For our version, we decided to look at both the density of people and the density of building development. Analyzing census-tract data from the American Community Survey and spatial data from satellite imagery, we created a rural-suburban-urban density continuum index for more than 70,000 neighborhoods in the continental United States.
We evaluated how many people lived in each census tract in proportion to the land mass, and measured the development density by analyzing the pixels from satellite imagery.
A scale of 1 to 10
The satellite imagery, published by the Multi-Resolution Land Characteristics consortium, portrays the United States mainland as millions of tiny dots. Each dot is color-coded to represent a different land use — like forest land, farmland, pavement and buildings. For every census tract on the continent, we counted the dots and measured the percentage representing developed land.
We then converted the percentages to a 1-to-10 scale, and did the same with each tract’s population per square mile. We then combined the two factors into a single index representing the combined density of people and buildings. For neighborhoods with unusual divergences between the two factors — industrial parks that were heavily paved but that had low population density, for example — we always assigned the higher index score.
We categorized the tracts that scored 1 or 2 as rural, and those that scored 9 or 10 as urban.
Everything in between was suburbia, although we eventually divided the suburbs into two groups as well. The reason? When we started running the numbers for demographics and 2016 election results, we realized that the more-dense suburban tracts were, as a group, far different from the less-dense tracts.
We called less-dense suburbs “outer ring,” and denser suburbs “inner ring.”
The comparison totally ignores political boundaries, and intentionally so. In this world, the consideration is the density of neighborhoods, so we observe that 99 percent of New York and San Francisco residents live in urban density, but only 60 percent of Phoenix residents do, as well as 17 percent of Indianpolis residents and 4 percent of those who live in Jacksonville.