The human species was born on the plains of Africa, but in the millennia since, we’ve come to make cities our home. According to the United Nations, more than 50% of the world’s nearly 7 billion people now live in urban areas, and the rate of urbanization is accelerating. By 2050, of the 9 billion people living on Earth, 6.5 billion will be city dwellers — more than 70%.
Recent data from the 2010 U.S. Census show important trends within the bigger data points: Cities now represent 80.7% of the U.S. population, and the majority of growth is in central, urbanized areas — they now hold 71.2% of residents, versus 68.3% in 2000. At the same time, rural areas were home to a falling percentage of population, 19.3% compared to 21% a decade earlier.
This is good news for U.S. city centers that have come back to life after decades of neglect. Many urban areas now feature higher-wage jobs and rising real estate values. However, growth can require hard choices, particularly when it comes to housing and transportation. More people mean more cars, the number-one source of traffic congestion and the direct and indirect cause of tens of thousands of deaths every year in the United States. Some cities have addressed these issues by increasing incentives for bicycling, controlling automobile parking and even building new streetcar systems.
While many cities are doing well, the benefits are not always evenly distributed. As city-center incomes have risen, poverty has shifted into the suburbs and rural areas. Economic inequality in the U.S. has also risen significantly in the last 30 years: The Brookings Institution notes that “after declining in the 1990s, the population in extreme-poverty neighborhoods — where at least 40% of individuals live below the poverty line — rose by one-third from 2000 to 2005-2009.” For more studies in this particular area, see the post “New Views on Urban Communities and Poverty in the U.S.: Research Roundup.”
The research on cities and their development is still evolving. “Scholarship on cities is extensive, but our knowledge of urbanization is fragmented,” Karen C. Seto of Yale and William Solecki and Peter J. Marcotullio of Hunter College write in a 2013 paper. “Cities are places. Urbanization is a process, one of simultaneous transformation of places, populations, economies, and the built environment that creates an urban society. Despite a panoply of researchers studying cities, research on urbanization has not focused on the process and its intersection with other environmental systems.”
Below is a selection of studies related to cities and urban trends both in the United States and the world. It has sections on economics, mobility, environment, crime, health and demographics.
“Regenerating America’s Legacy Cities”
Mallach, Alan; Brachman, Lavea. Lincoln Institute of Land Policy, May 2013.
Abstract: “Eighteen legacy cities from among 50 that had a minimum population of 50,000 in 2010 and a loss of 20% or more from peak population levels were selected for analysis using 15 indicators to measure population change, socioeconomic conditions, housing markets, and economic activity. The analysis reveals dramatic differences in the cities’ levels of recovery, particularly during the past decade. While these cities have lost most of their manufacturing bases and central functions , many have begun to regain vitality and rebuild important new economic roles…. Intentional strategies are needed to unlock the potential of a city’s assets to bring about sustainable regeneration. The proposed model of “strategic incrementalism” begins with leaders sharing a vision of the city’s future and then making incremental, tactical decisions that will transform the status quo, while avoiding grandiose and unrealistic plans.”
“The 2050 City: What Civic Innovation Looks Like Today — and Tomorrow”
Black, Alissa; Burstein, Rachel. New America Foundation, June 2013.
Abstract: “‘Civic innovation’ aims to transform our nation’s cities by strengthening the relationship between citizens and their local governments in order to improve lives. But there is little common understanding of this field or its potential. Based on nearly 20 interviews with government leaders, researchers, technologists, community organizers, foundation professionals and others, this white paper explores the current landscape and future potential of the civic innovation field as a first step toward bringing together disparate communities to identify needs, develop solutions and deepen democracy. It finds that while technology can empower civic innovation, technology does not drive it. Furthermore, concentrating on technology can alienate many in the civic innovation ecosystem.”
“Local Multipliers and Human Capital in the United States and Sweden”
Moretti, Enrico; Thulin, Per. Industrial and Corporate Change, 2013, Vol. 22, issue 1, 339-362.
Abstract: “We show that every time a local economy generates a new job by attracting a new business in the traded sector, a significant number of additional jobs are created in the non-traded sector. This multiplier effect is particularly large for jobs with high levels of human capital and for high-technology industries. These findings are important for local development policies, as they suggest that to increase local employment levels, municipalities should target high-technology employers with high levels of human capital.”
“U.S. Cities, Skills and Wages”
Florida, Richard; Mellander, Charlotta; Stolarick, Kevin; Ross, Adrienne. Journal of Economic Geography, June 2011. doi: 10.1093/jeg/lbr017.
Findings: Jobs that require analytic and social intelligence skills, which benefit from “clustering,” tend to concentrate in larger, denser metropolitan areas. In addition, skills are a much better predictor of wages than education level: “While the return to a college education has remained relatively flat between 1999 and 2008, the return to skills has more than doubled.” Analytic and social intelligence skills are also positively correlated with higher wages: “Even when we control for other factors affecting regional wages, such as population, density, human capital, industry structure and immigration, the variables for analytical and social intelligence skills remain strong and statistically significant.”
“Do Colleges and Universities Increase Their Region’s Human Capital?”
Abel, Jaison R.; Deitz, Richard. Federal Reserve Bank of New York, October 2009.
Findings: Metropolitan areas with higher levels of degree production tend to have higher numbers of people in human capital intensive occupations. In particular, the share of people working in the life, physical and social sciences in a metropolitan area is positively associated with degree production. This is also true of metropolitan areas that spend significant amounts of money on research and development.
“Culture Shocks and Consequences: The Connection Between the Arts and Urban Economic Growth”
Pedroni, Peter; Sheppard, Stephen. Working paper, April 2012.
Abstract: “Is there a relationship between local arts and culture production and local prosperity that is permanent rather than transitory? The answer to this question determines whether arts and culture production generates economic growth or a temporary ‘multiplier’ effect that diminishes over time…. In this paper we provide a model that allows us to think systematically about the problem and an empirical methodology capable of testing relevant hypotheses concerning possible answers to the question. We identify data to which these methods can be applied, using per capita GDP and expenditure levels of arts and culture production by not-for-profit organizations in U.S. urban areas. Our analysis suggests that the impact of arts and culture production is not transitory. Shocks to local arts and culture production generate impacts that alter the local economy and change steady-state GDP.”
“Economic Impact of Stadiums and Teams: The Case of Minor League Baseball”
Agha, Noal. Journal of Sports Economics, October 2011. doi: 10.1177/1527002511422939.
Findings: The presence of certain types of minor league teams and new stadiums may increase income in a community, albeit by modest amounts. Per capita income was raised $67 by the introduction of a new Triple-A team and $118 by a High-A team. In addition, building a new Double-A stadium was associated with a $161 increase in per capita income and a new rookie league stadium was associated with a $202 increase. No significant effect was found for the introduction of a Double-A, Single-A, Low-A, rookie league, or independent league team. Similarly, no significant effect was found for a new Triple-A, High-A, Single-A, Low-A or independent league stadium. Overall, there were no significant negative income effects associated with any team or stadium type. In other words, where the measurable impact was not positive, it was neutral and not statistically significant.
“The Fundamental Law of Road Congestion: Evidence from U.S. Cities.”
Duranton, Gilles; Turner, Matthew A. 2011. American Economic Review, 101(6): 2616-52. doi: 10.1257/aer.101.6.2616.
Findings: The number of vehicle-kilometers traveled (VKT) increases in direct proportion to the available lane-kilometers of roadways. The additional VKT traveled come from increased driving by current residents and businesses, and migration. Building new roads and widening existing ones only results in additional traffic that continues to rise until congestion returns to the previous level. Such attempts to “cure” congestion are thus both expensive and ineffective. Increasing the lane kilometers for one type of road does not significantly reduce congestion on others — for example, widening highways does little to reduce local congestion. Metropolitan areas appear to construct new lane-kilometers of roadway “with little or no regard for the prevailing level of traffic.”
“Missed Opportunity: Transit and Jobs in Metropolitan America”
Berube, Alan; Kneebone, Elizabeth; Puentes, Robert; Tomer, Adie. Brookings Institution, May 2011.
Findings: Nearly 70% of residents of large metropolitan areas have access to transit of some kind. Overall, city residents have better access than those living in suburbs. During morning rush hour, residents of the 23 largest metropolitan areas had an average transit frequency of less than 10 minutes. On average, transit frequency in cities was twice that in suburbs. About 33% of high-skill jobs can be accessed by transit within 90 minutes, compared to 25% of low- and middle-skill jobs. Residents of low-income suburban communities fared even worse, with only 22% having access to jobs in low- and middle-skill industries.
“Health Risks and Benefits of Cycling in Urban Environments Compared with Car Use”
Rojas-Rueda, David; de Nazelle, Audrey; Tainio, Marko; Nieuwenhuijsen, Mark J. British Medical Journal, August 2011. doi: 10.1136/bmj.d4521.
Findings: The study is based on four years of data from the bike-sharing program in Barcelona with over 180,000 cyclists. The researchers found that the program increased the number of bicycle trips by city residents by 30%. Of these, 60% had shifted from being regular public transport users, 30% from regular walkers, and 10% from relying on their cars for transportation. Compared with residents who drive, those using the city’s bike-sharing system experienced an annual increase in 0.03 deaths from traffic accidents and 0.13 deaths from air pollution. However, as a result of increased physical activity, 12.46 deaths were avoided annually, meaning that overall, the program helped prevent 12.28 deaths per year. The program was calculated to have reduced overall CO2 emissions by approximately nine million kilograms annually.
“Risk of Injury for Bicycling on Cycle Tracks Versus in the Street”
Lusk, Anne C; et al. Injury Prevention, February 2011. doi:10.1136/ip.2010.028696.
Findings: The study examines the relative safety for users of physically separated two-way bicycling paths, known as cycle tracks, and in-street cycling. The researchers found that cycle tracks were used by 2.5 times more cyclists compared to nearby on-street bicycle routes. The relative risk of injury was 28% lower on cycle tracks compared to nearby on-street routes. The safest cycle tracks were on streets that experienced the least amount of vehicular traffic, while those on high-traffic streets saw fewer or the same number of injuries as alternative routes that were also in heavy traffic areas.”
“Report on Curbside Motorcoach Safety”
National Transportation Safety Board, October 2011, SR-11-01, PB2011-917002.
Findings: Compared to automobiles, travel by bus is relatively safe. “During 2009, the bus occupant fatality rate was 45 deaths per 100,000 accidents compared with 251 deaths per 100,000 accidents for passenger car occupants.” However, from January 2005 to March 2011, curbside carriers had 1.4 fatal accidents per 100 vehicles compared with 0.2 per 100 vehicles for conventional bus carriers — seven times the rate of fatal accidents. In part because of the buses’ size, most of the victims were occupants of other vehicles. Smaller and more recently established curbside carriers were less safe than those that had larger fleets and a longer operational history. Those with 10 or fewer motorcoaches and in business for 10 years or less had higher rates of both accidents and roadside inspections and violations.
“The Racial/Ethnic Distribution of Heat Risk-Related Land Cover in Relation to Residential Segregation”
Jesdale, Bill M.; MorelloFrosch, Rachel; Cushing, Lara. Environmental Health Perspectives, May 2013. doi:10.1289/ehp.1205919.
Findings: “After adjusting for ecoregion and precipitation, and holding segregation level constant, non-Hispanic blacks were 52% more likely (95% confidence interval (CI): 37% to 69%), non-Hispanic Asians 32% more likely (95% CI: 18% to 47%), and Hispanics 21% more likely (95% CI: 8% to 35%) to live in [heat risk-related land cover] conditions compared to non-Hispanic whites. Within each racial/ethnic group, HRRLC conditions increased with increasing degrees of metropolitan area-level segregation…. Land cover was associated with segregation within each racial/ethnic group, which may be partially explained by the concentration of racial/ethnic minorities into densely populated neighborhoods within larger, more segregated cities. In anticipation of greater frequency and duration of extreme heat events, climate change adaptation strategies, such as planting trees in should explicitly incorporate an environmental justice framework that addresses racial/ethnic disparities in HRRLC.”
“Going Green Together? Brownfield Remediation and Environmental Justice”
Eckerd, Adam; Keeler, Andrew G. Policy Sciences, December 2012, Vol. 45, Issue 4, 293-314. doi: 10.1007/s11077-012-9155-9.
Findings: Brownfield sites are more likely to be in communities that are both poor and predominantly minority. Sites in communities with a higher proportion of minority residents move more slowly through the assessment phase of cleanup than those in other neighborhoods, and even sites located in comparatively poorer areas progressed more quickly than those in neighborhoods with a higher proportion of minority residents. The probability that remediation will be undertaken and its speed appear to be influenced by economic factors.
“Tree and Impervious Cover Change in U.S. Cities”
Nowak, David J.; Greenfield, Eric J. Urban Forestry & Urban Greening, 2012.
Findings: In the cities examined, tree and/or shrub cover ranged from a high of 53.9% in Atlanta (2005) to a low of 9.6% in Denver (2009). The highest rate of impervious surface coverage was 61.1%, in New York City (2009), and the lowest 17.7 %, in Nashville (2003). The highest rate of building surface area was 27.1% in Chicago (2005) and the lowest in Kansas City, 4.8% (2003). Roads, parking lots and other impervious surfaces covered 36.2% of Miami and just 12.3% of Nashville (both 2003). Over the periods studied, cities’ tree, shrub and soil cover generally fell, while other categories of cover tended to increase. “Nineteen of the 20 cities analyzed showed a reduction in tree cover, 17 of those cities had a statistically significant net reduction.”
“Analysis of Health, Safety and Greening Vacant Urban Space”
Branas, Charles C.; et al. American Journal of Epidemiology, July 2011, doi: 10.1093/aje/kwr273.
Findings: Lots converted into green space throughout the city studied, Philadelphia, were strongly correlated with a lower rate of gun assaults during the study period. Rates of vandalism and criminal mischief also declined in one section of greened city lots studied. “Vacant lot greening was associated with residents reporting significantly less stress and more exercise in select sections of Philadelphia.” The authors suggested that the new greened lots were seen as safe recreational spaces by residents, and social differences in each neighborhood may have impacted green space use.
“What Is a Tree Worth? Green-City Strategies, Signaling and Housing Prices”
Wachter, Susan M.; Bucchianeri, Grace Wong. Real Estate Economics, summer 2008, Vol. 36, No. 2, 213-239.
Abstract: “We investigate the correlation between curbside tree plantings and housing price movements in Philadelphia from 1998 to 2003, comparing two programs, one by the Philadelphia Horticultural Society (PHS) that requires block-group effort that focuses on low-income neighborhoods and the other by the Fairmount Park Commission that is individual-based without specific target areas. A 7 to 11% price differential is identified within 4,000 feet of the Fairmount tree plantings. We argue that this is largely driven by either social capital creation or a signaling mechanism, on top of an intrinsic tree value (around 2%).”
“Property Values, Parks, and Crime: A Hedonic Analysis in Baltimore, MD”
Troy, Austin; Grove, J. Morgan. “Property Values, Parks and Crime: A Hedonic Analysis of Baltimore, MD,” Landscaping and Urban Planning, August 2008, 233-245.
Findings: When the crime rates of parks or similar amenities are relatively low, they have a positive impact on property values. When the crime rates cross a threshold of between 406% and 484% of the national crime average, however, they begin to have a negative impact. Park size was unrelated to crime level, with all sizes of parks in the high, medium, and low crime categories. Parks located near water also varied widely according to crime levels, “suggesting that [water] amenities do not always yield positive impacts on property.” The location of high- and low-crime parks across Baltimore was found to be widely dispersed throughout the city. “Often, low-crime parks will be found very near high-crime parks without intermediate medium-crime parks in between.”
“Go Where the Money Is: Modeling Street Robbers’ Location Choices”
Bernasco, Wim; Block, Richard; Ruiter, Stijn. Journal of Economic Geography, 2012, 1-25. doi: 10.1093/jeg/lbs005.
Findings: A robbery was more likely to occur when the location is close to the robber’s home. For “each log-kilometer” a block was to a robber’s home, it was “5.32 times more likely to get selected for robbery.” The existence of certain kinds of businesses on a given block was associated with a higher likelihood of being selected for robbery: bars, clubs, fast food restaurants, hair salons and barbershops, liquor stores, groceries, gas stations, Laundromats, pawn shops, and check cashing places. This is likely because these places conduct a substantial amount of transactions in cash. The race of the robber had a strong effect on what areas they decided to target. African-American robbers were 1.98 times more likely to target a majority African-American block; Hispanic robbers were 3.82 times more likely to target a majority Hispanic block; and Caucasian robbers were more likely to target a predominantly white block.
“Homicide as Infectious Disease: Using Public Health Methods to Investigate the Diffusion of Homicide”
Zeoli, April M.; Pizarro, Jesenia M.; Grady, Sue C.; Melde, Christopher. “Zeoli, April M.; Pizarro, Jesenia M.; Grady, Sue C.; Melde, Christopher. Justice Quarterly, October 2012. doi: 10.1080/07418825.2012.732100.
Findings: In this study, researchers tracked homicides in Newark, New Jersey, from January 1982 through September 2008. Approximately two-thirds of homicide victims and over three-quarters of offenders were African-American males from 26 to 30 years old. They found that gang-related homicides were concentrated in areas of the city already suffering from higher-than-average homicide rates before they spread to adjacent areas. At the same time, there is a small census tract flanked by areas with high levels of gang activity that reported no gang-related homicides during the study period. The North and East Wards, which have remained relatively immune to the elevated homicide rates of adjacent wards, are comparatively wealthy and home to a lower percentage of African-Americans.
“Subsidized Housing, Public Housing and Adolescent Violence and Substance Use”
Leech, Tamara G. J. Youth and Society, June 2012, Vol. 44, No. 2, 217-235. doi: 10.1177/0044118X10388821.
Findings: Teens living in housing subsidized by vouchers have a 9% lower violence rate, 8% lower prevalence of heavy marijuana or alcohol use, and a 5% decrease in other drug use compared to teens living in public housing projects and in non-public housing. Adolescents living in public or subsidized housing were 31% less likely to engage in violent behavior compared to those living outside public housing. No significant effect of living in public or subsidized housing was found relating to the use of alcohol, marijuana or hard drugs compared to similar teens not receiving housing assistance.
“City Living and Urban Upbringing Affect Neural Social Stress Processing in Humans”
Lederbogen, Florian; et al. Nature, May 2011.
Findings: Previous studies show that city dwellers have a 21% greater risk for anxiety disorders and a 39% increased likelihood of mood disorders. MRI scans showed that increased exposure to urban environments was associated with increased activity in the brain’s amygdale region, which is involved in emotions such as fear and the release of stress-related hormones. For those who lived in cities for the first 15 years of life, the MRI showed increased activity in the perigenual anterior cingulate cortex, which plays a role in regulating the amygdale region of the brain. Those raised in the city are thus more likely to have a permanently raised sensitivity to stress than those who moved there later in life.
“Women’s Well-being: Ranking America’s Top 25 Metro Areas”
Lewis, Kristen; Burd-Sharps, Sarah. Social Sciences Research Council, Measure of America, 2012.
Findings: Women in Washington, D.C. ($37,657), San Francisco ($35,380) and Boston ($31,503) earned significantly more annually than their counterparts in Riverside-San Bernardino ($22,306), Pittsburgh ($23,557) and San Antonio ($24,961). The 2012 poverty guideline for a family of four in the continental United States is $23,050. Women tended to earn more in areas where a higher percentage of women were unmarried. Educational attainment and enrollment accounts for much of the differences in wages. Close to 20% of women in Washington, D.C., hold an advanced degree compared to only 6.9% of those in San Bernardino. “In Pittsburgh, Boston and Minneapolis-St. Paul, only about 6% of young women ages 25 to 34 did not complete high school, the best outcome on this indicator among the 25 cities. In contrast, in Riverside-San Bernardino, Los Angeles and Houston, that rate is almost 17%, nearly three times the rate among the top three.”
“Collective Efficacy and Major Depression in Urban Neighborhoods”
Ahern, Jennifer; Galea, Sandro. American Journal of Epidemiology, April 28, Vol. 173, Issue 12, 1453-1462. doi: 10.1093/aje/kwr030.
Findings: Neighborhoods with lower collective efficacy — a measure of their social cohesion and informal social control — were associated with a higher rate of depression. Residents in neighborhoods in the lowest quartile of collective efficacy had a 5.3% rate of major depression compared to a 2.5% rate among the neighborhoods with the highest collective efficacy. The degree of collective efficacy had the largest impact on residents 65 years of age or older. For those living in neighborhoods with high degrees of cohesion and control, the rate of major depression was estimated to be 2% for seniors. But under low collective efficacy conditions, the rate of major depression was 8.2% for seniors.
“Gentrification and Low Income Neighborhoods: Entry, Exit and Enhancement”
Ellen, Ingrid Gould; O’Regan, Katherine M. U.S. Census Bureau Center for Economic Studies Paper No. CES-WP-10-19, September 2010.
Findings: The key drivers of neighborhood change were voluntary entries and exits — not forced economic displacement — and differences between the incomes of those moving into and out of gentrifying neighborhoods proved not to be significant. Original homeowners — immune from the effects of rent increases — left gentrifying neighborhoods at significantly higher rates than did poorer households that rented. The researchers suggested that relocation may be more a selective choice than a product of mounting economic pressures.
“End of the Segregated Century: Racial Separation in America’s Neighborhoods, 1890-2010”
Glaeser, Edward; Vigdor, Jacob. Manhattan Institute for Policy Research, January 2012, No. 66.
Findings: As recently as 50 years ago, 20% of America’s urban neighborhoods had no black residents. Today, African-Americans can be found in 99.5% of neighborhoods nationwide. In 1960 nearly 50% of the black population lived in neighborhoods with an African-American share above 80%. Today, only 20% of the black population lives in a neighborhood where the African-America population is above 80%. In all but one of the nation’s 658 housing markets, the separation of black residents from other races is now lower than the national average in 1970. Segregation continued to drop in the last decade, with 522 out of 658 housing markets recording a decline.
Keywords: research roundup, cars, bicycling, crime, creative class, gentrification