Dante Chinni and James Gimpel, the authors of Our Patchwork Nation: The Surprising Truth About the “Real” America, look at demographic data of the United States at the county level. There are 3,141 counties in the U.S. and though they vary considerably in geographical size and population, using county-level maps to display data provides a convenient way to compare and contrast demographic data.
By mapping demographic data at the county level, you can see how attributes like population density, income, education, attitudes, behaviors, and health are distributed across the U.S.
Unfortunately, the authors take the wonderfully detailed data available from various sources at the county level and use segmentation analysis to group the counties into twelve categories and give them cute names. Ugh.
Our Patchwork Nation. Image from Amazon
Luckily, the authors provide access to the raw county-level data at their website, patchworknation.org. You can view county level chloropleth maps for a wide variety of data. There is even a tool to overlay two maps to do comparisons. The tool doesn’t work very well since you cannot select the colors of the overlays. But overall, the patchworknation site has some of the best U.S. data maps available.
An example of the problem using segments rather than the raw data is illustrated in an article that appears in The Atlantic Apr 2010. The map shown below shows the 12 segments. But the user has to flip back and forth between the legend and the map to determine what each color means.
The 12 states of America. Image from PatchworkNation
The raw data, at the Patchwork Nation website is shown in the three maps below. The first map shows the median household income in 1980. The colors show which quintile each county falls into. The second map shows quintiles for 2010. It is hard to compare the two maps to see how the distribution changes. Going to the Patchwork Nation website and toggling between the two maps makes it easier.
Distribution of median household income by county in 1980. From Patchwork Nation
Distribution of median household income by county in 2010. From Patchwork Nation
The map below shows the change in median income for each county using 2010 adjusted dollars. Notice the counties with large and growing urban populations, mostly on the east and west coasts. They had the highest median incomes in 1980 and in 2010. They also show the highest growth in median income while the remaining counties show smaller gains or a loss. The gap in income distribution in the U.S. is growing.
For more on this story, read the article at the Patchwork Nation website.
Change in median household income by county from 1980 to 2010. From Patchwork Nation