Smart Growth America, a national coalition of public interest groups, seeks to help policy makers better understand urban development patterns through statistical research. In 2002, the organization released Measuring Sprawl and Its Impact, a report examining the costs and benefits of low-density areas.

It has since updated that research with an analysis of 221 metropolitan areas and 994 counties throughout the nation. The report is based on findings published this year by the Metropolitan Research Center at the University of Utah.

Of the most sprawling cities, several in the South top the list. They include the large metropolitan areas of Atlanta and Nashville, and the medium-sized city of Baton Rouge, Louisiana. Several locales in North Carolina were ranked as among the least dense, including Hickory, Raleigh, and Greensboro. But California’s Riverside also ranked near the top of the list.

Measuring Sprawl 2014 evaluates large, medium-sized, and small cities according to their development density, land use mix, street connectivity, and proportion of people and businesses located near each other. Each metro area is ranked according to these four factors, which are combined to calculate a locale’s sprawl index score. Those measuring higher, with an average index of 100, tend to be less sprawling than those with lower scores.

Researchers found that as a metro area sprawled less, the quality of life for its citizens improved. Higher density was discovered to have a strong, direct relationship to upward mobility. Of course, the percentage of income spent on housing is greater in compact cities like New York and San Francisco than in many sprawling areas.

One of the draws of low-density suburbia is the availability of single-family homes that are larger and often more affordable than urban rowhouses and apartments. The study recognizes the cost differential in noting that each 10 percent increase in scoring for compactness is associated with a 1.1 percent increase in housing costs relative to income.

Nevertheless, the research shows that the average percentage of income spent on transportation is smaller in urban-dense areas where there are more options for getting around. Each 10 percent increase in the score resulted in a 3.5 percent decrease in transportation costs. San Francisco residents, for example, spend about 12.4 percent of their income on transportation compared to those in Hickory, North Carolina, who spent 29.1 percent.

Exploring the connections between sprawl and life expectancy, the researchers related health data on the county level to the index scores for those jurisdictions. They found that people living in compact and connected counties live longer, by about three years for an average American. However, denser counties have more car crashes, the report notes, but fewer of those are fatal. For every 10 percent increase in the score, fatal crashes decrease by almost 15 percent.

Living in a compact metro area may also reduce the chances of gaining weight. The researchers found that the body mass index of a population increases as the metro area continues to sprawl. People living in more compact counties have lower blood pressure and lower rates of diabetes.

The report concludes by admitting that the streets, buildings, and landscapes of the scored metro areas affect their quality, but their designs are not part of the study. Perhaps the impact of these settings on everyday life might be a good subject for Smart Growth America’s future research.