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ARQ (Santiago)

versión On-line ISSN 0717-6996

ARQ (Santiago)  no.98 Santiago abr. 2018 


Slums. Disassembling the Concept

Alejandro De Castro Mazarro1 

1Professor, Graduate School of Architecture, Planning and Preservation, Columbia University, New York, USA.


The idea that language constructs realities is almost commonplace. When looking at problematic contexts, however, the urgency to find a solution makes us forget that language also constructed this reality. By analyzing the concept of 'slum,' this text explains that its construction as a massive problem at a global level demanded an ambiguity that allowed it to adapt both to the different realities and to the expansive interests of the global agencies in charge of solving it.

Keywords: development; UN-Habitat; language; poverty; hegemony

The last decade of the 20th century saw the re-emergence of slums in the hegemonic architectural discourse, with its apex at an almost simultaneous celebration of Alejandro Aravena’s Pritzker Prize and his nomination as Director of the Architecture Venice Biennale in 2016. In this period both specialists and starchitects alike (i.e. U-TT or Rainer Hehl, Rem Koolhaas or Herzog & De Meuron) disseminated ideas on slums and precarious urban areas, and promoted ‘humanitarian’ or ‘advocacy’ alternatives within the architectural field. This disciplinary reform, reminiscent of a climate of hope targeting a better urban habitat “for the greatest number”6 of the mid 20th century, was fostered by a global urban agenda targeting slums in the aftermath of the United Nations (UN) Millennium Declaration (2000). In this period, the UN characterized the essence, geography, and history of slums and, by 2003, reported the existence of 1 billion of slum dwellers. The majestic simplicity of this figure, institutionalized by the world’s leading international development agency, made clear what architects and urbanists should fight against. ‘Slums’ had, in this context, the ability to assemble the greatest number - namely the masses of billions of people living in poorly constructed environments - to the call of one only word; so that those masses would raise their living standards if the presence of such word declined worldwide. This text examines how this assemblage was produced - how concepts and evidence were put together - and shows the contradictions that make this assemblage inconsistent. As it will be exposed, the UN’s characterization of slums provides only a slanted portray of the billions of urban dwellers living in scarcity, as well as an implicit support to the Modernization Theory.

The spatial relevance of a social problem

Slums returned to the global urban policy arena in the advent of the Millennium Declaration, a charter that aimed to renew the ambitions of the 1948’s Universal Declaration of Human Rights, while innovating in its capacity to be monitored and evaluated. To this end, the UN subscribed to eight theme-based Millennium Development Goals, or MDGs, each composed of policy targets and indicators for monitoring progress. In the 1990s, UN agencies prepared their fitting to the Millennium Declaration and UN-Habitat, the smallest of its agencies, found in ‘slums’ a synthetic, striking problem that could raise its institutional relevance vis-à-vis the monitoring of MDGs (Gilbert, 2007). The Millennium Declaration cited the UN and the World Bank’s joint urban upgrading initiative “Cities Without Slums”, as a first stroke of the repositioning of slums as part of UN-Habitat agenda. But for the MDGs slums became central to its mission: from its 48 indicators, UN-Habitat only had to monitor number 32: “Proportion of urban population living in slums,” belonging to the policy target 7.10: “to have achieved a significant improvement in the lives of at least 100 million slum dwellers.”7

With its agency centered on the monitoring and evaluation of MDG target 7.10, UN-Habitat and UNDP consequently put institutional efforts to clarify, in the five years following the Millennium Declaration, what were ‘slums.’ Their results appear most prominently in five published books: The Challenge of Slums: 2003 Global Report on Human Settlements (UN-Habitat, 2003a); Slums of the World: The Face of Urban Poverty in the New Millennium? (UN-Habitat, 2003b); Investing in Development: A Practical Plan to Achieve the Millennium Development Goals (UNDP 2005a); A Home in the City: Task Force on Improving the Lives of Slum Dwellers (UNDP 2005b); and, The Millennium Development Goals: Raising the Resources to Tackle World Poverty (Cheru, Fantu and Bradford Jr., Colin, 2005). By 2015 (the “expiration date” for the MDGs) the target 7.10 was achieved: life had improved for more than 100 million slum dwellers - however in that time slums added many more than 100 million new dwellers.

This was not an abstract policy discussion but, in most part, an architectural and urban planning conversation. UN-Habitat is linked to discussions about shelter and housing, urbanism and cities since its inception at the 1976 Vancouver Conference on Human Settlements. CIAM members like Michel Ecochard or Josep Lluís Sert; and renowned architects like John Turner and Jorge Mario Jáuregui have been related at some point with the institution. Its outgoing Director Joan Clos was the mayor of Barcelona at the time the urban planning ‘Barcelona Model’ became an international best-case (1980s-1990s); and UN-Habitat staff is made up mostly of urban planners, designers, and architects. In the context of the MDG’s, UN-Habitat commissioned leading urban research centers to do preliminary work for its agenda: University College of London’s Development Planning Unit, for example, carried out a set of studies of slum conditions, policies and strategies in preparation to The Challenge of Slums, including primary research in about 34 city case studies; and, UN’s Task Force 8 (the Task Force on Improving the Lives of Slum Dwellers), coordinated by architects and planners from Columbia University and the University of Rome, presented policy recommendations to improve slums at the report A Home in the city (UNDP, 2005b). It is thus hard to underscore that the MDGs represented the opportunity to leverage the role of architects and urban planners in having a global social agency, in which spatial skills could service a social assemblage of 1 billion dwellers - and growing.

The construction of an essence

To ultimately achieving the MDGs, the UN goals needed to be operationalized into measurable indicators upon which progress could be assessed. For target 7.10 this required defining ‘slums’ in a way that they could be designated and monitored. This stage paved the way to the arising of an epistemological problem, namely the conflation of realist and nominalist perceptions of ‘slums.’ While the antagonism between realism versus nominalism belongs to the Philosophy of Knowledge, their differences affect the domain of reality to which slums belong to. Concepts like ‘apple’ - realists would argue - have an essence ‘in the real world’; while concepts like ‘justice’ - nominalist would argue - have a socially fabricated essence. Slums, as characterized by the UN, aim to represent the external reality of certain urban settlements, however, they greatly represent the system of values of its creators. This renders itself evident in the definition, geography, and history of slums coined by the UN between 2003 and 2005.

UN-Habitat’s The Challenge of Slums (2003) coined the ‘operational definition’ of slums (Figure 1) that remains, today, the characterization most widely agreed-upon in international urban discussions. The definition came along with a comprehensive survey of more than 300 pages analyzing the forces shaping slums, their social dimensions, their spatial forms and economic dynamics, along with an annex. The definition of slums was, itself, an aggregate of physical and legal indicators applied to urban areas, which naturally fit to propose solutions from architectural and urban planning standpoints: slums “lack of access to water and sanitation” at the definition, would be solved with the provision of physical infrastructure through streets; the “poor structural quality” of their housing would improve with the provision of adequate building standards; and, even the problem of “overcrowding”, could be solved with proper typological housing solutions. The definition, however, presented two biases that undermined its own meaning: one reducing slums to their material cause, and the other simplifying several phenomena into a single term.

Figure 1 Sample of definitions of slums. 

UN’s operational definition of ‘slum’ was “restricted to the physical and legal characteristics of the settlement, excluding its more difficult social dimensions.” The externalization of ‘social’ problems as not belonging to slums ethos assumes that once material problems are solved, social solutions follow. This, at the very least, overlooks the rich history of assessments of slums, in which their spatial and social problems have an ambivalent relationship.

Even the roots of the word ‘slum’ have this ambivalence. The early usage of the term ‘slum’ in the Anglo-Saxon world refers to the physical denomination of ‘back rooms’ in overcrowded, unsanitary habitations in newly industrial British cities; however, urbanists like Bernardo Secchi8 have tied its etymology to the German word schlummer (‘slumber,’ in English), in reference to the “voluntary poor” that were criminalized since the Poor Laws of 1602 in the UK. These two interpretations of slum (one material, the other behavioral) have disputed their primacy in urban planning discussions since the 19th century and can be illustrated in the comparison of early analyses like Friedrich Engels’ “The housing question” (1873) and Jacob Riis’ “How the other half lives” (1890). In this discussion, Engels argued that slums were not a housing problem but a problem of economic inequality; and, in contrast, Riis believed that the cause of slums were the intolerable population densities of industrial working areas - therefore advocating for the construction of newly created suburbs connected by trains.

One could argue that social issues are not part of the UN’s operational definition because of a choice of ‘genre’: the UN’S definition may be anatomic (by revealing its features) and not genetic (by outlining the causes for its formation). However, in the context of the MDGs problems, their causes and solutions are conceived as part of a logical framework - a baseline for the construction of scientific argumentation - and the identification of slums as a material problem does not address their causes, therefore it does not logically prevent their formation. Without thoroughly addressing slums’ root causes, The Challenge of Slums reinforces the binary of concepts ‘poverty vs provision,’ where physical planning and design solve underdevelopment. This leaves out important discussions about social and economic inequality, which have taken place since the inception of slums.

The second bias operating at UN’s characterization of slums is the conflation of multiple meanings within the word ‘slum’ itself; this happens both synchronically and diachronically. Synchronically, UN-Habitat (2003a) provided a list of “equivalent words in other languages and geographical regions” (Figure 2, black text) that was not comprehensive - as a search on other words that are popularly associated with slums reveals (Figure 2, magenta text). UN-Habitat itself (2003:10) warned against the possible oversimplification of different meanings; however, the list allowed for the free association of concepts that could fall under the umbrella of ‘slums,’ thus simplifying a vast array of urban phenomena to one ‘main’ essence. In practice, these terms are commonly used as quasi-synonyms; this can be illustrated, for example, in the way Jorge Mario Jáuregui’s Favela-Bairro projects appear in publications: while Lotus (2010) titles an article on this Rio de Janeiro program as “Slum to Neighborhood” and mentions that “about a quarter of Rio’s population (…) lives in favelas” (2010:61), Jáuregui himself describes favelas as communities (Architectural Design, 2011:60); and, Architecture for Humanity’s Design Like You Give a Damn (2006:216) describes Rio’s favelas as “unplanned shantytowns housing one-third of the city’s population.” All these terms have, of course, a related meaning to the favelas where Jáuregui has worked, but an all-inclusive use of words empties ‘favelas’ of part of their substantive meaning.

Figure 2 Slums’ equivalent terms, per region and country. Based on UN-Habitat (2003a) and own elaboration. 

Diachronically, architects and planners do not differentiate between post-MDGs ‘operational’ slums and pre-MDGs slums themselves, however, their meanings are quite different (Figure 1).

The indicators described at the UN’s definition of slums could have been composited as an acronym; the use of the word ‘slum’ to that composite adds a linkage to the Anglo-Saxon history of Western industrialization and implicitly reveals a preference for a center-periphery narrative. Even in the 19th century, when slums were prevalent in the UK, urban problems related to industrialization and development were beyond Thomas Annan and Jacob Riis’ ‘slums.’ Eugène Atget’s depicted zoniers and chiffoniers in Paris; Harry Olds portrayed conventillos in Buenos Aires and barracões in Brazil; Augusto Malta represented favelas in Rio de Janeiro; and Hölzstich’s painted Germans’ elendsquartier. In brief, the reification of slums above other historical and geographic precedents aimed to gather the greatest assemblage possible - precarious urban dwellers worldwide and in history - but the assemblage dissipates as the concept loosens its meaning.

Slums in place and history

While UN-Habitat’s The Challenge of Slums (2003a) reified the status of slums as an urban problem, the report Slums of the World (UN-Habitat 2003b) presented a preliminary methodology for estimating the total number of slum dwellers worldwide, based on its operational definition. But it was only in 2005 when the global share of urban residents living in slums appeared, at UNDP’s book titled Investing in Development. (Figure 3)

Source: United Nations Development Programme (2005b:27)

Figure 3 Share of urban population living in slums (percent). 

The power of this global picture resides in its capacity to resolve complexity - the weighting of variables, and the normalization of data across countries - into an elegant synthesis that reinforced a world divided by developed versus developing countries, and that was in line with the association of slums to material poverty. The thorough analysis of this map exceeds the purpose of this text; however, a small mention can be made to highlight its confirmation bias. In the picture, sub-Saharan Africa and South Asia have the highest range of slum prevalence, while “High-income countries” remain outside of a measurable range - as if, by definition, slums cannot exist in the context of ‘high economy.’

The ultimate naturalization of slums occurs at the creation of their own history, something that the UN presented as a timeline representing the growth of urban and rural populations worldwide since 1800. A meter-wide reproduction of this timeline decorated, until recently, the office of the UN-Habitat Director in New York (Figura 4); and within published media, the timeline appears at a book chapter co-authored by the former Director of UN-Habitat Anna Tibaijuka (Tipping, Adom, and Tibaijuka 2005). Its authorship is, however, unclear: since the timeline offers no references, it may be attributed to Tibaijuka herself, or to the Swedish architect Lars Reuterswärd, who authored a very similar figure in the book, and who was Director of Global Division of UN-Habitat at the time of the publication. The graph shows that since 1900, when slums became statistically significant, the growth of slum population has been approximately proportional to the growth of total urban population.

Figure 4 Illustration decorating the office of UN-Habitat’s Director in New York. The illustration corresponds with the figure 10.1 appearing at Cheru and Bradford (2005). At the book, the image source is Lars Reutersward  

All evidence in this timeline points to the construction of a visual narrative of developmentalism, and not of slums’ history. In it, post- and pre-MDG definitions of slums blend into a continuous line representing slum dwellers in the period 1800-1950, an elegant simplification that yet would require vast amounts of data about slum conditions in the past; about their conditions before the term ‘slum’ was actually coined; about the ‘conversion rate’ existing between English-speaking and non-English-speaking slums in 19th century; and, about the normalization of information gaps. For a graph of such ambition, it neither mentions sources, nor they are indirectly available at some other work from its potential authors: none of them are historians, and Reuterswärd himself has a small academic publication record.9 An in-depth search for sources of this chart rendered no findings; and in their absence, the timeline is something one has to believe - or, in technical jargon, it is not falsifiable.

The timeline shows the exponential growth of slums particularly since the 1950s - 19th century slums ‘epidemic’ in Europe and the U.S. seems not to be relevant quantitatively - and aligns with the historical narrative of the Modernization Theory: population growth in developing countries has not been matched by proper industrialization and institutional control, thus the quality of life of their urban dwellers has been severely disrupted. The chart does not consider that slums, understood after the operational UN definition, may have been the prevalent mode of urbanization throughout most of human history. Historians agree, in fact, that most of the inhabitants of ancient Rome lived in appalling slums (Scobie, 1986). Urban deprivation may have existed since the dawn of urbanization, and therefore UN-Habitat’s call would need to look into the structural characterization of the problem, and not only to its contemporary physiology as if it were a historical novelty.

The support of the chart to a developmentalist imaginary appears, at last, in the solutions it offers to the exponential growth of slums. These solutions - a combination of urban development, slum upgrading and regional development policies targeted to different population sectors - have largely been applied since many decades ago, and did not eliminate slums. Thus, the chart implicitly suggests that eliminating the increasing size of slums does not require a ‘revolutionary’ approach, but rather an exponential increase in scale, of already tested pro-development policies.

Harnessing ‘bad’ as a category for urban spaces

The UN’s definition, characterization, and history of slums had the laudable goal to operationalize a set of complex urban problems in view of their solution, yet it had a limited capacity to invoke its essence and address its dwellers. The concept behind that essence was, at least partially, inconsistent: slums were reduced to a material substratum, and its concept and history had a confusing demarcation vis-à-vis other past and foreign concepts. At the same time, slums, as defined for the MDGs, carried an essence out of their own that belongs to the development of the Modernization Theory. In this logic, slums are a by-product of an imperfect modernization that can transition to modern and emancipated societies by bringing efficient systems like tenure systems, building reform, and physical infrastructure. This agenda, broadly characterized, however relevant on its own, turns problematic when it does not differentiate - itself - from slums - themselves. And, this division is of great importance, because it maintains the delicate balance involved in the use of power and the possession of knowledge.

The MDGs’ attempt to unify in ‘slums’ the billions living in bad urban conditions resulted in a mirage that partially represented those areas, and partially represented an international development discourse. ‘Slums’ remains an expression of disapproval or oddness, whose ultimate meaning is still insurmountable and ambivalent. The incapacity to create a consistent definition of ‘slums’ may be pointing to a deeper ontological weakness, namely the weakness of the category of ‘urban space’ to unify the overly complex relationship existing between the social and spatial dimensions of cities. The grand narrative surrounding the institutionalization of slums as part of the MDGs claimed knowledge and control over urban spaces; however, too many issues - overcrowding, inequality, urban violence and lack of physical infrastructure - cannot be encapsulated into a single concept. The solution to this epistemic dilemma may lie close to reality, where problems receive clear, perhaps more humble names.


I would like to express my gratitude to Eder García, Jack Darcey and Rafael Kalinoski, research assistants at Columbia University during the summer of 2015 and 2016, and who provided background information relevant to this paper.


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* Alejandro de Castro Mazarro Architect, MSc. in Advanced Architectural Design, Columbia University, 2009. Doctor in Architecture, Universidad Alcalá de Henares, Madrid, 2016. Contributed to the Chilean Architecture Biennial (2017), and the exhibition Participatory City at the Guggenheim Museum at New York (2013). He is co-editor of the book Who cares for Chilean cities? (ARQ and GSAPP, 2014) together with Francisco Díaz. De Castro Mazarro is Professor at Columbia University, and has been visiting professor at Harvard University, TU Darmstadt (Germany) and the International University of Catalonia in Barcelona.

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