011. This illustrates how official methods, tied to recognition and thresholds, substantially understate the scale of urban deprivation. By contrast, the household type approach provides a clearer and more accurate view of how people actually live in India’s largest city.
The approach focuses directly on material conditions, which are visible and measurable, rather than on administrative recognition. Because it is not self-reported, it avoids the biases that often accompany income or asset questions. Most importantly, it ensures that shack and slum households are systematically included, no matter where they are located on the urban fabric.
By designating Types 1 and 2 as informal, the method underscores the precariousness of these households and their heightened vulnerability. Unlike the Census, which filters deprivation through bureaucratic categories, the new approach identifies the material quality of dwellings and the conditions of everyday life.
Why accurate slum measurement matters for policy
Improving how slums are measured has direct benefits for policy. More accurate numbers allow for more precise allocation of resources for housing, sanitation, and welfare. Differentiating between shack settlements and informal slums enables interventions to be tailored more effectively. Shack households, which are often temporary and highly precarious, may require relocation or rental support, while more established slum neighbourhoods may benefit from in-situ upgrading of infrastructure.
Using a measure that aligns with global frameworks, such as the UN-Habitat’s definition of slum households, also enables India to track progress more effectively toward Sustainable Development Goal 11.
Accurate measurement strengthens monitoring and evaluation. Programmes can be assessed against real baselines rather than under-reported or inflated figures, improving accountability and efficiency. In the longer term, adopting a more reliable measurement system ensures that policies are built on a sound understanding of urban realities.
There are challenges to adopting Household Type classifications. Surveyors need careful training to reduce subjectivity and account for regional differences in construction materials. Institutional adoption may be gradual, since policymakers are accustomed to census-based categories. Yet these challenges are manageable.
Pilot projects have demonstrated strong consistency across surveyors, and clear descriptions and visual guides can further minimise variation. Household Type does not need to replace census definitions immediately; it can be piloted alongside existing systems and scaled up as its advantages become evident.
Measuring slums is ultimately about recognising the diversity of urban living conditions. India’s current approach conceals more than it reveals. A household type–based approach reverses this logic by starting with the observable quality of housing. Focusing on Types 1 and 2 ensures that deprivation is counted where it exists, rather than where it is administratively convenient to recognise it. At the same time, including Types 3 to 5 in the framework acknowledges the broader housing spectrum, situating slums within the larger story of urban inequality.
The recent CIUG project has demonstrated that applying this methodology reveals a far more accurate picture of urban deprivation across Indian cities. The Mumbai example shows how much official figures underestimate the problem. Urban planners and municipal officials must begin with an honest picture of who lives where and under what conditions, to plan effectively on housing, health, sanitation and infrastructure.
The new method can ensure that its poorest urban residents are neither ignored nor misclassified. Accurate definitions cannot solve deprivation, but they can prevent it from being misunderstood. For India’s slums, this would be progress worth making.
Tarun Arora is Associate Professor, Jindal School of Government and Public Policy, O.P. Jindal Global University, Sonipat, Haryana. Reetika Syal is Assistant Professor, Department of International Studies, Political Science, and History, Christ University, Bengaluru. Originally published under Creative Commons by 360info
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