[charles-salvia]

You're right - the 80% is exaggerated. I got it from https://www.census.gov/geo/reference/ua/urban-rural-2010.htm.... Their definition of "urban" is actually outlandish, in that it includes "urban clusters", which means towns that have > 2,500 and < 50,000 inhabitants. I assumed the 80% just included all the sprawling, dense suburbs, but I see the definition the census is using here is much looser.