Concentrated poverty refers to a spatial density of socio-economic deprivation. In the US it is commonly used in fields of policy and scholarship in reference to areas of "extreme" or "high-poverty" defined by the US census as areas with "40 percent of the tract population living below the federal poverty threshold." A large body of literature argues that these areas of concentrated poverty place additional burdens on poor families that live within them, beyond what the families own individual circumstances would dictate. The research also indicates that areas of concentrated poverty can have wider effects on surrounding neighborhoods, not classified as "high-poverty," limiting overall economic potential and social cohesion.

History of the Measure and the Concept

The Invention of the Measure

There have long been areas of concentrated poverty, and the distinct social problems of concentrated poverty, which exacerbate individual impoverishment have been the grounds of reform movements and studies since the mid-19th Century. However, the the measure of concentrated poverty and the coalescence around an analytical conception of concentrated poverty occurred only in the 1970s. This more recent focus on concentrated poverty grew largely out of concern about the nation’s inner cities in the wake of ongoing deindustrialization, civil unrest in the late 1960s, and the rapid suburbanization and out-migration that followed. In most cases, these poor inner-city locations were populated predominantly by minorities, and many featured large public housing developments.

The definition for "low-income areas" first developed by the Bureau of the Census as part of its work for the newly established Office of Economic Opportunity, a new bureaucracy designed to administer most of the War on Poverty Programs created as a part of Lyndon B. Johnson’s Great Society legislative agenda . The goal was to identify areas of major concentrations of poverty within large metropolitan areas. The original definition was formed through an attribute-based criterion. Each census track was ranked by an equally weighted measurement of (1) an areas income, (2) level of education, (3) number of single-parent households, (4) percentage of low-skilled workers, and (5) quality of the housing stock. The lowest quartile from the rankings were then designated "low income." The 1970 census took the earlier attribute-based measure and translated it into a purely statistical one - defining "low-income areas" as census tracts with 20%-39% of its inhabitants falling below the poverty and designating areas of "high-poverty" or “extreme poverty” as those with 40% or more of its inhabitants falling under the poverty line. The 20% threshold adopted in 1970 was derived by calibrating a statistic of household income that most closely approximated the 1960 lower quartile. The 40% threshold to designate "high-poverty areas" was set by doubling the low-income threshold. . This 40% threshold became the common definition of "concentrated poverty" in policy and scholarly research.

Another measure of concentrated poverty used for larger geographical areas was later developed by Paul Jargowsky. His rate expresses the proportion of all poor individuals in a certain area (e.g., city, metropolitan region, or county) who live in census tracts of high poverty. Later, Jargowsky uses the concept of concentrated poverty to refer more specifically to the "proportion of the poor in some region city or region that resides in high-poverty neighborhoods" as opposed to a territorial designation of high-poverty neighborhoods
The Invention of the Concept

The first major work of scholarship to utilize the census measure to study the changing spatial trends of poverty, as well as its causes and effects, was William Julius Wilson in his book The Truly Disadvantaged: The Inner City, The Underclass, and Public Policy. His findings revealed that poverty increased dramatically, not only in Chicago, but throughout metropolitan areas of the United States during the 1970’s, as did the population of poor people residing within them. These trends related specifically to an African American "underclass" in America's inner city (see trends below). In this work, Wilson utilizes concentrated poverty as an analytic measure to gauge the changing spatial organization and intensification of poverty, as a territorial category to designate an object of analysis and, and also as a causal factor in and of itself, effecting life chances among the poor. All three of these conceptualizations have since served as the basis for a wide range of social science research as well as policy interventions and prescriptions.

Wilson's study set the precedent of using the census' 40% threshold and this has been adopted as the standard measure to study trends of poverty and poor neighborhoods (for the few exceptions see the critiques). As a territorial category, areas of concentrated poverty have become both key targets of place specific policy interventions as well as the object of analysis for comparative studies in policy research and the social sciences. As explored more fully in the section on effects, concentrated poverty has increasingly been recognized as a "causal factor" in compounding the effects of poverty by isolating residents in these neighborhoods from networks and resources useful to realize human potential.
Critiques of the Measure & Concept

Critiques of the measure have been leveled against both the federal definition of poverty as well as the census definition of concentrated poverty by the 40% threshold. Criticisms of the definition of poverty are legion, the most salient being the inability to fully consider the needs of different family types (eg: the need for childcare services, health insurance, etc), the non-cash benefits from public sources, the cash and non-cash resources or lack-there-of from social and familial networks, and the consideration of regional variations in cost of living expenses. At the same time, the 40 percent benchmark used by the census and scholars to define concentrated poverty does not refer to any adequately specified objective or subjective criteria. Jargowsky and Bane (1991) assert “...that the 40 percent criterion came very close to identifying areas that looked like ghettos in terms of their housing conditions” (p. 239). They contend that “the areas selected by the 40 percent criterion corresponded closely with the neighborhoods that city officials and local Census Bureau officials considered ghettos” (p. 239). Thus, these scholars argued that although “any fixed cutoff is inherently arbitrary...the 40 percent criterion appropriately identifies most ghetto neighborhoods” (p. 239). Here we see that the use of the threshold is justified on the basis of a general personal impressions and impressions of city officials rather than any rigorous objective criteria.

Aside from the contention over the selection of a particular percentage threshold as an accurate descriptive measure (ie 30% vs. 60% threshold of residents in poverty), other scholars have criticized the use of an absolute indicator of poverty concentration as an analytic measure and tool to track trends. For instance, Massey and Eggers contend that a relative indicator based on segregation is more rigorous and meaningful, claiming that ". . .levels and trends in poverty concentration are best studied with well-established measures of segregation that use complete information on the spatial distribution of income instead of an ad hoc and arbitrary definition of 'poverty neighborhoods' and 'poverty concentration'"

Jennifer Wolch and Nathan Sessoms have challenged the utility of the traditional concept of concentrated poverty based on the 40% threshold due to the recent growth of working poor populations and the emergence of inner-suburban poverty. . Their study shows that several areas in Southern California, which meet the 40% threshold do not demonstrate the characteristics traditionally associated with areas of concentrated poverty and not suffer from extreme levels of dysfunction, crime, and blight, but are often reasonably clean, safe, well-maintained and home to several commercial/retail establishments, public facilities, etc. They also argue that the term has become conflated with "areas of social problems" and argue that the concept should be unhooked from behavioral definitions and stigma.

Loic Wacquant has criticized the measure when used to denote or define “ghettos.” An explicit move first made by Bane and Jargowsky and implicit one among others, scholars increasingly conflate the two, which Wacquant claims camouflages the constitutive role of ethnoracial domination in the ghetto and hyperghetto (Forthcoming, 2012).

Effects

Several recent studies have pointed to the role of "neighboorhood effects" caused by concentrated poverty. These studies have illustrated that crime and delinquency, education, psychological distress, and various health problems, among many other issues, are affected by neighborhood characteristics, particularly the concentration of poverty. Thresholds, or tipping points, also prove important . In a recent review of research, Galster notes that studies suggest “that the independent impacts of neighborhood poverty rates in encouraging negative outcomes for individuals like crime, school leaving, and duration of poverty spells appear to be nil unless the neighborhood exceeds about 20 percent poverty, whereupon the externality effects grow rapidly until the neighborhood reaches approximately 40 percent poverty; subsequent increases in the poverty population appear to have no marginal effect.” Housing values and rents show a similar pattern. Using data from the 100 largest U.S. metro areas from 1990 to 2000, Galster, Cutsinger, and Malega find little relationship between neighborhood poverty rates and decline in neighborhood housing values and rents until poverty exceeds 10 percent, at which point values decline rapidly before becoming shallower at very high poverty levels Geoge C. Galster, Jackie M. Cutsinger, and Ron Malega. 2008.

One of the largest studies examining the effects of concentrated poverty was completed by the Pew Economic Mobility Project which tracked 5,000 families since 1968 and found that no other factor, including parents' education, employment, or marital status, was as important as neighborhood poverty in explaining why African-American children were so much more likely to have lower incomes than their parents as adults. Thus, the concentrated poverty rate aims to capture the extent of a possible “double burden” imposed on poor families living in extremely poor communities; both being poor and living in a poor community. The study also found negative effects on the better-off children raised in such areas, as well. There has been a large literature of scholarship produced to identify the negative neighborhood effects of concentrated poverty as well as the mechanisms through which they transpire. Below is an overview of these effects and mechanisms.
Neighborhood Effects of Concentrated Poverty
(From George C. Galster, "The Mechanism(s) of Neighborhood Effects: Theory, Evidence, and Policy Implications).

Social Interactive Effects

This set of mechanisms refers to social processes endogenous to neighborhoods. These processes include:

• Social Contagion: Behaviors, aspirations, and attitudes may be changed by contact with peers who are neighbors. Under certain conditions these changes can take on contagion dynamics that are akin to “epidemics.”
• Collective Socialization: Individuals may be encouraged to conform to local social norms conveyed by neighborhood role models and other social pressures. This socialization effect is characterized by a minimum threshold or critical mass being achieved before a norm can produce noticeable consequences for others in the neighborhood.
• Social Networks: Individuals may be influenced by the interpersonal communication of information and resources of various kinds transmitted through neighbors. These networks can involve either “strong ties” and/or “weak ties.”
• Social cohesion and control: The degree of neighborhood social disorder and its converse, “collective efficacy" may influence a variety of behaviors and psychological reactions of residents.
• Relative Deprivation: This mechanism suggests that residents who have achieved some socioeconomic success will be a source of disamenities for their less-well off neighbors. The latter, it is argued, will view the successful with envy and/or will make them perceive their own relative inferiority as a source of dissatisfaction.
• Parental Mediation: The neighborhood may affect (through any of the mechanisms listed under all categories here) parents’ physical and mental health, stress, coping skills, sense of efficacy, behaviors, and material resources. All of these, in turn, may affect the home environment in which children are raised.

Environmental Effects

Environmental mechanisms refer to natural and human-made attributes of the local space that may affect directly the mental and/or physical health of residents without affecting their behaviors. As in the case of social-interactive mechanism, the environmental category can also assume distinct forms:

• Exposure to Violence: If people sense that their property or person is in danger they may suffer psychological and physical responses that may impair their functioning or sensed well-being. These consequences are likely to be even more pronounced if the person has been victimized.
• Physical Surroundings: Decayed physical conditions of the built environment (e.g., deteriorated structures and public infrastructure, litter, graffiti) may impart psychological effects on residents,

Geographical Effects

Geographic mechanisms refer to aspects of spaces that may affect residents’ life courses yet do not arise within the neighborhood but rather purely because of the neighborhood’s location relative to larger-scale political and economic forces such as:

• Spatial Mismatch: Certain neighborhoods may have little accessibility (in either spatial proximity or as mediated by transportation networks) to job opportunities appropriate to the skills of their residents, thereby restricting their employment opportunities.
• Public Services: Some neighborhoods may be located within local political jurisdictions that offer inferior public services and facilities because of their limited tax base resources, incompetence, corruption, or other operational challenges. These, in turn, may adversely affect the personal development and educational opportunities of residents.

Institutional Effects

The last category of mechanisms involves actions by those typically not residing in the given neighborhood who control important institutional resources located there and/or points of interface between neighborhood residents and vital markets:

• Stigmatization: Neighborhoods may be stigmatized on the basis of public stereotypes held by powerful institutional or private actors about its current residents. In other cases this may occur regardless of the neighborhood’s current population because of its history, environmental or topographical disamenities, style, scale and type of dwellings, or condition of their commercial districts and public spaces. Such stigma may reduce the opportunities and perceptions of residents of stigmatized areas in a variety of ways, such as job opportunities and self-esteem.
• Local Institutional Resources: Some neighborhoods may have access to few and/or high-quality private, non-profit, or public institutions and organizations, such as benevolent charities, day care facilities, schools, and medical clinics. The lack of same may adversely affect the personal development opportunities of residents.
• Local Market Actors: There may be substantial spatial variations in the prevalence of certain private market actors that may encourage or discourage certain behaviors by neighborhood residents, such as liquor stores, fresh food markets, fast food restaurants, and illegal drug markets.

American Trends & Attributes

1970-1990

Between 1970 and 1990 the number of people living in high-poverty poverty neighborhoods - where the poverty rate is 40% or higher - doubled. Because the measure was not used in the US census until 1970, the first time trends of poverty concentration were studied systematically was after the release of the 1980 census. Sociologist William Julius Wilson found that during the 1970’s, (1) poverty increased dramatically throughout metropolitan areas of the United States; (2) at the same time, the number of poor people residing within these areas increased; and (3) this exacerbation of poverty conditions occurred primarily within African American neighborhoods. Several scholars would go onto affirm that in the 1970s America saw a dramatic increase in the number of neighborhoods that classified as areas of concentrated poverty This trend extended to a lesser extent in the 1980s, as the number of neighborhoods qualifying as areas of "extreme poverty" continued to increase, but at a slower rate than it had throughout the 1970s. These trends of concentrated poverty at the level of the census tract and neighborhood were similarly reflected at the level of Metropolitan Statistical Areas (MSA's). In both decades between 1970-1990, the differential between the poverty rates of central cities and their suburbs increased, reflecting an increasing spatial concentration of MSA poverty within central cities. This changing spatial distribution of poverty has been attributed to changes in the labor market (deindustrialization, an increasing gap between wages available to skilled and unskilled workers, spatial mismatch between the types of jobs offered in the city and the type of workers residing there), declining economic growth (although several studies have shown a weak or non-existent link between reduction of poverty and urban economic growth in neighborhoods of extreme poverty), the relocation of upper- and middle-income residents from the city to the suburbs, and demographic changes (the rise in one-parent households and decrease in labor market participation). These changes were intertwined with America's history of ethno-racial segregation that produced the ghetto, white flight from American cities, which led to a declining tax base to provide city services, and the civil rights movement, which allowed better-off blacks to leave inner-city areas .
1990-2000

The number of people living in high-poverty neighborhoods declined by 24% or 2.5 million people, in the 1990s. The steepest declines in high-poverty neighborhoods occurred in metropolitan areas in the Midwest and South. The share of the poor living in high-poverty neighborhoods declined among all racial and ethnic groups. This was especially the case for African Americans, wherein the share of poor black individuals living in high-poverty neighborhoods declined from 30 percent in 1990 to 19 percent in 2000. This decline of high-poverty neighborhoods occurred in rural areas and central cities, but suburbs experienced almost no change.

Scholars have also recognized qualitative shifts in areas of "concentrated poverty." In a study of Southern California metropolitan areas (a state which did see rises in concentrated poverty through the '90s against the national trend), Wolch and Sessoms point to the growing number of working poor populations and the emergence of inner-suburban poverty which qualify as areas of "extreme poverty" under the 40% threshold do not demonstrate the same negative social behaviors or physical decay of the traditional image that the statistic was first designed to designate. Other scholars, have alternatively argued for an expansion of the term and challenge Jargowsky's claim of decreased poverty concentration in the 1990s. Swanstrom et al. have shown that by using the relative definition of poverty as employed in Europe based on 50% of the median income in each region, the '90s actually saw an increase in concentrated poverty through most American cities

(Graphs, Maps, and Tables Forthcoming).