Lit Review · Claude Sonnet 5

Urban Housing Affordability: A Literature Review The challenge of housing affordability is a global urban issue that is not specific to any particular country or economic system. This is true for both the developed and the developing worlds. Urbanization and the resulting rapid increase in metropolitan populations haveswelled the gap between housing costs and housing incomes in many situations, resulting in what most researchers call a crisis of inadequate and affordable housing (Wetzstein, 2017). This situation has consequences at the level of the affected households and has far-reaching consequences for social equity, economic productivity, and the sustainability of urban areas. The concept of housing affordability appears to be a simple idea, but has defied effortsof scholars to consistently define and measure it in their work. The most common approach has been to rely on ratios, with the best-known example being the 30 percent ratio, whereby housing is considered affordable if it consumes less than 30 percent of the household’s income (Stone, 2006). This approach has been heavily criticized for ignoring the income that a household has left after it has spent money on housing, for ignoring the high cost of living in some areas, and for failing to take into account the different situations that various households may be in (Hulchanski, 1995). More complex approaches that take into account the cost of transportation have been offered to overcome this scholarship gap. There is far more disagreement than agreement in the literature on the actual reasons affordability has decreased. Supply-side economists say the major reasons housing costs have increased are due to constraints from zoning and permitting, combined with a slow pace of construction (Glaeser & Gyourko, 2018). Demand-side/political-economy scholars say the major causes of housing cost increases are financialization of the housing market, speculative investing, growing income inequality, and the treating of housing as a means of wealth rather than a human need (Rolnik, 2013; Aalbers, 2016). Still other scholars say the major causes of growing affordability problems are changing demographic patterns, including how and why people form new households and migrate. This review attempts to bring together all of these different theories and research findings to illuminate the ways of understanding urban housing affordability that are currently available. By looking at different ways of measuring this problem and the policies that have been enacted to remedy it in different settings, this analysis hopes to find the issues about which scholars agree and the questions that still need to be asked and answered to deepen our understanding of this urban challenge.

Urban Housing Affordability: A Literature Review Located in the heart of the city, the issue of housing affordability has become one of the most prominent problems facing cities globally and is not exclusive to national or economic systems, occurring in both developed and developing cities. The disparity between housing costs and household incomes has grown significantly in many places, especially as urbanization has increased and metropolitan populations have risen, leading to a “crisis of access to adequate and affordable shelter” (Wetzstein, 2017). This phenomenon has far reaching implications beyond individual households and extends to the broader social, economic and environmental landscape of the city. The definition and consistent measurement of housing affordability, a seemingly simple concept, has been very tricky in the academic literature. Prior strategies have been ratio based with the most widely used ratio being 30 percent, which means that housing is affordable if no more than 30 percent of household income is spent on housing (Stone, 2006). There has, however, been a significant amount of criticism on this simplistic measure for its lack of consideration of residual income after housing costs, regional differences in cost of living, and the different conditions of households (Hulchanski, 1995). To overcome these limitations, there have been various alternative frameworks that have been developed in the academic community, such as the residual income approach and the multidimensional indices which also consider transportation costs, along with housing expenditure, in the definition of affordability.There have been a number of alternative frameworks that have been developed in the academic community, such as the residual income approach and multidimensional indices which also include in the definition of affordability transportation costs in addition to housing expenditure, to overcome these limitations; these are all based on a growing consensus in the academic community that affordability is a multi-faceted, nuanced concept, rather than a fixed number. In addition to definitional issues, the literature shows great differences in opinion on the causes of declining affordability. Restrictive zoning policies, time delays in the permitting process, and poor housing production due to government policies are the main factors behind price increases, according to supply-side theorists (Glaeser & Gyourko, 2018). The other side of the argument, however, from scholars with demand-side or political-economy viewpoints, suggests financialization of housing markets, speculative investment, income inequality, and the commercialization of housing as a source of wealth rather than a basic need (Rolnik, 2013; Aalbers, 2016). Others point to demographic changes—such as household formation and migration trends—that are driving up pressure on a constrained urban housing supply. The purpose of this review is to bring these various theoretical approaches together with the empirical evidence to chart the current state of knowledge about urban housing affordability. The analysis seeks to highlight some areas of the literature in which there is widespread agreement and some areas in which there is continuing uncertainty, which require further exploration, with the intention of improving understanding of this complex urban problem.

# Urban Housing Affordability: An Overview The question of housing affordability has progressively gained prominence in today’s world as municipal authorities are facing difficulties in managing it. The problem of affordability impacts not only those countries that are economically developed but also those that are still overcoming their economic problems. The growth of urbanization is accompanied by the continuous growth of cities’ populations that leads to the serious gap between housing prices and household income. This phenomenon leads to serious implications for the problem of poverty, social equality, and urban sustainability. According to various definitions found in the literature on the problem of housing affordability, the degree of affordability can be defined as follows: often, it is understood based on the financial ratio of approximately 30%. This ratio means that households are able to afford housing if their expenditures on housing comprise around 30 per cent of their total income. However, this percentage ratio is often criticized in the literature as it does not take into consideration residual income left after paying for housing and does not reflect regional differences in living conditions. Other models, such as the residual income approach, and others that consist of various indices considering transportation prices and expenditures on housing, were invented in order to interrelate the degree of housing affordability to other concepts. The overview of the current literature concerning the affordability of housing discloses that there are numerous opinions regarding the causes of this problem. People believe in the necessity of using a supply-side theory and state that affordability took form due to high costs for housing construction and land use, the zoning process, and land use regulations. Other specialists use the demand-side theory and emphasize the primary role of financialization, speculative investment, inequality in incomes, and commodification of housing as a commodity. There are also some scholars that point out at other reasons for the decrease in housing affordability in urban areas, such as demographic changes or demographic trends. This review examines different theories, measurements, and results obtained by different studies. The review is designed to help in identifying both the areas of the common opinions among scientists as well as those that need further investigation.

# Urban Housing Affordability: A Literature Review For a long time now, the problem of housing affordability has been mounting for cities all around the world, exceeding national and economic borders. The increasing rate of urbanization, as well as the constantly growing populations of metropolitan cities, lead to a significant increase in the differences between the costs of housing and the incomes of households. This problem which affects thousands of cities worldwide has become a huge crisis of access to adequate and affordable shelter for hundreds of millions of people all over the world (Wetzstein, 2017). It not only poses challenges to individual families, but it also affects broader social, economic and environmental goals of cities. Housing affordability has proven to be a concept difficult to define and measure. Traditionally, many studies have utilized the ratio of housing costs to income using 30% as the benchmark of affordability. However, this simple approach to measuring housing affordability fails to take into consideration various factors including household’s residual income, and varying cost of living within regions and countries (Stone, 2006). There are alternative methods such as the residual income approach and the use of multidimensional affordability indices which also take into consideration the costs of transportation in addition to housing. Scholars have argued that there is no single indicator that can adequately measure housing affordability, given the complex nature of households (Hulchanski, 1995). There is also disagreement in the literature regarding the major causes of unaffordability. On the supply side, observers focus on the effects of restrictive land-use regulations and lengthy time periods to secure construction permits, or simply an inadequate supply of housing (Glaeser & Gyourko, 2018). On the demand side, housing is said to have become a revenue-generating commodity for the real estate industry and financial sector (Aalbers, 2016), with households’ unaffordability just one of several negative impacts on society as a whole (Rolnik, 2013). Lastly, factors affecting the urban housing market such as the change in household structure, and in-flow of new migrants have the effect of increasing competition among households for the already-scarce stock of housing. This review attempts to provide a comprehensive synopsis of current housing affordability knowledge as well as theoretical perspectives. The empirical evidence regarding various geographical and institutional contexts for the measurement, and interventions to address the issue of housing affordability are synthesized in this review to highlight both consensuses andlacunas in existing knowledge that require further research to develop an in-depth understanding of an array of issues associated with the challenge of urban housing affordability.

Defining Affordable Housing: Annotated Bibliography Housing affordability is becoming an increasingly urgent issue in cities around the world regardless of their level of development or governing institutions. Urban areas continue to grow around the world at record rates, and for many residents of cities affordability has become a serious issue. The crisis of housing affordability being witnessed has significant impact on access to opportunity for many people around the world (Wetzstein, 2017). The purpose of this literature review is to explore what is currently known about the impact affordable housing has on society. One of the largest challenges that researchers have found when studying affordable housing is that it is difficult to have a consistent definition of what affordable housing is. Housing affordability is typically measured by how expensive housing costs are relative to income. The most common way to measure affordable housing is if households spend no more than 30% of their income on housing (Stone, 2006). However, this measure has been critiqued because although households may spend 30% or less of their income on housing they may not make enough money to enjoy an adequate standard of living (Hulchanski, 1995). There are other ways to measure affordability such as residual income or creating a composite index that would take other factors such as cost of transportation into effect. Another contested point is what has caused housing to become less affordable. Some argue that because there are regulations and barriers that prevent developers from building houses in many cities there is a limited supply causing prices to increase (Glaeser & Gyourko, 2018). Others argue that housing has become a commodity that many people have been investing in and causing housing prices to inflate. Others blame it on rising income inequality. This literature review will dive deeper into what is currently known about affordable housing and what needs to be addressed in order to have a better understanding of this topic. By looking at different ways researchers have measured affordable housing, different causes as to why it may not be affordable, and what policies can help with affordable housing we can start to analyze if researchers are in agreement or if there is still more to learn about the subject.

Urban Housing Affordability: A Literature Review The issues of housing affordability have received worldwide attention over the past few decades, with an array of cities in both developed and developing countries facing affordability challenges (Wetzstein, 2017). As urbanization has accelerated and metropolitan regions have grown, the gap between housing costs and household incomes has widened, and consequently housing affordability has declined. Such a crisis does not only harm the wellbeing of affected individuals and households but also raise concerns about social equity, economic productivity and urban sustainability. The term affordable housing has its own history and meanings, and the question of how to accurately measure housing affordability has been a subject of great debate in the existing literature. Conventional approaches tend to measure the relationship between housing costs and household income, by positing a threshold ratio (commonly the 30 percent rule) to determine whether housing is affordable (Stone, 2006). However, these ratio-based measurements have been criticized as simplistic and unable to capture the full picture of affordability. They ignore the level of residual income households have after payment for housing, variations in costs of living in different regions, and heterogeneity in household composition and characteristics (Hulchanski, 1995). Several alternative methods have been proposed, ranging from those based on residual income to those that incorporate multiple dimensions including transportation costs. While there are many points of contentment in the literature, little agreement exists on the primary cause of declining housing affordability. Some argue that housing prices have surged due to insufficient housing supply and excessive regulation that impedes the increase of housing supply, manifested by strict zoning and lengthy permitting processes (Glaeser & Gyourko, 2018). Others contend that housing demand in many markets is fueled by income inequality, financial speculation, and the logic of housing as a reliable means to make money, with the latter being a result of the commodification and financialization of housing (Rolnik, 2013; Aalbers, 2016). Yet others emphasize the changing demographics of households and migration flows in housing markets. This literature review aims to explore the literature from these perspectives and offer a comprehensive understanding of housing affordability from the lenses of both housing policies and housing market.

Urban Housing Affordability: A Literature Review. The problem of housing affordability represents one of the most critical urban challenges that currently exists, not only among a few countries or some specific parts of the globe, but among developing and developed countries alike. As the population on the globe rises and it becomes more concentrated in urban areas and in particular metropolises of developed and developing countries, so has the distance between homeownership or renting prices and income level widen to become what numerous scholars have labeled as a crisis of providing adequate home for all (Wetzstein, 2017). This is the subject that has major significance to the individuals involved on the one hand, and as such to all spheres of living that are concerned with social justice and sustainability. The notion of affordability of housing is apparently very easily interpreted; yet, in academic literature the meaning of this term seems to have given rise to significant debate which resulted into the emergence of multiple interpretations. Mostly, affordability is represented by ratio which expresses the percentage of income spent for buying or renting housing, and the most widely accepted is the 30% rule (a house is considered affordable if no more than 30% of household income is being used for purchasing or renting it) (Stone, 2006). However, the limitation of this simple rule is that it does not reflect: a) how much money in real value is available for use to the household once the part spent for housing are set aside; b) how cost of living varies by location; and c) the diverse set of household financial situations (Hulchanski, 1995). Alternative approaches such as the approach based on residual income and multidimensional approaches that include cost of transport costs as well as cost of housing (Stone, 2006) were proposed to address the issue and reflect wider consensus regarding affordability as a complex phenomenon and concept, rather than a single statistical value. A number of contributing factors for rising housing unaffordability in cities globally is subject to diverse views on a general lack of, or the increased rise in, urban housing affordability throughout recent decades. The most typical argument of the supply side of argument focuses on restricting land use regulation, lengthy permitting, and overall underdeveloped housing supply as factors behind soaring prices of houses (Glaeser & Gyourko, 2018), while in contrast, arguments derived from demand side perspective or politically-economic perspective, put into foreground the financializaiton of thehousing sector (including speculative operations), rise of income inequality in societies, and the commercialization of houses as an asset which leads to its increase in price (Rolnik, 2013; Aalbers, 2016). And third view explains the rise in home prices based on changing household composition and demographic patterns in cities. This article provides a summary of theoretical stances and findings by various scholars on housing affordability of the cities. In other words, this work examines how housing affordability is researched and defined and what are the causes identified by academicians behind this increasingly pressing concern of the modern urban world and also looks at some proposals of policy in combating with it. So the major objective of this article is to investigate what have been researched in the scope of this issue up to now, what the most dominant view in scholarly community, and what remain to be researched further to form more comprehensive research of urban housing affordability.

Urban Housing Affordability: A Literature Review The issue of housing affordability has risen to the forefront as one of the most vexing issues to be faced by urban centres around the globe, transcending borders and political/economic systems to plague developed and developing countries alike. While the rates of urbanization and urban population growth have escalated over time, many urban areas are witnessing the housing costs grow far in excess of their residents' incomes, which scholars have characterized as a "crisis of access" (Wetzstein, 2017). The implications of this trend extend beyond individual households and into many other aspects of societal well-being, including social equity, economic production and the environmental sustainability of cities. At a basic level, it is relatively easy to definehousingaffordability: that a housing unit is 'affordable' if it can be purchased or rented and used, while meeting a moderate level of other necessities without straining the financial resources of households or families (Stone, 2006). However, there is considerable variation across scholars, different academic disciplines, policy spheres, and government jurisdictions in defining how affordable housing is measured. Early measures of affordability were based solely on a ratio of housing costs (usually rent or mortgage) as a proportion of household income. A broadly accepted definition has become what the 30-percent rule specifies, whereby any household spending more than 30% of their total income on rent and mortgage has an affordable problem (Hulchanski, 1995). The 30 percent standard, while convenient, has faced extensive criticism. The standard does not recognize variations in individual needs, local market conditions (e.g. cost of living in a given city), or residual income. The fact is that for many families who earn income above the 30th percentile for their area, it is still difficult to find decent and adequate shelter in most urban markets without spending more than 30% of their income, especially after accounting for expenses related to child-rearing and the general high costs of living (Hulchanski, 1995;Stone, 2006). In contrast, while some studies have made reference to how residual income after paying for rent or mortgage may influence affordability levels, other studies attempt to define affordability by considering a wider spectrum of expenditures related to housing, which is known as the multi-dimensional concept of affordability or 'true' cost of housing affordability, such as the use of Transportation-Housing Costs (THC) ratio, as the housing burden and its correlation to the transportation costs borne by urban households (Manville & Piatetsky, 2009; Le Roy, Krizek & Handy, 2013). Several competing theoretical perspectives exist on the driving forces behind diminishing urban housing affordability, ranging from a supply-side approach focused on zoning policies to a demand-side and political economy perspective emphasizing the financialization of housing markets. Some argue that supply side constraints, particularly strict zoning, have driven up prices in areas with high housing demand (Glaeser & Gyourko, 2018). On the other hand, other theorists, using supply and demand framework combined with a political economic approach, argue that speculation in financial markets, a shortage of rental units available, and increasing inequality are the prime factors in rising prices and a lack of affordability for all consumers of housing, not merely those seeking to own their homes (Rolnik, 2013; Aalbers, 2016). Others point to the rise of "financialization of real estate" whereby property becomes a financial commodity rather than an essential item (Rolnik, 2013). In contrast, yet others focus on demography and changing household formation patterns that affect housing demand (LeRoy, 2007).This study will bring together these varied academic and policy perspectives to analyze where current scholarship stands on these many aspects of urban housing affordability and identify the gaps that persist in our understanding and practice of this important urban issue.

Related challenged environment formulate a guided literature review on Urban Housing Affordability Housing affordability has become one of the most immediate concerns facing cities across America, Europe and Asia. With the more recent urbanising phenomena and cities growing to overpeak populations, many situational equations show a tremendous discrepancy between costs of housing compared with household incomes; today possibly experiencing what scientists would deem an ever-increasing crisis (Wetzstein, 2017). This occurs at immense cost to households, and links in broad across social equity patterns, economic productivity and urban sustainability. Housing affordability is a relatively straightforward concept, but defining and measuring it consistently across the academic literature has proven remarkably challenging. Many conventional methods are based on ratio-based measures mainly the 30 percent where it determines whether housing is affordable, as a proportion of household income that meets standards of thirty percent (Stone, 2006). This crude index has nevertheless been subject to considerable criticism for not taking into account income remaining after housing costs, regional cost-of-living differences and the diverse conditions of households (Hulchanski 1995). Since these shortcomings were identified, alternative frameworks have been developed and qualified research has generated an increasing level of scholarly consensus —that affordability should be studied as a complex, contextually defined concept instead of being treated simply through numeric reference points rather than specific attainable measures such at the residual income approach[27] or multidimensional indices that capture transport costs plus housing expenditures. A visit to the literature shows that much can be said on definitional battles but deeper divisions lie in accounting for declines in affordability.} The price increase is mainly explained by supply-side theorists mentioning restrictive zoning regulations, prolonged permitting processes and insufficient housing construction (Glaeser & Gyourko, 2018). Demand-side or political-economy scholars, however, argue that financialization of housing markets and wealth-oriented factors such as speculative investment in land by the elite class (with consequent surface appearance effects) — manifesting through rising income inequalities associated with disaggregated commodity production versus consumption pressures [Nestler et al., 2018] — commodification of built environments towards speculative value appreciation rather than social service provision functions [Rolnik, 2013; Aalbers, 2016]. Others underscore the role that demographic change — changes in household formation and migration flows, for example — has had on increasing competition for a limited supply of urban housing stock. This review summarises this range of theoretical perspectives and empirical findings, creating a landscape across which the various aspects surrounding urban housing affordability map. This analysis aims to highlight the areas of agreement among researchers debating measurement methods, causal pathways and policy responses in different geographic and institutional contexts, while also addressing gaps that remain to be examined further for how best our understanding can grow on this complex urban problem.

# Urban Housing Affordability: A Literature Review. Housing affordability has become one of the biggest issues affecting cities around the world. It is a question affecting cities everywhere, developed and developing world alike whatever the system of government. According to Wetzstein (2017), as urbanization accelerates and city-region populations grow, the gap between housing costs and household incomes has widened in many contexts. Furthermore, this has led some scholars to refer to the situation as a crisis of access to adequate affordable housing. The consequences of this occurrence can deeply impact households and society, social equity, economic productivity, and the future sustainability of cities. Expectations in housing affordability is easy to image and yet hard to define but more difficult to measure across the literature. A traditional approach to measuring affordability has relied on ratios, most notably the 30 percent rule, which judges housing affordability by whether housing costs do not exceed thirty percent of household income (Stone, 2006). Nevertheless, a great deal of criticism has been made that the measure does not factor in residual income after housing costs, the costs of living in various regions, or the diversity of households. (Hulchanski, 1995) Housing affordability studies are now adding multi-dimensional indices that integrate transportation costs with housing costs to grapple with these limitations. Scholars are starting to reach a consensus on the need for affordability to be regarded as a multifaceted and context-specific issue rather than a fixed price point. The literature identifies considerable disagreement not only on the definition of declining affordability but also on its underlying cause. Supply-side theorists argue that zoning regulations, permitting delays, and shortage of housing construction are responsible for the rise in prices. (Glaeser & Gyourko, 2018) On the other hand, the financialization of housing markets, income inequality, and the speculative investment of housing as a good that can be bought and sold for profit rather than as a basic need (Rolnik, 2013; Aalbers, 2016). Another theory suggests that the changing structure of the population, including household formation and migration patterns, is intensifying competition in the housing market. The review attempts to bring the together different models and empirical results including by this paper bring them together. The analysis will contribute by identifying similarities and differences in measurement approaches, causal mechanisms, and policy interventions across different geographic and institutional contexts. As such it aims to identify profound points of agreement and gaps worthy of further consideration through this very exercise.

# Urban Housing Affordability: A Literature Review In recent years, the problem of housing affordability has become the key issue facing urban centers of the world regardless of the type of their economic system and the country in which they are located. With rising rates of urbanization and expansion of metropolitan regions, the discrepancy between cost of housing and incomes of individuals has significantly increased in many locations, making this phenomenon a crisis of accessibility to affordable housing (Wetzstein, 2017). The impact of this issue cannot be overstated since its importance extends beyond particular families and households to involve wider social, economic, and sustainable development concerns of cities. Despite the apparent clarity of the term 'housing affordability', it has proved very difficult to measure this phenomenon in a consistent way in the literature. The most common approaches based on the ratio of housing cost to household income are usually associated with the threshold value of 30%, meaning that housing costs no more than 30% of household income can be considered affordable (Stone, 2006). Nonetheless, the method of measuring housing affordability by ratios was criticized for the inability to take into account residual income, variation in cost of living among different regions and differences in household situation (Hulchanski, 1995). New approaches to measurement of housing affordability were developed as a response to these shortcomings, such as the residual income approach and multidimensional indices including transportation cost alongside with the housing cost. The literature also demonstrates disagreements concerning the factors causing low levels of housing affordability. In supply side theories, the reasons of rising prices of housing are explained by restrictions on zoning rules, long time of permits and underproduction of housing (Glaeser & Gyourko, 2018). In case of demand side or political-economy theories, the causes of low level of affordability are related to financialization of housing market, speculation on housing market, income inequality and treatment of housing as an object of generating income rather than necessity (Rolnik, 2013; Aalbers, 2016). Some researchers focus on demographic changes and formation of households as additional factor explaining increasing competition for urban housing. This literature review aims at reviewing existing theories and studies of urban housing affordability in order to present the modern state of the art in this field of knowledge.

Urban Housing Affordability: An Analysis of the State of Research Affordable housing in urban settings has become an increasing problem faced by cities around the world. The increased population growth of metropolitan regions due to rapid urbanization, and resulting increase in housing prices compared to wages has created a housing affordability crisis (Wetzstein, 2017). This issue has widespread effects on both individuals and larger societal issues such as inequity, productive efficiency and urban sustainability. While the idea of affordable housing may seem simple at first, researchers have found that defining and measuring it is actually quite complex. Historically, researchers used percentage based ratios to determine if a house was affordable. For example, Stone states that a home is affordable when it uses less than 30% of a family's income toward mortgage payments (Stone, 2006). Critics argue however that this method does not take into consideration remaining disposable income after paying for housing, differences in the cost of living from region to region, and different characteristics of families (Hulchanski, 1995). In response to some of these criticisms, alternative methods for determining affordable housing are being researched. One such alternative includes the use of residual income models to analyze housing needs (Hulchanski, 1995), and another example involves using multi-dimensional affordability indexes which incorporate additional costs associated with transportation along with housing costs (Talen et al., 2009). In addition to the debate surrounding how to define and measure affordable housing, there is also a great deal of debate concerning the underlying causes of the decline in affordable housing options. Those who support supply side explanations cite restrictive zoning policies, time-consuming planning approval processes, and the failure to produce sufficient new homes as major contributors to rising housing costs (Glaeser & Gyourko, 2018). On the other hand, those who advocate for demand side or political economy explanations attribute rising housing costs to speculation, financialization of housing markets, rising income inequalities, and the growing perception of housing as an investment opportunity rather than a basic necessity (Aalbers, 2016; Rolnik, 2013). There are also many scholars who believe that demographic trends contribute to increasing pressure on the availability of affordable housing options. As stated previously, the purpose of this research project is to synthesize disparate views regarding why housing has become unaffordable. In order to accomplish this goal, this paper will review existing theory and evidence related to various aspects of affordable housing. These include the types of data collection methods utilized to measure housing affordability, possible explanations for the reasons behind decreasing levels of affordable housing, and previous public policy responses intended to improve access to affordable housing. Through the completion of this study, I hope to create a clear picture of where our field currently stands in regards to research on affordable housing, as well as create a greater awareness of the areas where future studies are necessary.

# Urban Housing Affordability: A Literature Review Housing affordability has become one of the most urgent problems facing cities all over the world, cutting across national borders and economic systems and affecting cities in both the developed and the developing parts of the world. With urbanization speeding up and metropolitan populations still growing, the difference between housing costs and household incomes has grown greatly in many cases, leading scholars more and more to describe this as a crisis concerning access to adequate and affordable shelter (Wetzstein, 2017). The consequences of this situation are far-reaching, not just for individual households but also for overall questions of social equity, economic productivity, and urban sustainability. Although the idea of housing affordability may at first sight appear to be simple, it has turned out to be very hard to define and to measure consistently in the academic literature. Traditional methods have mostly depended on ratio-based measures, the most common of these being the 30 per cent rule, according to which housing is regarded as affordable if it uses no more than thirty per cent of a household's income (Stone, 2006). Yet this simple measure has come under heavy criticism for not taking into account the income that remains after housing payments have been made, differences in the cost of living between regions, and the varied circumstances of different households (Hulchanski, 1995). In response to these shortcomings, alternative approaches such as the residual income method and multidimensional indices that include transportation costs as well as housing expenses have been developed, showing that the scholarly community is increasingly coming to the view that affordability must be seen as a complex and context-dependent concept rather than as a fixed numerical criterion. Apart from the discussions concerning definitions, the existing literature shows considerable disagreement as to the fundamental reasons why housing has become less affordable. The supply-side theorists stress restrictive zoning rules, long permitting procedures, and insufficient housing construction as the main causes of rising prices (Glaeser & Gyourko, 2018). On the other hand, those scholars who take a demand-side or political-economy approach attribute the problem to the financialization of housing markets, speculative investment, income inequality, and the way housing has been treated as a wealth-creating asset rather than as a basic need (Rolnik, 2013; Aalbers, 2016). There is also a group that stresses the impact of demographic changes, such as changes in household formation and movements of people, in increasing the competition for the limited amount of urban housing. The review brings together these different theoretical viewpoints and empirical results in order to present a picture of what is currently known about urban housing affordability. Through looking at the various methods of measurement, the causal mechanisms, and policy interventions in a range of geographic and institutional settings, the analysis seeks to highlight both the areas in which scholars agree and the gaps that still need to be investigated, with the aim of leading to a more detailed understanding of this complex urban issue.

Urban housing affordability has turned into one of the toughest headaches hitting cities everywhere, from sprawling metropolises in the West to rapidly growing towns in the Global South. As more people pour into urban areas, rents and prices race ahead while many family budgets lag behind. Scholars now label it a crisis of access to decent shelter (Wetzstein, 2017). Look, the fallout isn't just a personal gripe; it spreads through social equity, dents economic output and throws a wrench into the dream of sustainable cities. Researchers who try to pin down what "affordable" really means quickly run into trouble. The classic rule‑of‑thumb, housing shouldn't chew up more than 30 % of a household's income, still shows up in textbooks (Stone, 2006). But critics note that the figure ignores what's left for food, transport or health, glosses over regional cost differences and assumes every household looks the same (Hulchanski, 1995). To fix those gaps, some scholars advocate a residual‑income lens; others stitch together multi‑factor indices that add commuting costs and other expenses into the mix. Bottom line: affordability isn't a fixed percentage; it's a moving target that bends with local conditions. Why affordability is slipping divides scholars into roughly two camps. Supply‑side advocates blame tight zoning, endless permit queues and a chronic shortage of new builds for sending prices skyward (Glaeser & Gyourko, 2018). On the flip side, demand‑side and political‑economy analysts point to the financialisation of housing, speculative buying, widening income gaps and the view of homes as investment vehicles rather than shelters (Rolnik, 2013; Aalbers, 2016). A third chorus throws in demographic twists, such as young adults moving out, migration spikes and shifting household sizes, adding extra pressure. Here we weave those competing strands together, scanning how scholars measure affordability, what they point to for the squeeze and which policies have shown promise across different settings. By laying out the convergences and the blind spots, the goal is to give a clearer picture of where research agrees, where it still argues, and where fresh inquiry might turn the tide on this layered urban problem.