There is perhaps no more vexing issue for urban policy makers than sprawl. And yet, there’s little consensus on how best to accurately measure it. It’s one thing to impugn the phenomenon for contributing to everything from long commutes, congested highways and worsening air pollution to growing segregation, poverty, obesity and mounting health problems. But it’s another to actually gauge the connection between sprawl and that daunting list of social and economic ills.
A new study by Thomas Laidley, a sociology doctoral student at NYU (where I also hold a research appointment), uses satellite images to develop a new and improved “Sprawl Index,” which he links to a wide range of outcome measures. Laidley uses these aerial images (see above) to estimate sprawl at the Census block level, the smallest level available, estimating the share of metro population in those blocks below three key thresholds: 3,500, 8,500, and 20,000 persons per square mile. His index is based on the average of these three values, with higher scores reflecting higher levels of sprawl.