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Rankings / Scoring/Criteria

An annual investigation of cities progress toward sustainability is the cornerstone of the Smarter Cities project. We sought the advice of academic, non-profit and government experts to come up with a broad set of criteria by which to measure and compare sustainability efforts in cities across the U.S. The ranking scheme, developed with the help of a scholar from Yale’s School of Forestry and Environmental Studies, was intended as a tool for identifying, for the purpose of spotlighting, those cities that are taking the lead in addressing the major environmental challenges of our time, from global warming to clean air and water. 

In the sections below, we describe the criteria and the scoring methodology used in the 2008 rankings. Understanding that they are imperfect tools, we are creating an open source forum to gather together comments and suggestions on ways to improve both. We look forward to your involvement in that discussion.

Scoring

Criteria

Disclaimer

The information contained in this publication is intended for general use, to assist public knowledge and discussion and to help improve the sustainability of urban environments. It includes general statements based on scientific research. Readers are advised and need to be aware that this information may be incomplete or unsuitable for use in specific situations. NRDC is continually working to improve this research tool and welcomes comments on the methodology as well as recommendations for additional data sources at smartercities@nrdc.org.

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How We Scored the Cities

1. In our data collection phase, we sought out comprehensive data sets from the EPA, the U.S. Census and other inclusive datasets that addressed our criteria. See Data Sources and Point System for a full list of databases consulted.

2. To supplement this data, we sent online survey invitations to the mayor's offices or the environmental officers in every U.S. city with a population of 50,000 or more, a total of 655 cities. We received 160 responses to the survey, a response rate of 24.3%. Cities that did not complete the survey were assessed based on the information from governmental and nonprofit databases alone.

3. The data and survey responses provided us with an overview of city performance across the range of our nine sustainability criteria. Within each criterion, we judged performance according to several factors, awarding up to a maximum of ten points per criterion. Green Building, for example, was judged based on the numbers of Energy Star-rated buildings (2 points possible), number of LEED-certified buildings (up to 4 points, with a bonus point for LEED-platinum), use of an alternative green building system (1 point) and the deployment of a sprawl reduction strategy (2 points). We also included a section on Innovation for cities to tell us more about their unique sustainability initiatives and programs. Due to the subjective nature of this criterion, cities received 5 points for a response. Including all the criteria, the maximum possible score was 95 points. For a full explanation of the points accorded each criterion, see Data Sources and Point System.

4. Although all cities were scored according to the same criteria, we recognize that cities of various sizes face different problems and have vastly different resources to draw upon. To reflect these differences, we separated our cities into three population categories. Small cities—with populations from 50,000 to 99,999 people—made up the majority, a total of 408 cities. Medium cities—with populations from 100,000 to 249,999—comprised a total of 178. Large cities—with populations of 250,000 and over—made up our smallest group, totaling 67 cities. From each group, we then selected the top 15 cities to highlight accomplishments among cities of all sizes.

5. Scores for the top fifteen large cities ranged between 83.86 points for Seattle, Washington to 62.725 for Columbus, Ohio. Within the top fifteen medium cities, scores ranged from 72.105 for Madison, Wisconsin to 56.625 for Everett, Washington. Among the smallest cities, the top 15 scores ranged from 71.93 for Bellingham, Washington to 49.54 for Denton Texas. The top 15 larger cities, with greater resources to draw from, performed better across all of the criteria, but that is not an indication that small and medium cities suffer from greater environmental degradation. Larger cities are able to build more green-certified buildings, provide a wider range of energy initiatives to their populations and offer more transportation alternatives—factors that enhanced their scores.

6. In order to feature important distinctions between cities based on criteria, we also provide lists of the top-ranked large, medium and small cities within each criterion. All cities and criteria are compared in our CityGrid, which gives an at-a-glance comparison between cities. For more, see "How To Use The CityGrid" immediately below.
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How To Use The CityGrid

To provide a quick overview of cities' performance in all the categories, we created the CityGrid. In its default view, the CityGrid displays the top 15 large cities (those with populations of 250,000 or more) in their overall rank order. Reading across the grid gives a summary of individual cities' performance in all the criteria. Reading down the grid shows how cities compare to one another within individual criteria.

The "high," "medium," or "low"scores identified by the orange circles indicate that cities scored in the top 10% in that criteria (a high score), the top 25% (a medium score) or the lower 75% (a low score). In three cases—Energy, Water, Environmental Standards—"high" indicates that cities scored in the top 5%, "medium" in the top 10% and "low" in the bottom 90%. This was necessary in these three criteria because all scores in the lower 90% were equal due to the lack of survey response.

Note that the CityGrid is designed to provide a broad overview of the performance of U.S. cities, not to give a detailed breakdown of each city's overall rank.

The CityGrid can be sorted by city or criteria. To see cities displayed in the order of their performance in an individual criterion, click on the criterion icon at the top of the chart. The city overall rank number will remain the same, but the list will be reordered with the cities that received the highest scores in the selected criteria at the top. In both the CityGrid and the Top Ten lists, tied criteria scores were broken using the overall ranking scores for the tied cities.

Clicking on "Show All" in the drop-down tab will display all cities in the size category you are viewing. To view the cities in the other size categories, click on "Medium Cities" or "Small Cities" in the sub-navigation bar below City Rankings (at the top of the page).

City names link to their Smarter Cities card and from them to their city profile page.
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Data Sources and Point System

For each of the Smarter Cities criteria, we sought comprehensive datasets, which we supplemented with survey responses. Below is a list of the databases consulted, data factors used and the maximum points alloted for performance within factors. Points for data within each criterion add up to 10, except for Innovation, which had a maximum of 5 points possible.

Air Quality

Energy Production and Conservation

  • US DOE Green Power Network and Survey: Top three fuels used for power generation (6 points)
  • Survey: Energy conservation incentives offered (2 points), green power offered by utility (2 points)

Environmental Standards and Participation

  • Survey: Number of city department that have environmental standards incorporated into their policies (7 points); provision of environmental commissions on which citizens may served (3 points)

Green Building

  • USGBC LEED Project Directory: Number of total LEED-certified buildings (4 points) and any number of LEED-platinum buildings (1 point)
  • EPA Energy Star: Any number of Energy Star-rated buildings (2 points)
  • Survey: Use of an alternative green building certification system (1 point); sprawl reduction strategies (2 points)

Green Space

  • Survey: Total number of different types of greenspace, including athletic fields, city parks, community gardens, public gardens, trail systems, waterfront and other (6.5 points); presence of an integrated pest management plan (1 point)
  • Survey and Research on web sites: percentage of land that is green space (2.5 points)

Innovation

  • Survey: Innovative policies or practices with supporting documentation (5 points)

Recycling

  • Survey: Total items included in recycling program (3 points); total items picked up by recycling program (3 points); public recycling bins (1 point); percentage of waste diverted from landfill (2 points)
  •  EPA Municipal Solid Waste State Data and Earth 911 were consulted on occasion to check survey responses.

Standard of Living

Transportation

  • Survey: Number of green commuting options for citizens including bicycle paths, bike sharing, bus system, carpool lanes, car sharing, dedicated bicycle lanes, light rail, park and ride, sidewalks and trails, subway, trolley and other (8 points)
  • American Public Transportation Association: documented ridership for public transportation (2 points)

Water Quality and Conservation

  • US EPA Safe Drinking Water Information System:  Health-based violations (3 points); reporting-based violations (3 points)
  • Survey: Water-conservation incentives including rebates, tax credits, conservation pricing and other (4 points)

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The Sustainability Criteria Used in Smarter Cities 2008 Research

Air Quality

From London's deadly fogs to the heart-attack inducing smog of Los Angeles, poor air quality is one of the oldest and most recognized environmental problems confronted by cities. In this study, we examined data from the Air Quality Index (AQI) produced by the EPA.  This index takes into account measurements of ground level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide and particulate matter.  The daily score assigned corresponds with the highest (most detrimental to health) level of any one of these pollutants that day.  The AQI values are broken into different ranges to indicate the various levels of air quality, with lower values indicating better quality. In our analysis, median AQI scores for the first quarter of 2008 were used as a broad measure of air quality within each city.  AQI scores exist for cities nationwide and are consistently produced, making them the best available tool to assess air quality for comparison within the United States.

Smoking was the second major factor in the air quality analysis for each city Less smoking allowed in public places such as workplaces, restaurants and freestanding bars scored more points for a city. We used information from the  Americans for Nonsmokers' Rights database to compile these statistics.
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Energy Production and Conservation

Global warming has made the commitment of local governments to renewable energy all the more pressing.  Half of all the energy produced in the U.S. is derived from coal, the use of which results not only in greenhouse gas emissions, but also mercury emissions that end up in our waterways and in the fish we eat. We asked cities to identify their three greatest electricity-generating fuel sources.  Renewable energy options were broadly categorized as hydroelectric, solar, wind and geothermal power, while all other fuel sources including coal, oil, natural gas, nuclear power and biomass were considered non-renewable.  Points were deducted for the use of nonrenewable power sources, while points were awarded for renewable power sources. Why did we deduct points here? Because we wanted to account for the ongoing environmental damage caused by nonrenewable energy sources while simultaneously highlighting the importance of creating a renewable power system.

The survey also addressed incentive programs for energy conservation within homes and businesses, and whether or not green power options are available to consumers through their local utilities.
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Environmental Standards and Participation

One important measure of a city government's commitment to improving its environment is the inclusion of environmental standards in departmental policies. Cities that address topics such as no idling policies, recycling procedures, and integrated pest management are making clear statements about their priorities. Cities that move to formally include such measures in their written policies are demonstrating a clear long-term commitment to achieving better environmental performance.

Citizen participation is also central to protecting and enhancing urban environments.  Providing opportunities for citizen involvement in environmental initiatives takes advantage of skills and knowledge available in the community and helps residents gain first-hand experience of challenging issues in their hometowns. Survey responses helped us assess opportunities for citizenry to have a voice in the decision-making process.
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Green Building

Buildings typically consume very high amounts of energy, generating half of the greenhouse gases emitted in the U.S. Constructing the spaces in which we spend our lives not only strains resources, but also eliminates habitat, farm land and our architectural heritage. Many cities, however, are finding ways to green their buildings and develop neighborhoods in a less destructive manner.

The most widely used eco-friendly architecture standards in the country are those of the Leadership in Energy and Environmental Design (LEED) program of the United States Green Building Council (USGBC).  We turned to USGBC's database of registered projects to assess the total number of certified buildings in each city.  Points were awarded for the presence of buildings certified at any level—baseline certification, silver or gold—and an additional point was awarded for those cities with buildings that had reached the most stringent level—platinum. 

We also used the U.S. Environmental Protection Agency's Energy Star building database to award points to cities with buildings certified by this alternative system, which focuses on energy-efficient construction. And to recognize that there are many other local and regional programs, cities were also awarded points if they used any other green-building-certification program.

By vastly increasing commuter distances, the sprawl characteristic of many U.S. cities magnifies the global warming impact of buildings. Sprawling developments also do little to enhance a sense of community, often remaining "dormitory suburbs" lacking in green space and public spaces. Furthermore, the additional miles of roads and parking lots contribute to storm water runoff, harming water quality. We gave points to cities with sprawl-reduction strategies in recognition of the long-term benefits they provide.
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Green Space

From the City Beautiful movement of the late-nineteenth century on, the importance of green space to the health and happiness of city dwellers has long been recognized.  City governments were asked what types of green spaces their citizens had access to, including athletic fields, city parks, public gardens, trail systems, and waterfronts.  Responses were scored based on the total number of different types of space that were present.  Respondents were also asked to quantify their city's commitment to green space by providing estimates of the total acreage of green space relative to the total city area, which helped us calculate percentages for urban green space. Finally, we asked if the city had an integrated pest management plan to avoid exposing residents to potentially hazardous pesticides used on urban plantings.
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Recycling

Recycling is a conservation effort that consumes on average a tenth of the energy to produce goods from virgin materials. It's also one of the most visible commitments to the environment that a city can make. This category was assessed using survey data alone.  First, cities were asked if they had a functioning recycling program.  Respondents indicated which items their city recycles from a list that included aluminum, cardboard, garden waste, glass, hazardous materials, paper, plastic, and tin.  Cities were also asked which of these items could be recycled through curbside pick-up services and if they provided recycling bins in public places. Additional points were awarded according to the percentage of total municipal waste recycled.  Cities did not receive any points in this category if they did not fill out the survey.
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Transportation

Providing a range of less-polluting public transportation options is one of the most important actions local governments can take to mitigate climate change and promote cleaner, safer cities. Our survey focused on this issue by asking respondents what transportation options were available to residents.  These included bicycle paths, bicycle sharing programs, bus systems, carpool lanes, car sharing, dedicated bicycle lanes, light rail, sidewalks/trails, subways and trolleys. Statistics on public transit ridership were also gathered from the American Public Transportation Association. However, because these ridership statistics covered only small number of the cities surveyed, they were not heavily weighted for scoring.

One result that may surprise readers is Los Angeles' high rank. Due to the weighting of transportation options, Los Angeles scored well, even higher than New York (by a fraction of a point) though both have made many of the same public transportation choices.
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Standard of Living

The affordability of a city is critical to its sustainability—without livable wages, the advantages of green space and other environmental benefits may be priced out of reach for many. We looked at housing affordability, poverty and home ownership data.  The United States Census Bureau provided data on the median household income, the percentage of families living below the poverty line and the percentage of owner-occupied housing. The National Association of Home Builders Housing Opportunity Index (HOI) was also assessed for each city. The HOI is a number that tallies the total amount of homes sold in a city that would have been affordable to a family earning the median income in that area.  This index is calculated using median income statistics from the U.S. Census and real estate industry data on home prices.
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Water Quality and Conservation

Along with air quality, water quality is one of the most widely recognized problems besetting cities, to the point that bottled water sales have been driven in part by the widespread belief that tap water may not be safe to drink. Water quality was assessed using the EPA's Safe Drinking Water Information System (SDWIS).  The SDWIS data system contains violations of the Safe Drinking Water Act dating back to 1993.  Each city's water supply is listed along with violations for health infractions and violations for reporting and monitoring non-compliance.  Cities were scored based on the number of violations they had in each category.  Data were assessed over the past five years.

Our survey also allowed cities to report on water conservation incentives, including rebates, tax credits, and conservation pricing.
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