Abstract
Introduction: Urbanisation and the Rise of Slums
The trend of urbanisation and urban growth has taken different forms throughout the world. Cities around the globe have been experiencing ever-increasing levels of urbanisation, and subsequent housing shortages and other socio-economic issues led to large-scale slum development. The average world urbanisation rate has been projected to be 60% by 2030, and about 90% of this future urban growth will be taking place in Asia, Africa and Latin America (United Nations, 2019). The percentage of the slum population is higher in South Asia (30%) than in East Asia and the Pacific (26%), with Africa at 22% and Latin America and the Caribbean showing 20% (World Bank, 2014). The ‘urbanisation of poverty’ has become very apparent in South Asian countries, including Pakistan, India and Bangladesh. Although India and Bangladesh have a similar urbanisation rate, the percentage of the population living in slums in India is 24%, compared to 55% in Bangladesh. Within South Asia, Bangladesh has the second-highest percentage of slum population (55%), surpassed only by Bhutan, where 70% of its total population of under a million are living in slums.
The term ‘slum’ is commonly used to refer to informal settlements found in urban areas that suffer from insufficient housing, overcrowding, and a lack of essential services. UN-Habitat (2007, p. 1) describes a slum as ‘a heavily populated urban area characterised by substandard housing and squalor’. The UN expert group has characterised slums as residential areas having inadequate access to safe water, inadequate access to sanitation and other infrastructure, poor structural quality of housing, overcrowding and insecure residential status (UN-Habitat, 2003). To avoid the derogatory notion attached to the slums, scholars often use the term informal settlement. It also includes illegal structures or settlements in the city (Jones, 2017). The informal settlement also poses the characteristics of the slum (tenure insecurity, lack of services etc). Informal settlements also consider the legality of tenure, where the inhabitants have insecurity of tenure over the land, or the dwelling is considered as an informal settlement. Moreover, any form of real estate speculation, be it for the affluent or poor or people of any income level can be regarded as informal settlement (UN-Habitat, 2016).
Development Interventions in Slums
As urbanisation continues to grow, the issue of housing and the recognition of slums in the Global South began. In 1976, the Vancouver conference predicted the unacceptable living conditions due to inequitable economic growth and uncontrolled urbanisation (United Nations, 1976). However, the issues of slums have received increased attention since the 1990s (Panday, 2020; Humphrey & Shahadat, 2018). Though slum improvement through the site and services schemes started in the 1960s, the horizon of interventions have been widened through the declaration of Millennium Development Goals (MDGs) (Pandey, 2020). Since the inception of MDGs, a considerable amount of policy interventions has been done on slum issues, including providing affordable housing, slum upgradation, provision of basic services, children and women’s health and institutional inclusion (Khan & Swapan, 2013; Patel et al., 2009; Roy, 2005, 2011; Swapan, 2016). Initiatives to improve the conditions of slums have received endorsement from the highest political levels, from national governments to international donor agencies, such as the United Nations (UN) and World Health Organization (WHO). To take the successes of the MDGs forward, the United Nations adopted the Sustainable Development Goals (SDGs) programme in 2016, the aim of which is to take ahead the achievement of MDGs while ensuring a better and more sustainable future by 2030. The goal 11 of the SDG programme aims to make cities ‘inclusive, safe, resilient and sustainable’ by providing affordable housing, basic services and slum upgradation. Like the MDGs, SDGs has specific objective related to slums, which may help slums continue to receive much attention from academics and policymakers.
Increased Academic Attention on Slums
Gilbert (2007) has argued that a plethora of national and international interventions from the 1990s, including the MDGs, have instigated a greater volume of scientific works on slums. Academic research on slums has focused on poverty and inequality by predominantly intervening within a specific geographical boundary and concerns over the issues such as housing affordability and tenure security. As the United Nations (2002) suggests that a typical slum has acute tenure insecurity, with two other issues in common: inadequate space and lack of basic services. To ease the service provisions, a significant number of academic research works went for delineating slum areas within a city (Dewan & Yamaguchi, 2009; Kohli et al., 2013). Traditional as well as GIS and remote sensing technologies are being used to delineate slums for efficient service delivery. The practice of informal governance and informal service providers vis-à-vis landlords and local leaders define the border of the slums (Rana, 2016). This is happening to organise, govern and plan social spaces as well as social life (Passi, 2022). The authors in this paper thus terms slum as a bounded geography.
Missing Places: The Mushrooming of Non-slum Poor Settlements
Tenure security and other slum improvement aspects have predominantly focused on more prominent and recognised slums around the Global South, whereas Gilbert (2007) confirms that such geographical confinement of the initiatives is not adequate. Gilbert (2007) maintains:
Many low-income settlements in the world are anything but homogenous. While some settlements lack every kind of service and infrastructure, many others are partially serviced. Those settlements without water may be classified as slums, but what about those settlements with provision but where some, even many, of the inhabitants cannot afford to pay for it? (p. 700)
Chatterjee (2019) has observed in Mumbai that low-income settlements are growing outside or adjacent to the slums. NGO presence is very unlikely in those areas. Rather, self-help groups are mushrooming. The Centre for Urban Studies (CUS) (2011) reports that in Khulna, the third-largest city in Bangladesh, around two-thirds of the poor households are now living in non-slum areas. Moreover, Khan and Swapan (2013) and Swapan (2016) argue that despite interventions, availability and accessibility of public services in Bangladeshi cities are widening, and special types of relationship exist in slum areas to ensure the services such as water and electricity. With the increasing poor population in the non-slum areas, this growing problem has yet to be addressed in the literature.
With the growing population in cities, tenure insecurity can be found in other parts as well. According to De Soto (2000), legal-status-based property rights (de jure) are considered the true sense of tenure security. Land tenure policies in urban areas are frequently complex and do not simply fall into the categories of formal and informal, or legal and illegal, particularly in the context of developing countries (Payne & Majale, 2004; Varley, 2013). Rather tenure security as the factual situation on the ground determined de facto security (Luciano & Van Gelder, 2015). As Luciano and Van Gelder (2015) state, De facto securities depend on the size of the settlements, lengths of stay, community structures, political acceptance and third party assistance.
Slums in the South Asian cities become more stable, big and politically conscious about their rights. Intervention from donor agencies also increases the political acceptance and reduces the risks of evictions. Residences are enjoying de facto tenure security as they are living for generations. Both the formal and informal transfer of rights (land, house and other properties) are also become common (Rana, 2016). Large-scale eviction has decreased with the help of donor agencies and NGOs (Pandey, 2020). Since the 1980s, local and central governments have increasingly practised the concept of in situ slum upgrading, which is based on the notion that it is socially and economically more effective to allow residents to remain in their communities (Jaitman, 2015).
However, the focus on tenure security has helped little as the cities are experiencing social fragmentation and inequality. Social fragmentation is frequently observed in terms of housing (slum/informal settlements), urban services (limited access to water and sanitation) or resource consumption (household spending on luxury items). The issues of inequality of service accessibility also transcend beyond a specific geographical boundary-the slums or informal settlements. Cities cannot be identified as binary of formal or informal, as the boundary between formal and informal is disappearing with the growing number of settlements. Formal settlements are also converting to informal because formal settlements are also experiencing uncontrolled and sometimes illegal settlements (Dovey et al., 2020). Moreover, despite decades of interventions, it is hard to say that slum residence become the part of the city’s wider decision making process. Dual governance system exists and resource allocation remains inequal (Adnan et al., 2018; Rana, 2016; Swapan, 2016). Mainstream resource allocation becomes segregated from the resources that are supposed to be allocated to the urban poor. Development finance from the international donor agencies primarily focuses on a particular space, especially slums. These development projects do not affect the mainstream resource allocation from the government (Danquah et al., 2018; Rahman & Ley, 2020; UNDP, 2016). As a result, the mainstream (formal) development process does not address the structural reforms where the resource allocation has been controlled by the dominant social and political structures and is not shared with the underprivileged (Banks, 2008; Brett, 2003; Swapan, 2016).
The authors argue that the myopic approach of seeing the urban poor within a bounded geography (slum) could not improve the service provision to the urban poor. It also did not help slum residents to bring their organisation capacity into the city-wide decision-making process. Urban poor in the non-slum poor settlements are growing and cities need a holistic approach to address urban poverty and service delivery. In the context of growing number of population and positive population growth projection in South Asia, the authors in this article explored how academic research has addressed the issues of slums and the growing non-slum poor settlements. The authors use the bibliometric analysis to identify the research initiatives on slums/informal settlements, and to explore how the academic research addresses the concepts of non-slum areas, which the authors termed as the ‘poor settlements’. This article seeks to shed lights on skewed focus on slums and identify grey areas of academic contributions to study inequality and access to services to urban poor. The central hypothesis of this study is that little focus has been given by national and international agencies to improve the condition of people living in poor settlements, with a corresponding lack of research on this topic.
Study Methodology
This article analyses the contents of scientific articles, book chapters and conference proceedings published from the early 1900s–2019; all material for this bibliometric analysis was extracted from the Web of Science (WoS) database, restricting the keyword search to slum, poor settlements, squatter and informal settlement. The initial search returned 16,281 results which were refined by excluding unrelated WoS categories such as sports sciences, immunology and psychology. Irrelevant source titles, including from 18 journals and 76 categories not pertaining to the scope of the study, have also been excluded. From the remaining total of 3,689 articles, book chapters or proceedings, the first 400 with the highest number of citations have been selected for review, in order to keep the visualisation manageable. The bibliometric analysis is conducted using VOSviewer 1.6.13 which has the functionality of text mining and constructing and visualising co-occurrence of networks of essential terms from a body of scientific literature (Van Eck & Waltman, 2009, 2011). The bibliographic mapping in this study is based on citations, co-citations and co-occurrence to map the extent of scientific literature on slums or informal settlements and poor settlements, with selected articles grouped into five categories based on their citation and co-citation linkage strength. Each categorisation threshold is set to a minimum of 50 relevant articles on the same topic or field of research.
The second stage of analysis identified 750 relevant papers from WoS which were published between 2015 and 2019. A total of 483 papers with at least one citation have been taken for the analysis of co-occurrence using keywords. The parameter set to form a distinct cluster was a minimum of two papers with similar keywords. In addition to the bibliometric analysis using articles from WoS, the study also reviewed a broad range of articles, reports and other documents on slums and poor settlements, to explore the theoretical and practical interventions contemplated and undertaken to identify the academic research on poor settlements in particular.
Slum/Informal Settlements Versus Poor Settlements
Throughout history, different terms have been employed to describe the overcrowded living conditions of slums, such as decaying inner-city tenements, squatter settlements and shantytowns (Khalifa, 2011). The use of the term ‘slum’ can be traced back to the Industrial Revolution in the United Kingdom in the mid-1700s, when millions of people flooded to cities seeking work, setting up home wherever they could. In 1812, the term was coined to indicate a racket or illegal trade (Gilbert, 2007) and gradually shifted to describe all forms of adverse social outcomes such as inadequate housing and sub-standard living quality (Flood, 2002; Prunty, 1998). These deprived areas, where low-income families are compelled to live in unhygienic and very dense, poor quality housing with a lack of basic services, are generally found either within a city or on its outskirts. In regard to developing countries, the United Nations (2002) reported that typically, in addition to tenure insecurity and inadequate space, slums also have a lack of basic services such as water, electricity and sanitation. Such services are not provided by government bodies, partly due to the informal status of the occupants (Durand-Lasserve, 2006; Swapan, 2016). Rather, special types of relationship have been built between the tenants and the landlords where the landlords become the service provider (Rana, 2016; Swapan, 2016). The term ‘informal settlement’ started to replace using the term slum to replace its negative connotation. Finlayson (1978) argues that informal settlement is the result of the inability of urban development programmes to cope with rapid urban growth. UN-Habitat defined informal settlement as the place of tenure insecurity, lack of services and lack of building regulations. While replacing the slum is seemingly less derogatory, ‘informality’ is still understood to mean substandard, illegal or not compliant with building laws and planning regulations.
Physically defining a slum/informal settlement is very complex and further complicated by the fact that there are growing concerns over the development of non-slum settlements (Gilbert, 2007). Slum is considered as one form of informal settlement (Chatterjee, 2019), and it can be extended to any part of the city where real estate speculation for all income levels is present (UN-Habitat, 2015). Informal settlement takes the broader view of natural growth in parts of the city where building regulations have not been maintained. Informal settlement growth has been termed as a process where a settlement grows over time. Chatterjee (2019) has explored in Mumbai that there is a growing number of settlements located adjacent to the slum areas missing the characteristics of slums such as tenure insecurity. People in those areas in Mumbai have been found buying lands and houses or paying regular rents. Settlements in the close vicinity of the slum in Bangladesh have also been enjoying tenure rights over generations.
Better job opportunities, among other factors, are contributing to the ever-increasing numbers of struggling people, from both rural and urban areas who are setting up home in either slum or non-slum poor settlements. This makes the difference between formal and informal settlements often blurred (Durand-Lasserve, 2006). The use of informal settlement is also becoming confusing as some researchers such as Montana et al. (2016), Farouk and Lawson (2014) and Martínez et al. (2008) have used the term ‘non-slum’ to include formal settlements while some other include both formal and informal settlements other than the officially or unofficially recognised slums (Adnan et al., 2018; Ahmad et al., 2013). To differentiate from slums and to avoid the confusion with the informal settlement, the authors in this paper want to designate the non-slum areas as poor settlement. While there is no specific definition of a poor settlement, Fortuny et al. (2011) have added two more characteristics to the definition of slum given by the United Nations (tenure insecurity, lack of basic services): temporary housing materials 1 and susceptibility of flooding. The authors consider poor settlements as sporadic developments around slums or squatter settlements and scattered settlements in urban areas. The authors argue that these settlements may have either (or both) formal and informal characteristics.
Faces and Places of Slum Studies
Much research has been conducted covering almost every aspect of slum life, both in developed and developing countries. Though the literature search was conducted using a combination of keywords such as slums, informal settlements and poor settlements, almost all the influential work was found to be focused on slums. This study grouped the broad areas of scientific contributions on slums into the five most prominent clusters 2 as illustrated in Figure 1: slum/informal development; informality, housing and living quality; community services and mapping; citizenship and governance; and health. The five clusters emerged based on their citation and co-citation linkage strength. To form a cluster, a minimum of 50 relevant articles need be closely linked with each other on a field of interest (based on citation and co-citation strength) Each categorisation threshold is set to a minimum of 50 relevant articles on the same topic or field of research. The cluster names have been picked by the frequent keywords of the cluster articles.

The first cluster defines and redefines slums in developing countries and explores the policy responses to informality, such as slum upgrading and land titling (Roy, 2005); community-based approaches in slum upgradation (Burra, 2005); slum upgradation under changing institutional environment in the neoliberal era (Nijman, 2008); the effect of the judiciary rulings on slum clearance in Delhi (Bhan, 2009); and the evolution of negotiations on plans to redevelop Dharavi, Mumbai (Patel et al., 2009). The issues of governance, social power and justice appear in later studies (McFarlane, 2009, 2011; Roy, 2011). McFarlance (2009) studied in Mumbai to describe the spread of social movements through ‘translocal assemblage’, stressing on the sharing of ideas, knowledge and practices across the sites in a city. As McFarlane (2009) pointed out, urban social movements in Mumbai are mobilised by the educated middle-class activists with relative power and connection to the government, from where the urban poor get benefit from sharing ideas and practices. McFarlance (2009) thus stressed on the assemblage, rather than network, as translocal assemblages can accommodate the exteriority in the process of the production of political stances or pieces of knowledge. In the wake of the aspiration of Delhi to be a global city, Dupont (2011), Ghertner (2011) and Rao (2011) examine the negative implication of slum clearance and the livelihoods of the urban poor. Roy (2011) argues that the informality is also present in wealthy urbanities, as the malls of Delhi’s farmhouses are as illegal as the slums. They are considered as formal through the class power and the state’s endorsement. Therefore, the negative connotation to the informality or slums can also be used for the wealthy communities, and scatteredness or informality cannot be the judgemental factors for receiving services from the state.
The second cluster, as classified by the authors of this study, is related to informality, housing and quality of living and includes studies on housing improvements and living conditions by authors such as Huchzermeyer (2003), and the effect of subsidy for housing and slum upgradation (Mistro & Hensher, 2009). Most of the writing on this cluster has been influenced by De Soto’s (2000) optimistic argument about slums or informal settlements, who sees the informal growth as heroic entrepreneurship in developing countries. A small sub-cluster has studied material and children’s wellbeing in slums and informal settlements (Breiman et al., 2012).
The third cluster is predominantly about the issues of tenure insecurity that are further linked with slum upgradation (Huchzermeyer, 2003; Mistro & Hensher, 2009) and community actions for securing housing (Dupont, 2011; Ghertner, 2011; Rao, 2011).
The fourth cluster shows a distinct research trend which is about development/regeneration, social exclusion, governance and power relations. Literature that falls in this category has been studied predominantly regarding European cities (Amsterdam, Berlin, Madrid, Istanbul etc.). Kuyucu and Unsal (2010) documented the shift of the government approach from the populist to the neo-liberal in urban land and housing markets. He pointed out that large urban transformation projects in Turkey resulted in displacements and did not contribute to improvement in living conditions. Turkun (2011) elaborates the coalition between the state and powerful actors behind the Large Urban transformation projects. He has identified that the rent gaining potential through this association left the historic urban centres in Turkey with the large scale urban poor populations.
The fifth and the final cluster studied is service provision and mapping. This cluster of literature represents both the global north and south. Highly cited articles in this cluster have examined water supply and sanitation in slum areas (Akbar et al., 2007; Mcfarlance et al., 2011); Sanitation and children (Bartlett, 2003); Slum formation (Taubenböck & Kraff, 2013) and mapping as an effective way of service provision (Kohli et al., 2013; Patel et al., 2014; Weeks et al., 2007). This research is about delineating the slum areas for the sake of planning and effective service provision. In this cluster, the researchers have confined the slums within a specific geographical space, either it in the Global South, for example redeveloping Dharavi, Mumbai (Patel et al., 2009); material and children’s wellbeing in Nairobi (Bartlett, 2003); initiatives to identify slums in Bangladesh and India (Dewan & Yamaguchi, 2009; Kohli et al., 2013) or in Global north such as renewal or transformation projects in Turkey or Restructuring in Berlin.
’Slums’ in Disguise of Poor Settlements
Since the highest cited 400 scientific works did not cover the term poor settlements, the authors have searched for more articles that have covered the issues of poor settlements. The scientific contributions on poor settlements have been found circumscribed by the significant scientific influence of slums and informal settlements. The term ‘poor settlements’ has mostly been used as a synonym of the slum, squatter or informal settlements in the literature. For example, the term has been used to study immunisation coverage in the slums of Delhi (Devasenapathy et al., 2016); housing upgradation in informal settlements in Indonesia (Rukmana, 2018); environmental emergencies management in Kathmandu (Giambelli et al., 2016). In Bangladesh, ‘poor settlement’ has been used to study the impacts of sanitation initiatives by NGOs in Dhaka slums (Bilqis et al., 1994); health care situation and social network in maternal and newborn health in Dhaka and Sylhet (Adams et al., 2015; Islam et al., 2016); mapping of slum and poor settlement areas (Hossain & Nazem, 2012); and tenure security and housing investment (Nguyen, 2018).
The authors of this study thus point to the lack of research on poor settlements beyond the slum, squatter or informal settlements. The authors argue that decades of development interventions in slum areas may have put slums in a relatively better position than the scattered poor settlements. Slum-dwellers are more politically aware and are strongly connected with the political process. That also helps in improving their condition.
Changing Faces of Slum Studies: Are We Missing a Large Part of the City?
It is evident that despite the growing number of the population that is taking shelter in the non-slum poor settlements, academic research continues to focus on slums. At the same time, academic practices have been observed as slow in addressing the growing concerns of intra-city inequality in terms of access to services and participation in decision-making.
Unable to find notable work on poor settlements, this section explores the trends of research on slums by analysing the keywords from the 400 highest-cited articles from 1900 to May 2019. Furthermore, to explore the recent research on slums, the study looked into articles published from 2015 to May 2019. The study also compared the research trends between the two time periods of 2015–2019 and 1900–2019.
Based on the co-occurrence analysis, words such as informal settlements, slum and housing remain the most critical keywords in the research domain (Figure 2). The issues of urbanisation in the Global South and poor urban communities in countries like India, Indonesia and Ghana have also been widely studied. The review also indicates that a considerable number of interventions have also been made on water and sanitation issues.

Although the words informal settlements, slums, and housing maintain the importance in the recent research on slum, some new keywords such as water governance, urban governance are gaining more importance (Figure 3). The study of water in slums gathered pace in research in recent times as water is becoming a significant source of inequality. Swyngedouw (2004) argues that water circulation in the cities, like other goods and services, is part and parcel of the political economy of power that gives structure and coherence to the urban fabric. Figure 3 also shows that the integrated approach to study water and governance has become prominent as it is absent in Figure 2, where water, drinking water, water access has been studied disjointly. The link strength between issues with household water 3 and water governance in Figure 2 is weak, which indicates there was very little research that looked at both water governance and water together in slums and informal settlements.

Among the selected articles for this study, about two-thirds of them were published between 2015 and 2019, thus pointing to a change in the research focus. While ‘urban poor’ is very prominent in the overall research domain, this has been studied without close linkages with governance or water governance (1900–2019 period). The notable point during this research period (2015–2019) is that the clusters of water governance in cities, governance and urban poor are in very close proximity.
Despite the growing attention over the service provision, the findings from the co-occurrence keywords have been drawn from research works on slums. The previous section also points out the absence of research on non-slum poor settlements. Taking articles published between 2015 and 2019 into consideration, bibliometric analysis provided nine research clusters (Figure 4). As explored in Figures 2 and 3, current research focuses on water governance, housing and related policy outcomes also present in the current research domain, focusing slum areas. The other two clusters have also been observed as lenient to slum issues in particular. The clusters at the far right side, focus on tenure insecurity and housing improvement (Mehrotra et al., 2018; Nakamura, 2016a, 2016b, 2017); and urban development in informal settlements (Amoako, 2016, 2017, 2018; Amoako & Inkoom, 2017; Grant, 2014) while far-left clusters are about machine learning techniques to identify the slum areas for better service delivery.

Concluding Remarks
This study has explored the nature and extent of academic contributions to slums and non-slum poor settlements. The bibliometric analysis and literature review reveal that slums around the globe have been the centre of attention of research in almost every aspect of slum life. This trend is continuing in the recent times with new topics for slum studies emerging, such as water governance.
The analysis identifies five major clusters of slum literature: theory of slum formation and informality; redevelopment, housing and living quality; community services and mapping; health services, and citizenship and governance. Academic literature on slums has predominantly focused on two phenomena:
As the analysis and discussion suggest, people living in poor settlements have received scant recognition in academic literature. Being scattered and posing some degree of formality (land tenureship), these settlements have been overlooked, mainly due to the focus given to slum or informal settlements. As a result, studies on the service provisions and community organisations are almost non-existent. Few theoretical and empirical studies under the heading ‘poor settlement’ have been found. However, it is apparent that the references were to slums, and that the terms slums, poor settlements, squatter or informal settlements are being used interchangeably in current literature.
The authors conclude that non-slum poor settlements are insignificant and underrepresented in academic research, and argue that the study of inequality should not be confined to a specific area of a city, given that slums accommodate only a portion of the growing number of poor people. This study puts inequality in service access at the core of understanding and visualising the city. Addressing the inequality thus requires understanding how the service delivery and the system of service provisions are in practice in the city. Looking for inequality in a confined place such as slums will only give a fragmented image of the city, whereas the growth of the city in the current world is more dynamic. The study advocates the exploration of inequality in service provision, which should take a broader view to include the poor settlements. Taking tenure insecurity as a pivotal determinant for research and interventions also needs to be reconsidered.
