This entry focuses on scientific research on cities in the modern age. For research on the formation of the first cities in history, see the entry Civilization.

                     Early Sociological Research of City

In the city of Manchester, Friedrich Engels conducted one of the first sociological empirical research; and presented the results in the book The Condition of the Working Class in England (1845). For research purposes, Engels used several different methods of data collection: he surveyed working households in Manchester, used official statistics, studied the reports of parliamentary commissions, interviewed factory inspectors, etc. The period of the middle of the nineteenth century in England was marked by rapid industrialization and a sharp increase in the number of industrial workers, which was especially evident in large industrial cities such as Manchester. The housing situation in Manchester, in that period, was very bad, and it was especially pronounced among a large number of Irish immigrants. Engels notes that the new industrial cities were built by industrial and financial speculators, with the sole goal of creating as much profit as possible, regardless of the living conditions of those who work and live in those cities. Engels' research showed that industrialization caused a huge deterioration in the living conditions of workers. Housing conditions were so poor that most working families lived in only one room, in very poor-quality buildings; their clothing and food were in extremely dire condition, and the mortality of children and adults was several times higher than that of the rest of the population; diseases and infections were very widespread; workers did not have access to even the most basic health and educational resources; the average working day lasted twelve hours; even the children did the hardest jobs. Engels noted that industrialization had led to the creation of, what he called, a "reserve army of labor" made up of unemployed workers. This reserve army of labor grows during periods of economic crisis and decreases during periods of economic growth. The reserve army of labor enables employers to easily find workers in periods when the economy is working well and to easily fire workers when there is a period of crisis. Engels' data indicate that in that period there were over a million and a half people who belonged to the reserve army of labor, who, in order to survive, did the dirtiest jobs (e.g. collecting horse dung on the streets) or begging. Workers also differ from the bourgeoisie in cultural features: they have different dialects, different values ​​, and different social and political attitudes.

Fustel de Coulanges, in The Ancient City: A Study on the Religion, Laws, and Institutions of Greece and Rome (1864), argued that the essence of the city isn’t only in its spatial characteristics – streets, buildings, and bridges. the essence of the city was its ‘religious’ nature, as when in historical times various tribes agreed to ‘unite’ they founded the city as a form of religious sanctuary where they could do common worship.

Ferdinand Tönnies, in Community and Society (1887), presented the dichotomous division into "community" (Gemeinschaft) and "society" (Gesellschaft) as the two main ideal types of human groups. The community is the first, in the historical sense, and is a place of common life, and the best examples of the community are household and family, neighborhood, village and rural life, and ethnic communities (which are connected by customs, language, and religion). Society emerged with the rise of urban culture, customs, and attitudes of the capitalist class (the third class at the time of the French Revolution). Society is characterized by „rational will“ (Kürwille), and the main example is the city.

Georg Simmel, in his article “The Metropolis and Mental Life” (1903), asserts that people in the cities are bombarded with a multitude of activities, events, images, and impressions, which makes it impossible for individuals to respond to all of them. People in urban environments have to protect themselves from the various and multiple 'unexpectedness of violent stimuli', so they become disinterested, emotionally distant, and adopt a 'seen-it-aIl-before' attitude. Business and financial institutions, which are centered in cities, also demand that people develop punctuality and a rational and instrumental approach to social relations.

Jane Addams, In the book The Spirit of Youth and the City Streets (1909), presents the thesis that city life destroys the spirit of youth, and that it is necessary to introduce programs of games and entertainment in which the spirit of democratic cooperation, free speech, and collective action will develop. In the book, The Delinquent Child and the Home (1912a), Sophonisba Breckinridge shows that poverty and life in overcrowded urban neighborhoods are the main sources of delinquent behavior in children. She also reveals how delinquent children, from different classes, experience different fates - while children from poor families often go to juvenile correctional facilities, at the same time, children from rich families are sent to expensive boarding schools. Emily Green Balch, during the research for her book Our Slavic Fellow Citizens (1910), stayed in several cities, in the neighborhoods where Slavs lived, and traveled around Eastern Europe to get to know the Slavic countries firsthand.

Approach to the City of the Chicago School of Sociology

The Chicago School refers to the work of authors associated with the University of Chicago, especially during the period 1915–35. Their main focus was urban sociology and they used the city of Chicago as a social laboratory, because, at that time, Chicago was one of the biggest cities in the USA with a wide variety of social problems (crime, delinquency, homelessness, class strife, etc.), and populated with people of various ethnic and racial background. This group of scientists pioneered the use of new empirical, qualitative, and quantitative, research methods. With the use of new methods came a new theoretical approach that members of the Chicago School wanted to apply to wider society.

Robert Park and Ernest Burgess jointly published two books that are key to the formation of the Chicago School of Urban Sociology - Introduction to the Science of Sociology (1921) and The City (1925). These two books laid the theoretical and methodological foundations for the study of urban social phenomena. Park viewed sociology as a "natural science" that should study the relationships and processes that take place between different communities in society. Influenced by Simmel's teaching, Park adopted the view that social interaction should be viewed as a key sociological category. He formulated his sociological approach known as "human ecology". Human ecology is a science that studies the action of forces that, within the natural area of ​​human habitation in the city, lead to the creation of typical groups of individuals and institutions. The city is a product of human nature, a state of mind (attitudes and feelings) that is maintained through customs and traditions. The city represents the unity of moral, natural, and ecological order. A city is a place of the creation of a new moral order. The city shattered the traditional moral order and led to the creation of a new order based on individual freedom, solidarity, and common interests. The main natural factors that affect human ecology are: the physical and administrative division of the city into urban areas, traffic and communication technologies, and the economy based on the division of labor.

Due to the social and technical division of labor city is going through changes: specialization and rationalization of activities, creation of professions and professional organizations, and the growing predominance of secondary over primary relations between individuals. The physical and moral organization of the city act on each other and shape and change each other. "The organization of the city, the character of the urban environment and the discipline which it imposes is finally determined by the size of the population, its concentration and distribution within the city are" (Park, 1925). The city leads to the breakdown of the traditional way of life, close neighborly relations are lost, and people live in anonymity. The anonymity and intensity of city life, and especially the focus on work, earning money, and economic relations, has a devastating effect on the form and function of church, school, and family institutions. Traditional forms of social control are losing their significance, especially in the communities of newly arrived immigrants. Changes in the economic, moral, and interpersonal relations in the city have led to the emergence of many social, moral, and mental disorders. The most significant negative consequences of the urban environment are: crime, alcoholism, homelessness, juvenile delinquency, etc.

In The City (1925), Park and Burgess used ecological maps an analytical tool for processing this data, the most famous of which is the one on concentric ecological circles in Chicago. Burgess and Park presented the American city as an ecological structure - a set of localized and isolated zones, each with its own category of the population. These zones often have the shape of concentric circles, so this model of urban development is known as the theory of concentric zones. There is a business zone in the center, outside it is a transition zone characterized by ghettos, slums, and crime; the next is the working-class residential area –populated by second-generation immigrants. Outside of these is the residential zone, and the last is the suburban zone. Urban zones are going through their own evolution, and the main driving force of that evolution is competition. People are fighting for land and other urban resources within the city. City districts and neighborhood relations in them operate relatively independently of the wider physical and social urban environment. A big problem for many cities is the class and/or racially isolated neighborhoods, known as ghettos. Within such ghettos, a specific moral order is often formed.

Louis Wirth greatly contributed to the sociological approach of the Chicago School with article "Urbanism as a Way of Life" (1938). In that article Wirth partially deviates from the classical ecological approach of Park and Burgess and introduces a synthetic approach, combining their ecological approach with Simmel's sociological approach. Wirth, at first, wants to introduce a sociological definition of the city. He recognizes that cities are often the centers of the economic, political, intellectual, and cultural life of a society. However, he believes that the sociological definition of the city must start from the specific characteristics of the city, and that is a special way of human association that takes place in the city. He calls this specific way of human association in the city urbanism, while under urbanization he denotes the process during which urbanism spreads to other settlements and areas. The sociological definition of a city should include a way to study the variations that exist between different cities. Variations in the size, density, and function of cities are great, and it is especially harmful to equate urbanism with the development of capitalism and industrialization. Thus Wirth comes to the definition of the city: "For sociological purposes a city may be defined as a relatively large, dense, and permanent settlement of socially heterogeneous individuals" (Wirth, 1938).

For Wirth's definition of the city, the most important is the great and specific heterogeneity of the individuals who live in it, and in that sense, he notes that the city has always been a place where different cultures and races merge. With the increase in the population and the population density of the city, there are increasing individual variations in the inhabitants. At the same time, the importance of family and neighborly ties is diminishing, while competition and formal control mechanisms are becoming more important than solidarity relations. Human relations, in a big city, are primarily secondary, and interdependence is limited to fragmentary activities. This leads to the fact that the relations of the people in the city are, above all, utilitarian, impersonal and transient, restrained and indifferent. Individuals in the city have a greater degree of individual freedom, but they lose the sense of common moral connection, so they can easily enter a state of anomie. There is a growing division of labor and specialization in cities, while economic relations are becoming exclusively monetary. The patterns of consumption of goods, services, and cultural content of the inhabitants of the city are very different in relation to the inhabitants of the village. Although the income of urban residents is, on average, higher than the income of rural residents, their costs are higher, and housing and communal costs are especially high. Big cities also tend to be spatially separated because people of homogeneous status tend to live in the same parts of the city. A special type of spatial segregation is one on ethnic and racial grounds. Spatial segregation, great social differences, competitive spirit, segmental personal relationships, the fast pace of life, and high population density contribute to the creation of nervous tension and frustration among the city's residents. This leads to an increase in social pathology in cities - crime, delinquency, divorce, etc. That is why it is very important to introduce official mechanisms of social control in the city. Educational institutions, cultural institutions, mass media, civil and voluntary organizations, and political propaganda contribute to equalizing individual differences between the inhabitants of the city.

Chicago School on Slums, Homelessness, and Crime in the City

Louis Wirth wrote the book Ghetto (1928), where he studied the life of Jewish immigrants who lived in two city districts of Chicago. Wirth called one city district a "ghetto", comparing it to the real ghetto in which Jews lived in medieval Frankfurt. He believed that the experience of living in medieval ghettos, in which Jews were forced to live in isolation, imprinted the "ghetto experience" on the Jewish mind, which in the United States also, now voluntarily, began to live in isolated neighborhoods. Wirth believed that, with the increase in the assimilation of immigrants, their residential mobility also increased. In a similar vein as Wirth, Harvey W. Zorbaugh conducted empirical research on the slums in Chicago and wrote about it in the book The Gold Coast and the Slum (1929).

William Foote Whyte did empirical research in Boston, in a slum where Italian immigrants lived. His research method was participatory observation. He lived with an Italian family and observed the daily life of the residents of that neighborhood. This allowed him to focus more closely on the goal of his research, which was the activities of members of juvenile gangs. This research resulted in the very influential book Street Corner Society: The Social Structure of an Italian Slum (1943). Observing the gang members, but also the wider immigrant society, Whyte discovered a culture that had a special structure, and was caused by forced isolation and poverty. In addition to scientific research, Whyte has been involved in advocating for solving the problems of poverty and poor working conditions in slums.

Nels Anderson's first book, The Hobo: The Sociology of the Homeless Man  (1923), which dealt with the homeless in Chicago, was the fruit of one of the first participatory studies, as a research method in sociology, because the author himself spent a lot of time on the street with the homeless themself. The period of industrial development that spread from the east to the west of the USA caused the need for occasional and seasonal work, which led to an increase in homelessness because this type of work was neither safe nor sufficient for a normal life. Anderson discovered that homeless people have different economic and ethnic backgrounds and that the reasons for falling into a state of homelessness are different.

In The Negro Family in Chicago (1932) Franklin Frazier studied the migration, and its consequnces, of African-Americans to Chicago. By the time Frazier began his research, the migration of a large number of African-Americans from the rural south to the industrialized urban centers of the north had been going on for half a century. The difficulties that African Americans have experienced in adapting to living conditions in new environments are the cause of crime, vice, and delinquency among African Americans. In his opinion, the most important thing for the progress of African Americans is to build racial consciousness, which would not be aimed at glorifying "black" culture but would be directed toward the pragmatic goals of achieving socio-economic progress. 

Clifford Shaw and Henry McKay, in the book Juvenile Delinquency and Urban Areas (1931), explore the distribution of delinquency in different parts of Chicago in the early twentieth century. They found that delinquency is increasing in neighborhoods away from the city center and that some neighborhoods have had high rates of delinquency for decades, even though ethnic composition has changed significantly in the same neighborhoods. Neighborhoods with high delinquency rates had high rates of adult crime, tuberculosis, and infant mortality. Shaw and McKay created an environmental model to explain juvenile delinquency. They observed the increase in delinquency in the context of the growth of the city, because with that growth comes the formation of neighborhoods with specific physical, social, economic, and cultural characteristics. The neighborhoods, where the population is declining, where poverty is widespread, and where a large proportion are immigrants and African-Americans, are most affected by delinquency. As a result of these factors, togetherness, and common goals are declining, leading to a reduction in the influence of institutions and social control. All these circumstances have led to the existence of opposing value systems. The decline in the community's ability to informally control crime has led to the formation of a criminal subculture. Delinquent subcultures, peer pressure, and the need to belong to a group were key factors in the development of delinquent behavior. For young people, belonging to delinquent groups meant the possibility of achieving goals that they could not achieve otherwise. As a solution to these problems, the authors proposed the implementation of programs that would unite and strengthen the community and social life in it.

Frederick Thrasher’s book The Gang: A Study of 1,313 Gangs in Chicago (1927) was the first thorough study of a gang of minors in a large city. Thrasher used a large number of methods in his research: court statistics, observation, collection of personal data of members of juvenile gangs, as well as interviews. Thrasher observes juvenile gangs through an ecological paradigm developed by the Chicago School of Sociology. Gangs are the product of the structural and environmental consequences of the social disorganization that took place in Chicago. Juvenile gangs have sprung up in isolated and impoverished immigrant neighborhoods of Chicago. Gangs were part of the psychological and group processes among adolescents in these neighborhoods.

                       Anthropological Approach to City

Lynd Helen and Robert Lynd conducted two empirical studies in a small town (Muncie) in the state of Indiana, in the USA. The results of those studies are presented in the books Middletown (1929) and Middletown in Transition (1937). Helen and Robert Lynd studied the entire society in that city. The methodological approach they used in conducting the empirical part of the research was influenced by the British school of structural-functionalist anthropology. In the first study, they studied six different activities of people: patterns of household organization, the way children are raised, the jobs people do, participation in religious activities, participation in other community activities, and the way people spend their free time. They concluded that the jobs that people did, that is, whether they belonged to the business or the working class, decisively influenced all other types of activities, and even belonging to different Protestant denominations. The second study was conducted during the period of the Great Depression when there was a sudden impoverishment of the working class, but there was no organized class activity of workers.

Robert Redfield advocated a "rural-urban continuum" approach. Instead of viewing rural communities in isolation from the wider civilization, he believed that there was a continuum, from small communities to the largest cities. Although the inhabitants of cities are more secular and individualistically oriented, there are no clear lines of separation, but continuous changes in the patterns of social organization and values, which go from the smallest to the largest settlements. Trade has in the past connected rural communities with urban communities, while the impact of modernization and urbanization has only further connected these settlements and communities.

William Lloyd Warner is known for applying an anthropological approach to research in American society. Warner wanted to apply the way he studied kinship, marriage, social solidarity, and religious life among Aborigines to the study of small communities in the United States. The first such research was conducted in the late 1930s in a small town in the state of Massachusetts (that city is known by the nickname given to it by Warner - Yankee City), using interviews, surveys, observations, and document collection methods. Warner hypothesized that the role that kinship plays in tribal society, in modern society, is taken over by social stratification because stratification affects economic relations, sense of identity and belonging to a community, value systems, and forms of solidarity. He was primarily interested in status stratification, which determines the level of privilege, specific rights, and duties of members of a certain class and their patterns of living. The results of the research are presented in the book The Status System of a Modern Community, 2 vols. (1941, 1942). In the city where he conducted his research, Warner identified six specific classes: upper-upper, lower-upper, upper-middle, lower-middle, upper-lower, and lower-lower. The upper-upper class consisted of "patrician aristocrats", the richest families who possessed wealth for generations; they possessed specific patterns of social interaction and behavior, and they lived in the biggest houses and the best part of the city. The lower-upper class was made of families that experienced upward economic mobility and were sometimes richer than some upper-upper class families, but because their wealth was considered "new", those families did not have the same social reputation. In some other cities, where there is greater upward and downward economic mobility, these two classes formed a single class. The upper-middle class consisted of families who had a small family business, or individuals who were employed as highly-paid professionals. This class formed the basis of political and civic participation in the community. The lower-middle class of owners of small private businesses and highly skilled workers and the upper-lower class, made of skilled workers, made up the majority of the population and had a large dose of inter-class solidarity. The lower class consisted of unskilled workers living in poverty. Warner discovered another type of stratification in the "city of the Yankees", and that was ethnic and racial stratification. Whites and blacks formed two separate "castes," and that caste division intersected class divisions diagonally, and decisively influenced patterns of interaction.

                 Urbanism as a Critique of the Modern City

Lewis Mumford The influence of the Chicago School of Sociology is visible in his commitment to convince politicians and urban planners to pay attention to how architectural and urban solutions and plans affect the social ecology of urban neighborhoods. He wanted to avoid the anomie and loss of the organic community that would result from poor planning of cities and their neighborhoods. As the biggest problems of urbanism, he saw the excessive concentration of the population in huge skyscrapers, the disappearance of public places and parks, and the excessive construction of roads and car parks. Mumford believed that technological advances in transportation and communications would lead to the proliferation of social networks and the strengthening of democracy at the regional level. In the books The Culture of Cities (1938) and The City in History (1961), Mumford explores how the development of cities, urbanism, and architecture, as well as technology, has influenced other social, cultural, and economic patterns.

In The Death and Life of Great American Cities (1961) Jane Jacobs challenged mainstream positions on urban planning and socioeconomic development from an evolutionary perspective. She opposed social engineering, and universal urban strategies; and advocated for diversity, cities that are suitable for humans, and small-scale developmental initiatives. In The Economy of Cities (1969) and Cities and the Wealth of Nations (1984) Jacobs researched historical and archaeological data to demonstrate that cities always have throughout all history been the driving force ushering the economic development. In Edge of Empire: Postcolonialism and the City (1996)  she developed the concept of “representational cities,” which refers to messages encoded in the environment of the city, that can be read as texts. 

Henri Lefebvre made a huge contribution to the development of rural sociology, and later in his career, he made an even greater contribution to urban sociology. His books The Right to the City (in French 1968), From the Rural to the Urban (in French 1970a), The Urban Revolution (2003, in French 1970b), The Right to the City II - Space and Politics (1972b) and The Production of Space (1974) are the most important books with urban sociology as a topic. He believes that the city is the best place to study capitalism, due to the degradation capitalism brought to the city. Capitalism, through speculation with land and real estate, extends commodification to living space. In addition, the capitalist organization of urban space creates segregation of social groups, and this has the most negative impact on the working class. The city should be studied on three levels of analysis: global (as a space shaped by the capitalist mode of production), mixed (as a mediator between the state and everyday life of people), and private level (the everyday life of people in private space). In the historical dimension, the city has gone through three phases: a political city, a commercial city, and an industrial city. With the arrival of socialism, we would enter the fourth and final phase of the development of the city, and through the "urban revolution" a humane urban society would be created. Lefebvre sees urban space as a place where the state and capitalists want to commercialize space (in which technocrats dealing with architecture, urbanism, and planning play a significant role), but also as a place where opponents of this situation want to create alternative spaces - "Heterotopias" - for self-realization through art, communes and similar forms. The urban revolution is the culmination of this defense of the "right to the city".

Castells studied the topics of the city and urbanism. He believed that conflicts and decision-making processes have the greatest impact on the organization of urban space. The basic research question, for him, is how the relations of social groups, which have different interests, shape the housing and infrastructure policy of the city. Castells believes that in monopolistic state capitalism, the state apparatus directly intervenes in favor of big capital by investing in collective consumption at the city level (housing, education, health, parks, cultural facilities), thus reducing labor market reproduction below market prices. In his opinion, the focus of interest should be the process of urban planning. Castells also studies social movements. In his works from the 1980s, he saw the source of the urban social movements in the impossibility of reconciling the demands for the concentration of labor in the city centers and the increasing costs of maintaining urban collective consumption. In Dual City: Restructuring New York (1991) he showed that New York City became a “dual city,” with distinct spatial separation between skilled workers who worked in specialized industries, and immigrants who worked lower-paying service jobs.

               Approach to City of Radical Geography

David Harvey In his book Social Justice and the City (1973), he applies the principles of radical geography and Marxist political economy to explore cities and urbanism. Harvey believes that the urban-rural dichotomy is not identical to the division into modern and traditional. The same cities and life in them have differed throughout history, and in addition, different types of cities have existed within the same mode of production, just as there have been similar types of cities within different modes of production.

He believes that, therefore, when studying cities, it is better to use the term "mode of economic integration" instead of the term mode of production. The concept of mode of economic integration refers to how reciprocity, redistribution, and the market are interconnected within an economic system. When studying the modes of economic integration, the most important aspect is the surplus value that arises within the economy. Cities were created through extraction, mobilization, and geographical concentration of surplus value. Companies always influence the creation and functioning of markets, which are based on the relative rarity of goods and services. Exploitation and appropriation are inherent in the market, so government intervention is necessary to mitigate these destructive market tendencies.

Harvey's book Boundaries of Capital (1982) explores different flows of capital. Marx believed that there would be an excessive accumulation of capital in the industrial sector due to the increase in the organic composition of capital. Harvey believes that the concept of land rent is important for understanding the development of the industrial sector. Firms are building their industrial complexes in locations that will allow them to save on transportation costs or provide lower labor costs. Since these locations are mostly on private land, the increase in land rent, which is due to the increase in demand for land, reduces the early savings of companies. Over time, the profit rate in the industrial sector decreases, so capital moves from the primary (industrial) to the secondary flow of capital. Secondary capital flows are funds that financial institutions invest in fixed capital. The secondary flow of capital is key to understanding urban growth under capitalism. Funds from this flow of capital are invested in the construction of residential and commercial buildings and traffic infrastructure in urban areas, so these investments are becoming a new form of fixed capital. Secondary capital flows also require the development of tertiary capital flows - in the fields of education, science, and technology - in order to increase or maintain profits in primary and secondary capital flows. Over time, the economic crisis spills over from the first to the second flow of capital, as real estate overproduction and depreciation of fixed capital occur. In such situations, banks and construction companies move their investments from those urban locations where the profit rate has been reduced to new locations that have the potential to bring in higher profits. The complex interrelationships of financial institutions, the construction sector, and the real estate market, which are motivated by the race for profit, create a dynamic system of urban development. Such a dynamic system of urban development always creates significant social consequences and new social geography.

Mike Davis, in City of Quartz: Excavating the Future in Los Angeles (1990), argued that globalization and privatization of public space in Los Angeles opened urban land markets to global capital which led to the exclusion of the lower and middle classes from accessing the majority of urban spaces.   

In Postmodern Geographies (1989) Edward Soja, a geographer and urban theorist,  presents his theory of three urban spaces. This framework was developed to understand the complex relationships between physical space, social interactions, and the politics of urban environments. It examines how cities are structured and experienced in contemporary urban environments. His theory divides urban spaces into three distinct but interconnected dimensions:

First Space – The "real" physical space: This refers to the material, spatial layout of the city – the streets, buildings, parks, and other physical infrastructure. It’s the tangible, objective space that people can directly interact with and navigate. This is the space that urban planners, architects, and engineers primarily deal with when designing cities.

Second Space – The representational space: This is the space of imagination, symbolism, and meaning. It includes how people perceive, represent, and experience the city through their cultural, social, and psychological lenses. It's the symbolic and ideological meanings attached to spaces, such as neighborhoods, monuments, or even informal spaces like parks or street corners. The second space is also connected to how different social groups use, claim, or contest urban space, often in ways that reflect broader power dynamics, identities, and struggles.

Third Space – The lived space: This is a synthesis of the first two, blending both the physical and symbolic aspects of space with the lived experiences of individuals. Soja argued that the third space is a more dynamic, fluid, and evolving concept. It's the space where people actively engage with the environment, navigate social relations, and create new meanings. It's the everyday space of experience and social action, where the material and the imagined intersect. The third space is also seen as a site of potential for social change, as it can challenge the norms and structures of the first and second spaces. Soja’s theory highlights the complexity of urban spaces and the importance of considering all three dimensions when studying or planning cities.

                Racism and Discrimination in the Cities

In the book, The Truly Disadvantaged: The Inner City, the Underclass, and Public Policy (1987), William Julius Wilson re-emphasizes the importance of race for the life chances of African Americans and presents data on the highly vulnerable position of urban poor African Americans. In the late nineteenth and early twentieth centuries, African Americans began to move from the rural south to the industrialized north of the United States. Lacking qualifications, they performed the worst industrial jobs and had no chance of advancing. Their poverty and physical isolation in the ghettos led to an increase in white prejudice, which further worsened the position of African Americans. A further deterioration in the situation of a large number of African Americans occurred in the early 1960s, due to several structural factors. The decrease in the number of well-paid jobs in the manufacturing sector in cities, and at the same time the increase in low-paid service jobs, contributed to the reduction of employment, but also to the reduction of real wages of those who were employed. This led to impoverishment, so there was an increase in crime among the male population, as well as an increase in the number of people sentenced to prison terms. The consequence of that was an increased number of single-parent families, in which only the mother was present. This disadvantaged group of African-Americans becomes “the underclass”, economically and socially excluded from wider society.

John Rex One of his most significant studies on racism is the book Race, Community and Conflict (1967), which he co-authored with Robert Moore. In this book, the authors explore how institutions and the process of rising real estate prices have influenced the creation of "housing classes". Housing classes denote a situation in which racial and ethnic minorities live in isolated urban areas where there are inadequate housing conditions. Such housing isolation only increases racial discrimination and the poor economic situation of ethnic and racial minorities. In the book Colonial Immigrants in a British City: A Class Analysis (1979), Rex and Sally Tomlinson showed, based on statistics and their own research, that there are two different labor markets in Britain: the primary labor market is characterized by high wages, good working conditions, job security and the possibility of advancement; while the situation on the secondary labor market is completely different. Immigrants who had the status of racial minorities were far more represented in the secondary labor market in Britain. These immigrant workers did not identify themselves with white workers and their culture but considered themselves a separate, unprivileged class. Rex advocated for clear political and social measures to improve the situation of these populations and warned that the absence of such measures could lead to racially based conflicts.

                                          Global Cities

Saskia Sassen introduced the notion of the global city into sociology in her book The Global City: New York, London, Tokyo (1991). Global cities are the focal points of the organization of the global economy; they are centers of financial firms and firms specializing in special services; they are innovation production centers in the most profitable industries, and they are large markets for products and innovation. These cities are globally integrated, with each other. They have undergone major changes in the structure of economic branches, spatial organization, and social structure. Global cities differ from earlier cities in that the modern economy has a greater need for centralized control and management. These cities are centers of financial and banking innovation and services, marketing, accounting, and legal services, and the largest users of these services are transnational companies. These economic sectors represent the largest source of income and economic power of global cities.

Transnational companies, even if their center is not in one of the global cities, are becoming more and more attached to them. The networked relations of global cities are a source of global control that separates these cities from the scope of control of the countries in which they are located. At the same time, as these cities become more networked and dependent on each other, so they become more separate and independent from the state. Global cities usually have large and culturally diverse immigration from all over the world, so this multiculturalism makes them even more global. When Sassen set out to explore global cities, she singled out New York, London, and Tokyo, and in her book Sociology of Globalization (2006) written 15 years after the first book, she estimated that there were about forty global cities.

Sassen singles out three levels where changes are taking place in the age of globalization: local, state, and global. At the local level, great socio-economic changes are taking place, as many old industries and areas in which they were concentrated are declining, and new areas with new and more profitable industries are strengthening. The biggest change, especially in more developed countries, is the decline in the importance of classic industries - mining, textile production, production of consumer goods, machinery industry, and the like. These jobs, which previously gave durability and security of employment and income to manual workers, as well as the possibility of creating influential unions, are disappearing and are being replaced by insecure and poorly paid jobs in service industries.

These changes, at the state level, lead to the creation of increasing economic differences between regions and individuals, which conditions migration to cities and areas experiencing economic growth. As global cities rise, so do other, less developed areas. At the global level, there are growing inequalities between the countries of the center and the countries of the periphery; there is an increase in immigration from the periphery to the center; and the weakening of the influence of nation-states in relation to global cities. Nation-states do not lose their significance completely, but the concept of sovereignty and territoriality is changing crucially. Sassen calls this process "deterritorialization of national territory".

References:

Abrams. Towns in Societies: Essays in Economic History and Historical Sociology (1979);

Abu-Lughod. New York, Chicago, Los Angeles: America's Global Cities (1999);

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