How we crunched the numbers
To assemble our database, we looked at all 1.7 million car listings on cargurus.com from August 2 to December 16, 2023. The local popularity of vehicles was ranked not by a model's total number of listings in a particular county but by calculating how much its local listings exceeded its average across all counties nationwide. To weed out anomalies, we considered only counties with at least 400 car listings, and only car models that appeared at least 400 times nationally. (In calculating political popularity, we included models that appeared at least 250 times nationally.)
Cars were included in a county's listings if they appeared in a ZIP code associated with that county. For example, a car in Massachusetts listed for sale in 02149 would be included in the listings for both Middlesex and Suffolk counties, portions of which fall under the ZIP code.
Political scores for each vehicle were calculated using the results of the 2020 presidential election. We included only counties that were strongly red or blue — those where either Donald Trump or Joe Biden won by at least 19 percentage points. We then placed car models in those counties on a political spectrum of reddest (-1) to bluest (+1). Car makers whose models appeal to the widest range on the spectrum — spanning the two political extremes — were rated the purplest brands.
Text by Mark Healy, founder of Flipturn Creative Studios. Data by Andrew Thompson, creator of Components, a cultural research project.